June 2010 Cover Page


June 1931  

The Rifleman's Journal
A Collection of Articles Dealing with Rifle Accuracy Topics

Father and Son at Camp Perry - 1931

This Month:
Resizing Changes the Case
Slow Twists and Heavy Bullets
New Neck Turning Tool
Whelen on Long Range Shooting
15 Cents  

.30-06 Day

Happy .30-06 Day!
Today is the day that all fans of the .30-06 celebrate!  Is it the anniversary of the introduction of the cartridge?  No, it's the 30th day of the 6th month: 30-06  (30-06-10 actually).

So, to make the celebration a great one, here are some links to the best information on the .30-06 that you'll find anywhere.  Enjoy the day and and remember Townsend Whelen's great statement: "The .30-06 is never a mistake!"





Sibling Rivalry: .308 vs. .30-06

.30-06 Update

A Short History of the .30-06

The Logical .30-06




Dad Farr and the Farr Trophy

National Match Ammunition (Hap Rocketto)

Eliseo RT10 Tubegun .30-06

This coat belonged to my old friend Jack Bickley, now gone to a better place.  Jack shot the .30-06 at Camp Perry and elsewhere for many years.  He always told me "Better days are coming."  Jack, I know they have for you now.
Bob Jensen, Wimbledon Cup winner, Distinguished Rifleman, legendary Palma coach and ammunition maker and a great friend.  He was such a dedicated .30-06 shooter in the 1960's that he didn't quit until Mid Tompkins took his rifle and rebarelled it to .308 without Bob's knowledge!
Lones Wigger (right) the last Olympic 300 Meter gold medalist (1972) shooting, what else, a .30-06.  That's Joe Farmer next to him, Joe is a pretty dedicated Smallbore shooter so no .30-06 connection with him, but what a wonderful person he is!
Morris Fisher - there was nothing that he didn't win.  Olympic medals, world championships, just name it and he won it.  Fisher is the only person whose accomplishments rival those of Wigger and it was all with the .30-06.  Fisher article.

Enjoy .30-06 day and break out your .30-06, old or new, this weekend.  Nothing could be more fitting for the 4th of July! 



Reloading - Moly Buildup in Seating Die

The following article by Larry Medler is an important one for those of use who use moly-coated bullets.  Larry's website is a treasure trove of information and I am very appreciative of his permission to run this article here.  - GAS -

Past and Present Moly Users
by: Larry Medler

This may or may not apply to you. Lately I have been measuring the force it takes to seat bullets and this set up uses a flat load cell plate on the press ram and not a shell holder. This set up as been working fine for me for the past couple or so years on brass that had been reloaded a few times before measuring the bullet seating force. However, I had to start some new brass and noticed that the cartridge would stick in my Redding Competition Seating Die. I was also noticing some scratching on the bullets after seating. So I decided to take my Redding Competition Seating Die apart and clean in. Wow, what a mess inside the throat of my seating die. I have not been using moly coated bullets for some time but this build up sure looked like moly build up in the seating die. I must admit that I have not very obedient about cleaning my rifle seating dies. So this is just a note to all past and present moly coated bullet uses, you may want to check your seating dies for moly build up. All of my seating dies had some build up. The following picture shows the moly build up in my Redding Competition seating die for my 221 Fireball.


Now for rest of the Story!


That is the first part of this story, check and clean your seating dies. The second part of this story I will keep short. The real story could be a book. I measured the hole in my Redding Competition Seating Dies and my Wilson in line bullet seating dies while cleaning the seating dies. I measured the holes in the seating dies using gage pins. (Actually I was using the gage pins to test if I had hole in the die cleaned) The bullet seating holes in my 308 and 6XC Wilson dies for were one thousandth larger and two thousandths larger for my 223 seating die than the bullet seating hole in my Redding Competition seating dies. Interesting? The Wilson Dies do not use a shell holder. They just have a small plate with a hole in it for primer clearance. After cleaning my Redding Competition Seating dies none my older loaded ammunition would stick in the dies.

However the new brass which I just turned necks on, most of those loaded cartridges would stick in the Redding Seating Die. What causes this? At first I thought my brass which was once fired was sticking in the Redding Seating Die. This brass could have been re-sized one more thousandth. The re-sized brass shows a little bolt closing resistance on some cases. However, the re-sized brass does not come close to sticking in the seating die. The bullet also slides easily through the seating die. Yet seated rounds stick big time. Cause: inside neck wall and outside neck wall not on same center line. The inside neck circle is off center by variation in neck wall thickness. So after turning the necks the hole in case for bullet is still off center a little. That little bit will cause the seated bullet to rub on one side in the seating die. When using a shell holder on the ram the case is easily extracted and any sticking is not noticed. Some rounds just feel different than others.

The Redding Competition Seating Die is very sensitive to any off center bullet conditions with the die seating hole very close to the bullet diameter. So variations in neck wall thickness may be enough to cause one side of the bullet to bind in the seating die and require that a shell holder be used to remove the cartridge after seating the bullet. The Wilson dies are opened up some so most will not stick and the ones that do may be easily removed with a screw driver. That is what the relief cut is for in the bottom of the Wilson Die.

However there might be another use for the Redding Competition Seating Dies and Wilson Seating Dies. If you have both for one caliber, you could use them for a Go and No-Go gauges to check cartridge concentricity. While the die is not in the loading press, simply place ether die over the loaded round so the case shoulder bottoms out in the die. First check some prepped brass without a bullet to see and feel how the empty brass will slip easily in and out of the seating die. Also note how far the brass goes in to bottom out on the case shoulder. Then do the same with a loaded round. Just using your hands press the cartridge completely into the seating die.

If a loaded round sticks hard in a Wilson die – Not very Good

If a loaded round does not stick in a Wilson die and sticks in a Redding die – Okay but not great

If a loaded round does not stick in a Redding Competition Seating Die – About as good as it gets.

Note: Neck turned brass after fire forming should all pass the Redding Die Test. Cases with unturned necks, I am guessing that most of them would show some sticking in the Redding Die. The one standard seating dies I have the hole for the bullet is five thousandths greater than bullet diameter and could not be used to test for concentricity.

Larry Medler

anyrange@comcast.net

Web Address Announcement

I was able to get the domain name http://www.riflemansjournal.com/ and make it redirect to the blog.  As of now, that will bring you here so you don't need to type the "blogspot" part anymore.  I also redirected my old http://www.shootersjournal.com/ name to here since that site has been dead for a long time.

Thanks to Darren Sucato for all the technical work to make this happen!

Good Stuff: Bore Rider Barrel Care Products

Good Stuff: Bore Rider Barrel Care Products
by: Germán A. Salazar

We see new bore cleaning solvents introduced with some regularity, but cleaning hardware evolves more slowly. I’ve been using some new jags from Don Leidich’s Bore Rider Barrel Care Products for a few months and am satisfied that they are a genuine improvement over anything else I’ve used. Don began making these items for the black powder cartridge shooters as their cleaning needs are serious and frequent. He has now expanded the line to include popular bore sizes for modern centerfire barrels.

Modern Jags and Brush Guides Made from Acetron Polymer
Don’s Bore Rider enterprise makes jags as well as companion Brush Guides for use with bore brushes. These are all made from Acetron® GP, an acetal polymer material similar to Delrin, but with greater lubricity. Bore Rider Jags and Brush Guides minimize any damage that might occur to the crown when the jag or brush exits the bore. With conventional jags and brushes, when brushing or patching your barrel, the cleaning rod shaft falls to the bottom of the bore as the patch or brush exits. Over time, that can result in excessive wear at the lower edge of the bore (6 O’Clock position) in the last few millimeters on the muzzle end. In extreme cases you can even wear a slight groove in the lip of the crown (i.e. the very end of the rifling at the muzzle). Another advantage of Bore Rider Jags over conventional brass jags is that you don’t get “false positive” green/blue patch colorations from solvent reactions with the metal jag itself (as opposed to actual copper fouling in the barrel).

The Bore Rider Jag has an extra-long shank so that when the patch exits, the Acetron (polymer) shank is the only thing that makes contact with the crown. This way you don’t have a metal rod tip riding over the delicate crown. The Bore Rider Jag shank diameter is also a close fit to the bore to avoid uneven wear. The Brush Guide is an Acetron extension that fits between your brush and the end of the cleaning rod. This extension protects the crown when you brush, allowing you to push the brush completely out of the barrel without dragging metal connections over the delicate crown. [Editor's Tip: While the polymer material used in the Bore Rider Jag and Brush Guide is "kinder" to crowns, be sure keep the Acetron shanks clean from small particles and debris. These particles can embed themselves in the polymer. Wipe off the Jags and Brush Guides regularly.]

If protecting your barrel’s crown was all that these items did, that would be enough to merit their use. However, what’s more interesting about the jags is that they are made for a very tight fit in the bore and as a result, they truly get the patch working to scavenge the grooves of all the residue possible. The fit is so tight that Don was concerned that not all patches might work properly, as some extra thick ones might not enter the bore at all on this jag. I’ve used the jags with patches from Sinclair, Bruno’s Pro-Shot and a couple of no-name bags and all have worked flawlessly. Also, the jags are designed so that the segments that hold the patch material can never come in contact with the crown while pulling it back into the barrel. My borescope examination of the barrels shows that the job is getting done right.

Source for Bore Rider Jags and Brush Guides
The 6mm and .30 caliber jags sell for $12.50 and the Brush Guides sell for $10.50. These are threaded and chamfered to fit appropriate Dewey rods. The opposite ends on the brush guides have 8-32 female threads. Customers can buy adapters (from other vendors) to fit other brands of cleaning rods. Don will also custom make these to match a customer’s rod specifications if you don’t want to deal with an adapter. Don’s custom made Jags and Brush Guides cost $22 and $18 respectively.

Bore Rider Barrel Care Products
http://www.boreriderbarrelcareproducts.com/
Don Leidich
18855 Nelson Rd.
St. Charles, MI 48655
989-642-5036 evenings
brbcp@yahoo.com


History: The Roumanian Cup

The following piece originally appeared in Volume XIX of The Infantry Journal, which covers the second half of 1921.  It describes the NRA's acquisition of the Roumanian Cup, a trophy still contested at the NRA National Championships.  A complete history of the conditions of the match for the trophy as well as a listing of the winners of the trophy may be seen by clicking here
- GAS -

The Roumanian Cup

Another trophy, won by a team representing the United States Army in the Inter-Allied Games at Paris in 1919, has been added to the list to be in perpetual competition under the direction of the National Rifle Association of America.

On the completion of the rifle and pistol competitions of the Inter-Allied Games, held at the specially constructed range at Le Mans, under the direct supervision of Colonel A. J. MacNab, U. S. A., the Roumanian Government presented to General Paul A. Wolf, Captain of the American Rifle Team, the trophy shown in the pictorial section.

The cup was presented through General Gevanescul and Colonel Bodalescu, of the Roumanian Army, as a testimonial of their appreciation of the courtesy shown the Roumanian Rifle Team prior to and during the Inter-Allied competition.

At the time of the presentation it was requested by the Roumanian representatives that this trophy be put up for annual competition between teams representing the United States Army, Navy and Marine Corps.

In a letter turning over the trophy to the custody of the National Rifle Association, General John J. Pershing said:

Out of deference to its donors and as a recognition of their interest in our services, as indicated by this donation of the trophy, it would greatly please me to have the match, whatever the course comprising it, named "The A. E. F. Roumanian Trophy Match."

In replying to the letter of General Pershing, Colonel Brookhart, President of the National Rifle Association, said, among other things:

I am delighted to accept this trophy on behalf of the National Rifle Association of America. Your request that it be put up as a perpetual trophy for annual competition, at the National Matches, by teams representing the United States Army, Navy and Marine Corps will be granted, and the match will be named "The A. E. F. Roumanian Trophy Match." I want to assure you that it will be received and appreciated as one of the most famous and most desirable of National Trophies.

The conditions of the annual competition will be decided by the National Rifle Association.

As an incident in the presentation of the trophy, it may be interesting to recall that during the Inter-Allied competition, the Roumanian Rifle and Pistol Teams fired with our rifle and automatic pistol.

Preceding the actual match the teams were coached by American officers, especially Colonel MacNab, and so well did the latter do his work that the Roumanian riflemen ran the Canadian team a very close race for third place, and at one point in the match were actually leading the Canadians.

On the 27th of June, 1921, in the presence of the Roumanian diplomatic contingent in Washington, the cup was actually turned over to the custody of the National Rifle Association by General Pershing and has now taken its place alongside the other famous shooting trophies which have done so much in placing Americans on a plane by themselves among the riflemen of the world.


The Roumanian Cup today.

1930's Roumanian Cup medal pendant.

Reloading: Partial Neck Sizing

The question of the month comes from John C. in Australia.


Reloading: Partial Neck Sizing

Good Morning Germán ,


I really enjoy reading your journal, It's very informative.

I have a question for you, but first some information about shooting down here for your interest.

I shoot F Class Standard in South Australia, at the Murray Bridge rifle Club, with a Barnard Model P action, heavy palma Kreiger in .308 1:13" twist, with a stock similar to a Kelbly M1.

A bit of information about Australian F Class. It is in 2 divisions :

Standard - restricted to .308 with 155 gn projectiles, or .223 with 80 gn projectiles (as it is in Full Bore - our equivalent of your Palma), an 8 kg weight limit, 1 kg trigger pull, and restrictions on exactly what powder ( only ADI ) and projectile ( about 4 specified ) you can use. This to a large degree causes the contest to be won by marksmanship and wind reading without too much technology.

Open - calibre 8mm and under, any projectile, any case, 'safe trigger', 10 kg rifle weight limit. This is favored by the more technological types who like to run at the leading edge high BC using the 'best' bullets, powders, cases, barrels etc etc, obviously these blokes have to be able to read the wind as well.

We shoot from 300 meters to 1000 yards, on a modified ICFRA target. With 2 optional sighters and 10 shots to count. We score out of 60, and have just introduced a 'super V' in the centre for countouts etc

I have this quote from your Oct 2009 article on neck tension :

"In the Redding Competition Neck Die with the micrometer top, the bushing can be allowed to move upward, thus limiting how far down the neck it sizes, but there is no practical reason for a Highpower shooter to do this. The Type S dies, like the one shown here, don't have that level of adjustment - and that's no loss."

When I size my .308 Lapua Brass with my Redding Type S Bushing Die, I adjust it so only half the neck is sized with the belief that the unsized portion of the neck is fire formed to my chamber and this ensures that the bullet is centered perfectly in the bore.

Now for my question,

Do you think that this is a valid expectation, and do you think that there are any reasons not to do this?

Thanks a lot,

Regards , John C.


Hello John,


Thanks for writing! Your question is a good one. You're correct that the Type S die can be adjusted to provide partial neck sizing. Unlike the competition neck die which has a spring-loaded collar, the Type S will just let the bushing ride the case mouth up until the top of the bushing stops and then it will size to whatever degree is left.

The real question is whether using the unsized portion of the neck to center the cartridge in the chamber is practical. I think this is not an optimal solution for a few reasons. First, let's consider what we're really after - we want the bullet to get a good, well-centered start in the rifling. Now let's look at a few scenarios to get there.

A case that is only neck sized depends on the case body itself - or at least that's the theory - to center the bullet. In reality, the case is banana shaped to a greater or lesser degree, but always curved and it is highly unlikely that it will actually put the bullet into perfect, straight alignment in the throat. The fully resized neck and a bit of clearance in the throat mean that the bullet is likely pointed off center to some degree, following the curvature of the case.

A case that is full-length sized, but only partially neck sized, which is the condition you describe, depends on the unsized portion of the neck to center the bullet. The resized case body is still banana shaped, but has been sufficiently reduced in diameter at the shoulder to keep the curvature from wedging the case within the chamber. Now, we get to the unsized portion of the neck. There is approximately 0.001" diametrical clearance to the chamber neck on the unsized portion just from normal brass springiness. There is probably no more than 0.0005" diametrical clearance between the bullet and the throat and in many cases as little as 0.0002" clearance. In other words, there is one-half to one-fifth the clearance in the throat that there is in the unsized portion of the neck. Which is doing the alignment? If that were all, we could say there's no harm done by the partial neck sizing, but that isn't the whole story. Unless the bullet is perfectly concentric to the neck, there exists the possibility that the bullet's alignment in the throat is being influenced by the neck's eccentricity in relation to the bullet. If you're relying on two points to align the whole, those two points had better be perfectly concentric. The longer the unsized portion of the neck is, the greater likelihood of the neck inducing a misalignment in the throat due to imperfect neck to bullet concentricity.

Now the last scenario, a full-length sized case in which the neck is also fully sized. There is clearance at the neck and in the body of the case, the closest fit anywhere is the bullet in the throat. If the neck to bullet concentricity is good (although it needn't be perfect), then the bullet will find good alignment in the throat and the case body and neck will have minimal influence. Let's not forget that the base of the case is supported by the bolt face or the extractor to a certain degree as well; this is yet another influence on alignment. As you can see, there are several points from base to bullet that can have an effect. My procedure is to minimize the influence of those that I can control, namely the case body and neck, and let the alignment be dictated by the fit of the bullet in the throat and to some extent by the bolt's support of the base. Barring a seriously out of square case head, I don't think the bolt can have a negative effect on alignment, only a slightly positive effect from minimizing "case droop" in the chamber. Given that a resized case will usually have a maximum of 0.001" diametrical clearance at the web, this isn't much of a factor anyway.

In conclusion, I believe that allowing the bullet to find a relatively stress-free alignment in the throat by full length sizing (including the neck) and turning necks to enhance concentricity gives the bullet the best probability of a well-aligned start into the rifling. Additionally, I place a high value on easy bolt operation and true full length sizing helps that quite a bit. I favor easy bolt operation as a prone shooter because I keep the rifle in my shoulder for the entire string and struggling with the bolt not only can shift the buttplate (always with adverse consequences) but it is also a distraction from my attention to mirage and wind flags which ideally occupies all of the non-aiming time.
 
Germán

History: Long Range Shooting by Whelen

The following article is a chapter on Long Range shooting from Townsend Whelen's famous book Suggestions to Military Riflemen.  The book was published in 1909 when the New Springfield (1903) was indeed new and competitive shooters were learning its features and capabilities.  There is much in Whelen's words that remains valid today and more that is worth reading simply to hear it in the grand gentleman's own words.  The entire book may be accessed on Google books by clicking here- GAS -


CHAPTER XV
Long Range
By: Townsend Whelen
"There are many good short-range men, who have simply not got the necessary brains nor education for first-rate long-range work; and there are very few officers capable of teaching it well, or who ever had half a chance to learn it." — Tippins, in Modern Rifle-Shooting.

The above quotation, from one of the greatest English experts, applies with equal force to our own service. It is not so much that long-range firing differs from short or mid-range work, as that the laws which apply to short and mid-range apply with equal or greater force to long range, and while one or two factors may be disregarded and still not spoil a mid-range score, yet the overlooking of a single thing will play havoc at 1000 yards. It will be seen that to apply all the principles and rules so far laid down in this work requires a thorough knowledge of them, a quick and active brain, good eyesight, and a good body; and also, it might be said, a good education. These are, then, the essential qualities of a good long-range shot. Eliminate any one of these, and we will in all probability eliminate also the good scores.

Long ranges are classified as those between 600 and 1000 yards. Practically, however, there is little difference between the care necessary to make a creditable score at 600 yards and that necessary at 800 yards. The real difference comes when one retires to 1000 yards; therefore the following remarks will pertain more particularly to that range.

The rifle is the first consideration. The muzzle of the bore must be perfect to give the necessary accuracy. The bore must be smooth and free from rough places and rust, which would make it foul quickly with cupro-nickel. The barrel must be kept in perfect condition with the metal fouling solution, as directed in Chapter II.

The rifleman must do his own part perfectly. His hold must be steady and exactly the same at each shot. The same amount of tension should be placed on the gun-sling for each shot, and the elbows should lie in the same holes. The aim should be as correct as the eyes can see to make it. Canting or leaning of the sights must be carefully guarded against, as a hardly visible cant will carry one from the bull's-eye into the "two space" on the target. And lastly, and most important, the pull must be perfect for every shot. The least little unsteadiness or jerk in the trigger-pull will cause a miss almost every time.

Every refinement must be used. The micrometer, telescope, and score-book are especially necessary. One may get an occasional good score without these aids, but his average work will be very poor indeed. By referring to the table on page 86, it will be seen that when using service ammunition and not using the micrometer the radius of the shot group will be about 35.17 inches. Of course, all the shots will not fly as wild as this, but every little while one will, and this one often is a miss, or else it causes one to think his sighting is wrong and plays the mischief with the score generally. Individuals, and organizations shooting at long range without the micrometer will find that scores of 25 to 30 out of a possible 50 is about the best they are able to average. If, however, the micrometer is used, we eliminate the error in sight-adjustment and the radius of the shot group is reduced to about 18.9 inches. The average scores of good shots at 1000 yards under these conditions will be found to run from about 35 to 42 out of a possible 50. Service ammunition made in lots of millions of rounds cannot, of course, have the special attention given to it during manufacture which makes special match ammunition so accurate. Service ammunition gives a mean vertical deviation at 1000 yards of about 8.9 inches, and the special match ammunition used by the American Bisley Team in 1908 gave a deviation of only 5.29 inches. This difference is enough to cause the best shots of the country using the latter ammunition to average 47. to 48 out of a possible 50 at 1000 yards, and with this ammunition perfect scores of 50 at 1000 yards have become very common. Therefore, at long range, to get good results, you must use a micrometer and the most perfect ammunition you can obtain.

A good telescope or powerful field-glass is also essential. Small changes in mirage drift must be watched for, quickly determined; and allowance made for them. This is especially necessary in fish-tail* winds.

*Fish-tail winds are those coming from the general direction of 6 or 12 o'clock, but which are constantly changing from 5 to 7 o'clock, or from 11 to 1 o'clock. The flag flutters from one side to the other continuously, and it only through the glass that one can gain a true estimate.

The score-book is very necessary at long range, in order that one may keep accurate records of elevations and weather conditions. These change so often, and the change amounts to so much at long range, that any attempt to keep these in the head soon results in confusion and drives everyone to the score-book.

You must have a thermometer, barometer, and hygrometer, and must use them, it is not necessary to bring them to the firing-point, but they should be read shortly before firing. A man may use an elevation of 1025 yards at the 1000yard range one day, and the next day his correct elevation may be only 900 yards. If he has no instruments and does not know how to use them, it may take him from five to fifteen shots before he gets a hit on the target. Many men's qualifications as sharpshooters and expert riflemen are ruined from this cause.

A score previously fired at 800 yards does not always give a true indication of what the elevation will be at 1000 yards. Often one will fire and make an excellent score at 800 yards with his normal elevation, and on immediately going back to 1000 yards he may find that at that range he has to use 4 or 5 minutes of elevation above or below normal.

It occasionally happens that elevations worked out according to all the rules are not correct. It is here that the experience of the old and seasoned long-range shot comes in. He seems to know by instinct which way to move to get a hit. About the best way to become proficient at long range is to get such a man for a coach.

In some localities scores at long range will be found to average quite high despite the absence of all refinements. This will be found to be the case where weather conditions vary but little during the shooting season. Thus, in certain parts of the Philippine Islands and in California, and at certain seasons of the year and time of day, the thermometer, barometer, and hygrometer will be found to have almost the same readings day after day. Here the inexperienced shots are able to do very good work at long range. They find the correct elevation, and as long as they keep their rifles clean, and use the same ammunition, they can stick to that elevation during their whole season's practice. On the majority of ranges in our country, however, during the shooting season, we are liable to have changes in temperature of 30 degrees, changes in barometer of 3/4 of an inch, and changes in hygrometer of 40 per cent; and these may make differences in elevation at 1000 yards of 150 yards, or 10 to 15 minutes.

"Unaccountables" are shots which either miss the target or else hit it in a quite different spot from what was expected, and their deviation from the rest of the shot group cannot be accounted for. A true "unaccountable" is usually due to a faulty cartridge, but one has to be a very good shot indeed before he can truly blame a bad shot on the ammunition. Very often unaccountably bad shots are more liable to be small errors in pull-off, small changes in mirage, wind, or light, etc., which have escaped the rifleman's notice. With ammunition giving a large vertical deviation "unaccountables" are more liable to occur than with the more recent accurate loads. One may, for instance, aim a little high without noticing it, and then pull off a little high, and the shot may be one of those striking at the top of the shot group, in which case the shot may go over the top of the target, and lead one to think he has had an "unaccountable" shot when such is really not the case. With the recent great improvement in ammunition and the almost universal use of the micrometer, the word "unaccountable" has almost disappeared from the vocabulary of the really expert shot.

It is of little use attempting to get accurate results at long range when the targets are marked with the big old-fashioned marking disk. One must know exactly where his shot hits the target. The alternative method of marking, with shot marks or "spotters,"* as prescribed in the latter part of Paragraph 103, Small-Arms Firing Regulations 1906, should be used exclusively.

*Spotters are small .30-caliber pegs or nails with a round head of card-board or tin. The spotter is inserted in the bullet-hole of the last shot fired and the card-board head is seen by the rifleman when the target is raised after being marked. Black card-board is used to mark shots which hit in the white of the target, and white cardboard for the bull's-eyes. The card-board should be about 6 inches in diameter for long range and 3 inches for mid range. Field-glasses are needed to see them. This system of marking is used exclusively in the National Matches, and at Camp Perry and Sea Girt.

To sum up, the following precautions should always be used in long-range firing:

1. Keep your barrel in perfect condition.
2. Use a micrometer and the best ammunition you can get.
3. Read the thermometer, barometer, and hygrometer before starting your score, and figure out your elevation.
4. Watch the flags and mirage closely before each shot.
5. Remember that a perfect pull-off only will hit the target.

Basics: Resizing - Case Dimension Changes

Resizing - Case Dimension Changes
by: Germán A. Salazar


When you get home from the range with a box full of fired brass, it's time to get to work.  The most fundamental decision to be made is how to resize the brass - will it be full length sized or neck sized?  Some people believe there is a third alternative: partial full length sizing.  Once you've performed the procedures shown in this article, I think you'll understand and agree that neck-sizing is not suitable for Highpower shooting, that full-length sizing is the best way to resize cases and that the third option is no option at all.  I also hope you will have a better understanding of what goes on inside the resizing die.

Some of the noticeable effects of improper resizing are:
  • hard bolt closing,
  • hard bolt opening after firing rounds that have normal pressure, 
  • a click at the top of the bolt opening stroke with normal pressure loads,
  • early case head separation,
  • damage to the bolt locking lugs,
  • frustration leading to assorted venial sins.
Any one or more of these symptoms may present themselves if a case is improperly sized.  You can oversize a case as easily as undersize it and we'll cover all of the possibilities.  A quick refresher on measuring the case might be useful before we begin, so if you're new to reloading, click here to read an article on basic case measurements.

Let's take a look at what the resizing die does and why it does it.  When you take a shiny new factory loaded cartridge out of the box, you expect it to fit into the chamber of your rifle regardless of whether the rifle and cartridge were both made last week at Remington or if they were made 50 years and two continents apart.  If the cartridge is a .30-06 and the rifle is chambered for .30-06, you have the right to expect them to be dimensionally compatible and amazingly enough, they are.  That compatibility is a result of the Sporting Arms and Ammunition Manufacturers' Institute (SAAMI) having promulgated standardized dimensions for both chambers and cartridges to ensure compatibility.  The cartridge obviously has to be smaller than the chamber and SAAMI standards call for the largest acceptable cartridge to be smaller in all dimensions than the smallest acceptable chamber.

Case and Chamber Compatibility
Below are the standard drawings for the .30-06 cartridge and chamber.  Compare the dimensions and tolerances of a few key points and you'll begin to develop a feel for the clearances specified.





Once you fire that cartridge, however, all of those dimensions change - 55,000 psi has a way of doing that.  The cartridge case expands in every radial dimension on firing until it contacts the chamber walls.  The case also expands longitudinally to bring the case shoulder to bear against the chamber shoulder.  As pressure decreases, the case springs back from its maximum diameter, although not quite back to the unfired dimensions; it does not spring back longitudinally.  That springiness is what allows you to extract the case from the chamber without having to hammer the bolt open.  The brass cartridges case's springiness, while useful, is limited, that's why we can't simply neck size brass forever without running into problems.

If a cartridge is loaded to an excessive pressure level, the rifle will not work as designed.  Assuming the pressure is excessive but not so excessive as to blow out the primer or cause other catastrophic failure of the case or rifle, you will notice that the bolt is hard to open, especially hard to move near the top of the stroke and hard to retract.  What happened is fairly simple: the excessive pressure caused the chamber walls to expand to a degree that allowed the brass to expand beyond its elastic limit, then as the chamber sprung back to normal size, the brass was firmly captured against the chamber walls with no clearance.  Additionally, the locking lugs may have flexed a bit, allowing the longitudinal expansion to be more than normal and also creating an interference condition when the steel sprung back as pressure dropped.  The case is now firmly stuck.

A case that was reloaded to normal pressure level can exhibit many of the same symptoms of an over-pressure case if it was not properly resized.  Just as the over-pressure case creates an interference fit in the chamber, the improperly resized case does not have enough room to expand as the pressure builds and will cause the chamber itself to spring outward slightly, then trap the case as it comes back to normal.  The cartridge case needs room to expand in order to then spring back enough to extract normally. 

Key Dimensions
The four key dimensions that must be resized properly in order to ensure proper chambering and extraction are:
    Base to cone (colloquially headspace) which SAAMI standardizes at 2.0526" -0.0070" for the .30-06.  In other words, there is a 0.007" tolerance towards shorter, no tolerance for longer.  This, of course, refers to new cases.  Headspace will be checked with a gauge from MCS (203) 775-1013.  The numbers shown in the charts below for the headspace dimension are read right from the gauge.  The gauge is calibrated so that a reading of 0 is equal to the SAAMI minimum length for cone to base on the specified cartridge.  In this case, my readings of about 4 indicate that my chamber is 0.004" longer than minimum, or about halfway into the allowable tolerance of 0.010" for that dimension on the SAAMI chamber print.  That's a comfortable place to be as it ensures that the fired case can go into the die far enough to be resized properly.

    Base diameter is standardized by  SAAMI at a point 0.200" from the base.  This is in the solid web area and will not usually change much.  We will examine a point 0.390" from the base; that is closer to the point at which the .30-06 case has maximum expansion.  Not coincidentally, it is where case head separations typically occur on a .30-06 case.  Base measurements will be taken with a blade micrometer. When you put a .30-06 case into a Forster .308 case gauge, the base sticks out just the amount we need for our base measurement; we'll use that procedure to ensure consistent placement of the micrometer.
    Shoulder diameter, standardized by SAAMI at 0.4410" for new .30-06 cases.  Measuring the shoulder diameter can be a bit tricky, but with care, I think we can hit the same spot consistently. This diameter will be checked with the calipers for convenience as it is a slightly less critical dimension than the base diameter and getting a micrometer on the same spot at the shoulder is very difficult. The calipers, although less precise, are easier to get to the same spot and operate with a single hand while the other hand holds the case.


    Case length, standardized by SAAMI at 2.494" -0.020"for the .30-06.

    Each of these case dimensions must be sufficiently smaller than the corresponding chamber dimension to ensure proper functioning.  In most cases, a reduction of 0.002" from fired dimensions to resized dimensions is sufficient for base and shoulder diameter as well as headspace; sometimes less will do, this depends a bit on the pressure at which the cartridge is fired.  Case length must be monitored as it will always grow and can cause serious pressure problems if it exceeds the maximum allowable length.  While neck diameter is also an essential element of case resizing, we're not going to examine that because all methods of case resizing will adequately resize the neck.

    The next illustration is a print of the chamber reamer used to cut my rifle's chamber.  You can see that the shoulder dimension is specified at 0.340" and the base at 0.474".  Given the specified body taper of 0.16237" per 20 inches, the chamber dimension at the point we measured (0.390" from the base) should be 0.471".



    Let's take a look at a set of fifteen cases in some detail.  We will examine the key dimensions before and after neck sizing, full-length sizing and "partial full-length sizing" using five cases for each method.  The test cases are Lake City 62 Match that have been fired four times.
    Neck Sizing  The first five cases were neck-sized only, using a Redding Competition Series neck-sizing die.  Each of the four key dimensions was measured on each case in its as-fired condition (AF) and after being neck-sized (NS).  The average change in each dimension was then calculated and is shown at the bottom of the chart. 

    Although we expected to see no change in the base and shoulder diameters, you will see that there was, in fact, a small but consistent reduction in those dimensions.  The Redding die uses a sliding sleeve to hold the case in alignment with the neck bushing and apparently, that sleeve is very close in size to the chamber of my rifle and was doing a little bit of sizing.  More importantly, we see that there was no change in te headspace dimension and a slight bit of growth which came from reducing the neck diameter.  Every significant reduction in diameter will always be accompanied by an increase in length. 

    A neck-sized case will usually be a snug fit in the chamber because only the neck dimension has been materially altered and the clearances at the base, shoulder and headspace are minimal.  Upon firing, you will often find that the bolt opens harder and with a click at the top of the opening stroke.  That is because those minimal clearances were insufficient to allow the brass to expand and spring back properly and it is now bearing firmly against the chamber walls.  If the base isn't sized enough, you'll get the click as the bolt begins to cam back for primary extraction. 

    Brass that was neck-sized in this die gave a reasonably normal feel on closing but exhibited all of the tight-fit symptoms after firing.  Closing was normal due to the small amount of sizing being inadvertently done by the sliding sleeve and the gentle shoulder angle of the .30-06.  Most neck-sizing dies don't touch the body at all and even the sliding sleeve type might not contact the case in most situations; this just happened as a coincidence of my chamber and the sleeve dimensions.

    Partial Full-Length Sizing If you've been around reloading for any length of time, you've probably heard someone refer to "partial full-length sizing."  The general idea is that by slightly raising a full-length die in the press, you can use it as a neck die and avoid the other dimensional changes that accompany full-length sizing.  The proponents of this practice usually claim longer brass life as a key benefit.  This is flatly wrong, there is no fudging this point - partial full-length sizing is detrimental to your rifle!  Let's have a look at what happens to the case when a full-length die is used in a manner other than that for which it was designed.

    We took five more cases and measured as-fired (AS) and after the partial full-length sizing process.  In this case, the die was raised 0.020" from its normal position.  As you can see from the chart, the base and shoulder were reduced in diameter just as much as when the full-length die was used normally (see below).  Most importantly, the headspace dimension increased.  This is not a trivial or insignificant matter; an increase in the headspace dimension will create rifle problems.  Because the case does not spring back longitudinally when fired, the headspace dimension of the fired case is essentially equal to that of the chamber.  When you close the bolt on a case with a longer headspace dimension, you are using the chamber as a resizing die and the bolt as your press.  Not only are they not designed for such use, but the stress of closing against an interference fit will quickly wipe the bolt's locking lugs clean of any lubricant.  Pretty soon you'll start to feel the bolt close harder and harder.  By the time you stop to see what happened, there may be significant galling of the locking lugs.  Now you have a big gunsmithing bill ahead; the lugs and lug seats will need to be recut, the barrel set back and perhaps the bolt re-timed.  And guess what?  Since the brass went through all of the full-length sizing dimensional changes, what did you gain?  Nothing, not one darn thing.  You lost quite a bit, however, on the rifle repair and I guarantee that the hard bolt closing didn't help your score one bit either!

    Full Length Sizing  Now let's examine full-length sizing.  If you're a Highpower shooter, this is really the best option; for other forms of shooting it probably is also, but I don't like to comment on disciplines in which I don't participate.  As you'll see, when the full-length die is properly adjusted, you'll reduce the base, reduce the shoulder, reduce the headspace by 0.001" to 0.002", reduce the neck diameter (not shown) and the length will increase and will need to be trimmed.  This is the real life cycle of brass and eventually, after a fair number of resizing operations, the brass will fail, either through case head separation, neck splits, or other forms of failure.  Depending on the exact form of failure and the number of cycles the case lived through, you may need to examine your practices  Ten firings from a bolt action is not unreasonable; more than that is a nice bonus, less is cause for investigation.

    Moving Metal
    The cartridge case is a tapered cylinder right up to the shoulder.  When you squeeze that cylinder down in a resizing die, it will flow forward; both the base to cone (headspace) and the overall length will grow.  When the case shoulder contacts the die's shoulder, it will be pushed back to the proper dimension.  But with either neck sizing or partial full-length sizing, the shoulder never makes contact and we're left with an excessively long headspace dimension.

    Proper adjustment of the full-length die will keep all dimensions within the tolerances and clearances needed for proper operation of the rifle - including maximum accuracy.  Accuracy comes from consistency, and only a full-length sized case is consistently like its mates.  Neck sized cases will  over the course of two or three firings; not only becoming quite tight in the chamber, but will do so to varying degrees, leading to inconsistent bolt operation and inconsistent barrel harmonics.  A fired case hits the inside of the chamber hard enough to initiate an element of the barrel's vibration pattern; do that inconsistently and your accuracy will suffer.  Partial full-length sizing is bad in every aspect and the only remaining thing I have to say about it is that had I used a more aggressive die, such as the Hornady, the headspace growth would have been significantly greater. 

    Highpower shooters need reliable accuracy; it's easy to lose sight of that when someone offers us a new reloading "trick".  I've seen way too many good, even great, shooters withdraw from a match due to problems created at the reloading bench.  Inadequate resizing is a frequent contributor to these problems, which include, among other things: galled lugs, bullets stuck in the rifling, blown out primers, split cases, excessive pressure and more.  Make sure that you don't beat yourself out of a good score before you even arrive at the range - reload carefully and conservatively and learn why things work a certain way, the rewards will be found right on your score card.

    Thanks to Jason Christ for the good looking charts!

    Related Article:

    Update: Heavy Bullets in the 1:13" Twist .30-06



    I've updated the article with more results at 500 yards - Berger 155 VLD, Sierra 180 SMK and Western 197.  Click here http://riflemansjournal.blogspot.com/2010/06/ballistics-heavy-bullets-in-113-twist.html  and the new item is towards the end of the article.

    Ballistics: Heavy Bullets in the 1:13" Twist .30-06

    Take It To the Limit: Heavy Bullets in the 1:13" Twist .30-06
    by: Germán A. Salazar


    How heavy of a bullet can you shoot in a .30-06 with a 1:13" twist barrel?  Can you shoot a 175?  How about a 185, a 190 or even a 200 grain bullet?  What's the limit?  I've been wondering about that for a while because I have just such a rifle (click here for related article).  Although the 155 gr. bullets shoot extremely well in this barrel, I like an interesting project and with a good assortment of bullet weights on hand, exploring the limits of stability promised  to be a fun and educational endeavor.

    The conventional wisdom among competitive shooters holds that the 1:13" twist barrel is well suited to shooting the 155 gr. bullets and little else - or is it?  Some years ago at a 300 Meter ISU match at Fort Benning, Tom Tamas, then the best 300 Meter shooter in the U.S., was shooting next to me with his .30-06 free rifle; naturally we began to talk about it, especially about loads.  Tamas told me that his rifle had a 1:14" twist barrel and he was shooting the Sierra 190 at a very low MV, around 2300 fps.  This is about the MV level of the famed Frankford Arsenal International Match ammo of the 1920's and 1930's, but that FA match ammo used the 173 gr. government match bullet and was fired in 1:10" twist barrels.  Interestingly, Tamas also mentioned that his rifle and load combination didn't shoot very well at all beyond 300 meters.  The successful use of the 190 at a low MV and with a slow rate of twist really caught my attention as it was not something that should work based on most shooters' understanding of external ballistics.  Yet, notwithstanding conventional wisdom to the contrary, here was Tamas soundly dominating the match with this improbable combination.


    My objective with this test is to determine how heavy a bullet will reliably stabilize in the 1:13" barrel on this rifle.  This isn't simply a theoretical exercise, but a practical one to learn about bullet stability for Highpower competition.  I'm confident that the 175 gr. bullets will work, but from there on, I don't know.  I will test 175, 180, 185, 190, 197 and 200 grain bullets from a variety of manufacturers.  Because stability is related more to a bullet's length than to its weight, I've measured a selection of useful bullets for this test and obtained the following results:

    The first length column shows the average of five samples of the actual bullets I shot.  The second length column and the G7 ballistic coefficient are taken from Bryan Litz's book Applied Ballistics for Long Range Shooting.  My measured lengths correlated well with Litz's measurements.  Litz defines projectile stability as "the ability of a projectile to maintain its point-forward orientation in flight, and return to that orientation if disturbed" (Litz, at p. 147).  That is what we'll try to evaluate with these tests.  I highly recommend a close reading of Chapter 10 of this book, it covers gyroscopic stability (Sg) and dynamic stability is detail but without overwhelming the reader with mathematics.  The concepts presented by Litz will be summarized here as they form the basis for our understanding of the test results.


    Click table to enlarge.
    The last column in the chart show each bullet's calculated gyroscopic stability factor (Sg), which is a measure of the spinning bullet's ability to resist the aerodynamic force on its nose that tries to make it tumble.  The faster the bullet spins, the greater the gyroscopic stability will be.  Gyroscopic stability can be quantified (a program for that purpose is included with the book) with Sg 1.0 being a bare minimum if a bullet is to avoid tumbling right out of the barrel and Sg 1.4 being recommended as a practical minimum to ensure adequate gyroscopic stability. 

    If a bullet has an adequate Sg, which Litz defines as being no less than Sg 1.4, then gyroscopic stability will increase as it travels downrange because the force acting on the nose decreases with velocity but the rate of rotation which counters that force stays almost the same.  Therefore the rotation's countering force to the aerodynamic force is proportionally greater downrange.  Increasing the MV of a bullet will only slightly increase gyroscopic stability because the aerodynamic force trying to overturn the bullet increases in almost perfect proportion to the increased spin rate's ability to counter it. Accordingly, MV plays a very small role in gyroscopic stability.

    If a bullet's Sg is between 1.0 and 1.4, the bullet should be stable enough not to tumble, but it won't necessarily settle into a stable flight.  This marginal level of gyroscopic stability means that the initial pitch and yaw motion that every bullet has won't damp out; consequently, the bullet will have a lower effective BC because of the higher drag induced by the pitching and yawing motions and accuracy will be compromised.  These problems will increase as the bullet travels downrange, so unlike the bullet with adequate gyroscopic stability (Sg at least 1.4) which gets more stable, the marginally stabilized bullet will become less stable as it travels downrange.

    The Sg is most easily increased for a given bullet by speeding up the barrel's twist rate.  As an example, to increase the 190 Sierra's Sg from 1.39 to 1.50, all we have to do is change the twist rate from 1:13" to 1:12.5".  However, if we were to try to do it by increasing MV, we would have to raise it from the usual 2800 fps to 3500 fps - not an easy task and certainly not possible with the .30-06.  Increased MV is not the best way to find stability.

    The other element of ballistic stability, known as dynamic stability, deals principally with the effect on a bullet of going into the transonic/subsonic region and is principally a factor of bullet design.  Most long range shooters are aware of this and load their ammunition to a sufficiently high MV to avoid this problem and it is not relevant to this test.  We are focusing on gyroscopic stability because that is exactly what is affected by the barrel's rate of twist and it is not as widely understood. 

    Moving on to the testing, there were some decisions to be made as to bullets and loads.  Because I've already shot both of the Berger 155 gr. bullets through this rifle at 500 yards, and I know they shoot very well, I didn't include them or the Sierra 155 in this test.  There was no reason to, really, because the object is to see how heavier bullets perform in the 1:13" twist; that the 155's will perform well is no mystery.

    For the sake of simplicity, I decided to use the same charge of IMR 4350 for all bullet weights.  This was a relatively light charge, about 2 grains below what I normally shoot with a 200 gr. bullet and 4 grains below my load for the 175.  No effort was made to tune the load or seating depth to any particular bullet because this isn't an accuracy test, it's a stability test.  The Wilson seating die was adjusted for each bullet, but only to maintain a uniform 0.010" jump to the lands for all of them, not to tune any bullet to an optimum level.  The goal was simply to see at what bullet weight we would fall below a minimum practical level of gyroscopic stability.

    Saturday morning rolled around right on schedule and I met some fellow members of the Desert Sharpshooters Rifle Club at the Ben Avery range for our regular practice, chrono and test session on the 100 yard range.  After setting up the reloading equipment and firing a few shots to confirm the zero, we got down to the business at hand.  Temperature in the low 90's, humidity 10%, a moderate strength, variable wind from the left and bright sun were the prevailing conditions.  For those who want to do some math later, the range is at approximately 1640 ft. elevation.  All firing was done prone, with iron sights, at 100 yards on the NRA 100 yd. Smallbore target (A25) which has a 2 inch 10 ring and a 1 inch X ring.







    First up was the 175 gr. Berger match boat-tail bullet (Sg 1.52).  As I fired, the wind kept pushing my shots to the right.  I made several small adjustments, but generally the group formed up at about 5:00 in the 10 ring with a couple to the left of that during some let-offs in the wind speed.  The load seemed very mild, primer edges well radiused, no stickiness on extraction.  I wasn't too surprised that they all went in point-first with no signs of instability; I didn't think the load was particularly accurate, but it was also very light, so I won't judge the bullet's potential by that.  I shoot the 175 Berger in my Palma rifle quite a bit and know it to be an excellent bullet when it has the right load behind it.

    Next in line was the Sierra 180 Matchking (Sg 1.49).  The 180 is only slightly longer than the Berger 175, and given the results from the 175, I had no reason to think the 180 would not be stable.  That turned out to be a good assumption, with the 180's forming up nicely in the middle of the target.  The group strung vertically, but again, it was a very light load and that is a common characteristic of light loads.  Vertical dispersion was about the same as the 175 Berger, and all bullets went in point-first with no elongated holes or other signs of impending instability.



    Continuing up the weight scale, I next loaded the 185 gr. Lapua D46 (Sg 1.44), a FMJ mach bullet designed in the 1930's and still a darn good choice.  Not as sleek as many modern designs, the 0.309" diameter D46 has a way of performing well in all sorts of barrels - but would the 1:13" twist stabilize it?  As the picture shows, the D46 shot better than the previous two bullets.  In part we can attribute that to the fact that the standardized load for the day was slightly closer to a normal load for the D46 than for the lighter bullets.  In any event, once more, all bullets went in point-first and cut nice round holes.


    As we moved to the Berger 185 match boat-tail (Sg 1.33) I was beginning to think we were near the end.  The 185 Berger is quite a bit longer than the D46 and the Sg was now below 1.4.  The first shot went into the X ring at 4:00, the next one made the hole slightly larger, the next two barely increased it.  I couldn't believe what I was seeing.  The next six shots stayed pretty tight and the group was excellent.  What really surprised me is that the Berger 185 was shooting better from this barrel than it has from the 1:10" twist and 1:11" twist barrels in which I've previously tested it. 


    Now we were close to Tamas' old 300 meter load with the Sierra 190 gr. Matchking (Sg 1.39) in the 1:13" twist barrel.  The wind from earlier in the day was back and I made a few corrections trying to keep the shots centered, but mostly succeeded in scattering them horizontally.  The load didn't exhibit any pressure signs (nor should it at the level I was using) and the shots followed my adjustments of the windage knob.  Other than one shot at 10:00 (which is a normal "bad shot" location for me) the 190 Sierra held great elevation, all shots went in point-first and all holes were nice and round.  I was surprised, this was not at all what I expected; perhaps I should have been more confident, after all it wasn't too different from the Tamas load that worked so well.

    Next up was the 197 Western match hollow point (Sg 1.51).  Although the 197 is heavier than the Sierra 190, it is a shorter bullet, with a fairly blunt nose, thus the Sg was back into the "safe" zone.  This bullet was originally loaded in Western match ammo in the late 1950's and early 1960's; mine are from WCC 60 .308 match ammo which I pulled down.  Because they're shorter than the 190 and because they were intended to work in a 1:12" twist, as is standard for the .308 ammo they came in, I expected good results and I got them.  The 197 Westerns wadded up nicely with 6 shots in a single hole in the X ring and the remaining 4 close by.  No surprise at this point, but it sure was satisfying and the other club members were definitely becoming more interested in the test.

    Now we reached what would be the end of this phase of testing simply because we were down to the heaviest bullet I brought: the 200 gr. Sierra Matchking (Sg 1.33).  Whether they went in point-first or not, we were out of bullets to test!  With the load being a lot closer to normal than it had been for the other bullets, the rifle took on a more characteristic bark with each shot and the bullets began to tear out the X ring at 8:00.  I was almost laughing as I looked in the spotting scope after each shot, because the hole kept getting bigger, but the bullets weren't going anywhere else!  By the time I got to the tenth shot I was trying a bit too hard and that one snuck out of the X ring, but a 100-9X was pretty darn good for a combination that the conventional wisdom would have rejected for use at any distance.  Although the Sg of 1.33 is marginal, at this short distance, the inability to damp out the pitch and yaw motions wasn't having any particularly negative effect.

    I loaded six more of the 200 gr. Sierras and headed over to Norm's chronograph as he was wrapping up his load testing.  My normal load for the 200 gr. Sierra yields 2760 fps with H4350; the light test load I was using gave 2630 fps.  I didn't chronograph any of the other loads, but since the powder charge never varied, we can safely assume that all the other bullets, which were lighter, had a higher MV than the 200, although still below their normal MV in the .30-06; probably closer to the MV one would expect from a .308.  The heaviest and slowest combination was the least likely to stabilize, but it did and it did so in grand style with that 100-9X.

    Seven different bullets, ranging in weight from 175 gr. to 200 gr., fired through a barrel with a rate of twist that we generally consider unsuitable to stabilize them and not only did they all stabilize, they seemed to shoot better as they got heavier!  You might properly conclude that I was very happy with the way the first phase of the test went.  Although the results are counter intuitive to us at first, they are consistent with Litz's theoretical work and are good evidence that a marginally stabilized bullet can shoot well at short range.  The more interesting side of the testing is the mid-range or long-range test.  The next phase would be to try some of these combinations at 500 yards to see if the stability would hold up or if  they were too marginal and would deteriorate with distance.

    Tamas' old comment about poor accuracy beyond 300 meters for his slow twist 190 load was prominent in my thoughts.  My calculations yield an Sg of 1.14 for the Tamas load, that's even more marginal than any of my loads and yet it shot well at 300 meters.  I decided to shoot at 500 yards with the 190 gr. Sierra (Sg 1.39) and the 200 gr. Sierra (Sg 1.33) because the 190 was almost exactly at Litz's recommended minimum Sg and the 200 was just below it.  Those two loads should show if Sg 1.4 is a meaningful recommendation for a minimum Sg.  I increased the powder charge by 1.0 grain to bring it closer to my normal load for those bullets in order to avoid load-related accuracy issues.  That charge increase should raise the MV by about 60 fps, so the 200 were probably in the 2690 fps range and the 190's at about 2750 fps.  This is still about 50 fps below normal, but close enough without detailed testing of this lot of powder and this barrel's preferences.  The test ammo was loaded at home, in the usual manner with all charges weighed.

    Early on Sunday morning, Mark Ahern met me at the Phoenix Rod & Gun Club for the 500 yard test.  For those who want to do some calculations, temperature was about 75 degrees, humidity 20% and elevation is about 1150 feet, so conditions were a bit less favorable for stability, but not a particularly significant amount.  The target is the NRA MR65, the 500 yard slow-fire target with a 10 inch 10 ring and a 5 inch X ring.  As always, shooting was done prone with iron sights.

    After I took a few shots to sight-in, Mark pasted a fresh target face and I fired 15 shots with the 190 gr. Sierras (Sg 1.39).  As the picture shows, they scored a 150-8X and at one point, blew the spotter out in the X ring, doing some damage to the target face.  There was briefly a slight wind to the left, but not particularly troublesome, then it stopped and the flags hung on the poles.  I was zeroed a bit low as it turns out, but I was trying to leave the elevation alone in order to gauge the load.  Overall, I would say that the 190's stabilized at the bare minimum Sg worked very well at 500 yards. 



    Mark then ran up a second target for the 200 gr. Sierras (Sg 1.33).  Again I fired a few sighters, Mark put up a fresh target face and we began.  My optimism faded quickly as it became apparent that although the bullets were going roughly into the center of the target, they just weren't doing so accurately.  Shots were off call, with a larger elevation spread than the 190's and some were going out to the sides with no wind to account for it.  The score of 146-4X wasn't very impressive, especially considering how well the 200's shot at 100 yards. 


    Mark reported that the bullet holes from the 200's were not perfectly round.  However, after having a spotting disc spindle inserted, then a paster put over the hole and later removed for the photos, that was impossible for me to see the slight elongation.  Mark is a tool and die maker with a fine eye for detail, so I have no doubt that what he said is an accurate observation and indicative that at an Sg of 1.33 the 200's losing some degree of stability and no longer at peak accuracy by 500 yards.  I finished the morning by firing a few left over 190's and 200's into a single target at 100 yards; for what it's worth, they all went into a tight group similar to the previous day's shooting at the higher elevation of the Ben Avery range.

    That the 1:13" twist just wasn't enough for peak accuracy with the 200's at 500 yards was no real surprise.  That it kept the 190's shooting well was surprising to me but in line with Litz's recommendation of Sg 1.4 as the bare minimum for good downrange stability.  When I first read the stability chapter in Litz's book, I wondered how accurately derived that recommendation of Sg 1.4 might be - was it just 1.0 plus a big safety margin or was it experimentally derived?  I don't know how Litz got there, but my testing certainly supports that figure as being a very useful guide when evaluating potential bullet and barrel twist combinations.

    UPDATE - June 5, 2010

    This target shows the 155 Berger VLD  (Sg 1.44) fired at 500 yards.  I decided to shoot one target with this bullet because it has produced scores of 200-14X and 200-17X for me at 500 yards in this rifle in recent weeks.  This time it was a 199-12X under hot and breezy conditions.  Although I think there was more vertical dispersion than usual, all my loads were acting a bit hot on this day (about 100 to 102 degrees while firing) so that may be a big part of it.  This target is a useful baseline for evaluating all the others.
    Next up was the Sierra 180 Matchking (Sg 1.49).  Like the 155, it has an Sg over 1.4, Litz's minimum recommended number and therefore should shoot well.  In fact, it did, most of the vertical dispersion you see occurred in the first few shots when the barrel was settling in to the powder change from the previous string (H4350 with the 180 from surplus 4895 with the 155).  The score was a 199-7X, not as good an X count, but shots were on call and I lost a few X's to the settling-in

    .
    The last bullets fired was the 197 gr. Western (Sg 1.51) which gave me a 197-10X.  Despite it's heavy weight, this bullet is very blunt, that's why the Sg is high and the BC is low.  Therefore, it really drifts in the wind, about the same as a 168 Sierra is my best estimate.  Accordingly, I got pushed out the sides a bit.  There was also some settling-in as I switched to H4831sc for this load.  Overall, the 10X count shows that the bullet performed well in the 1:13" twist as the high Sg indicated that it would.  Compare this to the target fired with the 200 Sierra (Sg 1.33) and you'll see what a difference a higher Sg can make.  All shots after the settling-in were on call and predictable.

    My conclusion from this test is that Litz's recommendation of a minimum Sg of 1.4 is a very sound piece of advice and if followed, will allow you to use some bullet/twist combinations that run counter to conventional wisdom, but will perform very well.  I also learned that while stability and bullet weight are closely related, bullet form has a lot to do with it also and muzzle velocity has very little to do with it.  Notice that the last three bullets fired at 500 yards each increase Sg as they increase weight!  Why?  Because they are also becoming more blunt as they go up in weight; that's just a function of the three bullets I picked, of course.  Had they all been from the same maker, that would not likely be the case.  I still prefer a 1:11" twist for my general shooting with the .30-06, but it's interesting to know what can be done with the 1:13" twist.  I set out to learn something new and I learned even more than I expected about what works, what doesn't and most importantly - why they do or don't work.

    Bryan Litz's book can be bought directly through his website http://www.appliedballisticsllc.com/ and I highly recommend it for those with an interest in external ballistics.  If you would like to use the Litz program to calculate Sg or for general drop and drift calculations but don't have the book, Bryan has generously given permission to our club to host an online version of the program at our website http://www.desertsharpshooters.com/ , just click the Ballistics Software menu item.

    My sincere thanks to Mark Ahern for his help with target pulling and photos, to Oliver Milanovic for more target pulling, to Jack Arnold who also helped with the photos and to Jason Christ who put the data chart into a useable format - thanks guys!


     

    All contents Copyright 2012 The Rifleman's Journal