September 2011 Cover Page

  September 2011
  
The Rifleman's Journal
A Collection of Articles Dealing with Rifle Accuracy Topics

Clint Dahlstrom - Canada
1962 World Championship - Cairo
300 Meter and Smallbore
(photo 2007)

This Month:
Hap Rocketto - Hap's Corner
Germán Salazar - Rifles and Reloading


15 Cents 

Equipment: The Tubegun in F-Class - Part 4

The Tubegun in F-Class - Part 4
by Germán A. Salazar



This final installment of the series is simply a confirmation that the work John performed on the rifle and our various ideas about what to do all worked well. There aren't any additional developments presented here.

As I mentioned in Part 3, today we went to the weekly 500 yard match at the Phoenix Rod & Gun Club and gave the various modifications a good test. Conditions were breezy with the temperature just under 100, so a very nice day by summer time standards in Phoenix.

The bipod clamping block worked perfectly, never moving even a millimeter. Between sighting in the rifle, firing the match and shooting a few extra rounds at the end, I fired 80 rounds of .308 with 190 gr. bullets. That was as good a test for the clamp's holding power as it needs; I'm satisfied that the moving bipod problems are now behind us.

The scope base modifications were a complete success as well. I lowered the elevation setting on the scope by 20 moa from last week's setting and it only took a few clicks to zero it in. There is now plenty of elevation travel left to go to 1000 yards, as well as enough down travel for 100 or 200 yards - although 300 yards is the shortest range at which we shoot.

Just as important, the windage zeroed very close to the center of the scope's adjustment range, just as we had hoped. This confirms that our slope calculations and John's milling work were on the money and that Gary's instructions on the windage problem as well as John's work on the rings worked out perfectly.

The change from medium height rings to the high rings was also just right. I was able to move the cheekpiece up a little and get the amount of cheek pressure that I normally use while maintaining a comfortable sight picture. The high rings are the ones we modified as described in Part 3.

There isn't much else to say without turning it into a match report, which isn't my intention, but the scores were good for the conditions: 198-8X, 198-9X, 195-4X (591-21). That was enough to win F-Class overall, but second place finisher Christine Harris (587-26) turned in a 199-11X for her last string in F-TR, so the pressure is always on around here!

I'm satisfied that the tubegun and its accessories are now properly sorted out for F-Class shooting from 300 to 1000 yards. All that remains is for the shooter to perform up to the rifle's capabilities...

Equipment: The Tubegun in F-Class - Part 3

The Tubegun in F-Class - Part 3
by Germán A. Salazar

And now, for the rest of the story...

This should have been the simple part of the project, drill a couple of holes, pin the scope base, mill a few spots for weight savings and call it a day. Nope... it didn't go that way - but on the positive side of the ledger, John really put his talents to work and we solved some problems that we hadn't even anticipated. Our thanks to Gary Eliseo who made himself available by telephone and gave us some very valuable advice. I should mention that John is the owner of a construction company and this kind of project is hobby time for him, he doesn't do machine work or gunsmithing on a commercial basis.

Adjustment Rod
The day began early for John who showed up at the shop while I was in the dentist's chair 20 miles away. By the time I made it down there, he had already made the first item on our list, a stubby and hollowed out adjustment bar for the butt assembly. John did a very nice job on the bar, he even duplicated Gary's circumferential reference lines to ease adjustment repeatability.

The back side of the bar is solid and is drilled and tapped for an attachment screw as well as drilled for a roll pin that comes through the butt plate to prevent rotation. All of this was duplicated exactly as on the original.

The new bar saved us 2.7 oz in comparison to the original. In the picture above, you can see the new bar on the butt assembly, with the original bar underneath. If we had to find more weight savings, the bar could be thinned out some more, but we're in good shape on weight for the time being.

Scope Rail Counterbore
Our attention then returned to the scope rail. When we finished yesterday, the rail had been cut with a taper to allow the scope to be adjusted for 1000 yard shooting. However, the tapering process means that the screw holes and their counterbores on which the screw heads bear were no longer vertical, but at a slight forward angle. A check of the holes showed that they were large enough that there would be no interference with the screws. The counterbores, however, had to be straightened out to allow the screw heads to seat squarely and apply clamping pressure evenly.

If life were simple, we would have simply clamped the scope base down to the mill table, and brought an end mill down to countersink the hols in a vertical plane. Life is not simple.

You'll remember that in Part 2 of this series, I mentioned that the slot for the scope rail that is cut into the tubegun sleeve is actually angled; in my rifle, it is 0.020" deeper at the front than at the rear. The scope base attachment holes are drilled on that same angle for ease of manufacturing. Therefore, we would have to account for that angle in our setup.

We shimmed the front of the scope rail the correct amount, clamped it down and then countersunk the holes just enough to clean up the screw head seat. The picture above shows the setup, the one at left shows the re-cut seat. Once all three screw holes were re-cut, we were ready - or so we thought - to pin the base to the tubegun sleeve.



Windage Alignment
Apart from the elevation issues with my Leupold scope, I also noticed that the windage was fairly far over to one side. When I spoke to Gary about this, he explained that the slot in the sleeve is cut just a little wider than the scope base to allow the user to center up the scope fairly accurately. The procedure is to install the rail with only the middle screw, and it should be a flat head screw with a tapered seat, not the regular cap head screw. Tighten it snugly, and you should be able to rotate the base a little bit. Center the windage travel on the scope, install the scope on the base, bore sight the rifle on a reasonably distant object and rotate the base to align the vertical crosshair with the object. Remove the scope carefully to avoid disturbing the rail's alignment, put the tubegun in the mill, drill the holes for the alignment pins, install the alignment pins and then the screws and you're done. That's the theory...

Weaver vs. Picatinny
I'm not a scope guy - really. The truth is, I'm a die-hard iron sight shooter forced into F-Class due to shoulder surgery. Now, I'm not saying I don't like F-Class, I do and I'm having a ball. What I'm saying is that there are subtleties that I was not previously aware of and they can bite you. The Weaver vs. Picatinny rail distinction bit us a little this morning. I'll explain the problem, hopefully it won't be too tedious.
Leupold Rings - Compatibility Problem
As I was mocking up all of the pieces, I noticed that the bottom of the Leupold QRW rings were not truly level with the scope base. This meant that the scope wasn't really centered over the base and thus would require additional windage to zero properly. Aha! Well, it's one thing to find a problem, but it's a whole different exercise to solve it.

A call to Gary led to the Weaver vs. Picatinny discussion. It seems that for all their similarities, the two systems have some significant differences. That's probably not news to any experienced scope shooter, but it was news to me. Fundamentally, the required scope rail dimensions for each are slightly different. The CSS rail is dimensioned to work with either type of ring, but is closer to the Picatinny spec. Accordingly, my Leupold rings, which are a true Weaver type, were a bit too narrow at the clamping surface to come down far enough to level out. The best solution would be to use Picatinny type rings, but we had the Weaver type and there's a match tomorrow.

We considered milling the rail to narrow it up a little, but that is actually a very big job that would have required milling all four angled surface (top, bottom, right, left). Gary suggested mounting the two rings on a 1" bar and milling the contact surface to allow the rings to come all the way down. We did just that and after a few passes of the end mill, that removed about 0.007" total, the rings were perfectly level on the rail.

The picture at left shows how the base of the ring is now level with the scope base. It's an odd picture because the camera angle needed to show the light between the ring and the rail makes the ring look narrower than the rail, but just direct your attention to the even gap - that's what we were after.

Here's another picture of the modified rings with the crossbars and clamping levers installed. By mounting the rings side by side on the bar as Gary suggested, we were able to ensure that they were both cut the same amount and on the same angle. This setup took a long time to accomplish, but it resulted in a perfect cut.

Pinning the Scope Base
After all of the unanticipated work with the scope rings, we were finally able to boresight the rifle, and rotate the base to allow the rifle to be zeroed with the windage travel reasonably close to center.

The picture at left shows the tubegun clamped into the mill vise and the drill bit following the pin hole in the scope base and into the sleeve.

There are two pin holes, one at each end. Once they were both drilled into the sleeve, we installed the pins, rechecked the scope alignment (for the 20th time it seemed) and wrapped up for the day. Here you can see the roll pins already installed and the flat head screw still holding the base down. That screw was then removed and the regular cap head screws re-installed.

Making Weight
There was, of course, one not so small item left on the agenda: weigh the rifle. The F-TR rules call for a maximum rifle and bipod weight of 8.25 kilos (18 lb. 3 oz.). We made it with nothing to spare. I might look for a few small weight trimming opportunities, but for now, the rifle is complete and legal. We'll give it a trial by fire tomorrow at the club match at 500 yards.

Success!
John says it's always a good day at the shop if you leave with the same number of fingers you came in with. We took inventory and it looks like it was a good day.

Click here for Part 4

Equipment: The Tubegun in F-Class - Part 2

The Tubegun in F-Class - Part 2
by Germán A. Salazar

John Lowther very kindly volunteered his time, skill and machinery to attack a few small concerns to optimize the CSS (Eliseo) tubegun for F-Class shooting. As I noted in the first installment, the bipod mount needs additional grip to keep from sliding forward under recoil. Additionally, the scope base needs to be tapered because in its current flat configuration, I won't be able to get enough elevation travel from my Leupold scope to go to 1000 yards. In reality, my problems aren't with the tubegun, but with the bipod base and the scope that I use with it. Nonetheless, we have to make everything work as a system and that's just what we'll do.

While we're in the shop, we'll look for a place or two to trim an ounce or two of weight; that's always useful for an F-Class rifle teetering on the edge of the permitted 8.25 kilos. My rifle, with a Krieger Heavy Palma contour barrel is right on the limit, so creating a small margin is just prudent planning.

Bipod Clamp Bar
The first item on our agenda was beefing up the bipod's attachment to keep it in place. Before I even arrived, John was already busy and had begun to make the piece we'd discussed. This is an aluminum bar to go inside the handguard which will provide a lot more clamping surface than the two small flat nuts that came with the bipod. This arrangement won't work with a conventional rail (nor is it needed) but it's just the ticket with the large, but curved, inner surface of the tubegun handguard.

John milled the sides of the bar down a bit, planning on the center fitting into the rail slot from the inside. When I arrived, he saw that the bipod base plate already had that protruding surface, so we simply decided to reverse the orientation of the new bar. Two holes were drilled and tapped for a 10-32 thread, spaced two inches apart. The photo at left shows the long piece of stock with some holes drilled and tapped and the base plate on for a trial fit.


Once everything lined up properly, the bar was cut to the length of the base plate and a piece of non-slip friction tape was applied and cut to size. This will further add to the clamping power of the new piece.












The finished bar with the original lock nuts in front for comparison. Because the bar is quite a bit thicker than the lock nuts, we used longer screws to allow for a bit more torque without fear of stripping the threads in the aluminum bar. The handguard will be sandwiched between the base plate and the bar. Between the added clamping area, more clamping power and the textured surface, I'm confident that there will be no more bipod slippage.




The picture at left shows the installed bipod base with the new bar in place.

Scope Rail Tapering
The next item to address was the scope base which could use a bit of taper to allow me to zero the Leupold scope at 1000 yards. Currently, when zeroed at 500 yards, there is approximately 19 moa of upward elevation travel remaining in the scope. For a .308, the required elevation from 500 to 1000 yards is on the order of 29 moa. Obviously, without some work, this combination won't work when our long-range season begins in November.

The remedy is simple to state, a bit more involved to execute: the scope rail needs to be tapered towards the front. This causes you to elevate the muzzle a bit more (gaining elevation) in order to get the scope back to the same point of aim. If that's not intuitively obvious, the picture above should clarify it. You can ignore the "near zero" and "far zero" references, they were just on the picture which I found on the internet and aren't pertinent to the principle.

Although the tubegun scope rail isn't tapered, the mounting surface in the tubegun sleeve is tapered, accomplishing the same objective. My sleeve has 0.020" taper, newer ones have 0.035" taper. The 0.020" taper amounts to approximately 10 moa of additional elevation over a perfectly flat mounting surface. Our plan was to add another 20 moa of taper to the rail, thus allowing a 1000 yard zero on the Leupold with plenty of room to spare. Cutting too much taper creates the possibility of being unable to zero the scope at shorter distances; however, my scope was at 33 moa elevation at 500 yards, so even taking 20 moa from that (leaving it at 13 moa at 500 yards) would leave enough to zero all the way down to 100 yards.

Some of you may be asking: "Just what is 20 moa?" A circle has 360 degrees, as we learned in school, and each degree can be further divided into 60 minutes of angle (moa). Therefore, 20 moa is 1/3 of a degree. That doesn't sound like much, but it sure has a big effect as the distances involved increase. A bit of trigonometry (which I will skip here) tells us that if we want to achieve a 20 moa slope, then the height of the scope base must change 0.005818" for every 1.00" of length. We'll round that off to 0.006" per inch, then multiply by the 6.5" length of the base contact surface, yielding a result of 0.039". That is how much lower the base needs to be at the front of the contact surface than at the rear to create a 20 moa slope.

Time to get to work! John looked at the scope base's very irregular shape and pondered how best to clamp it to the mill table. Any slippage of the piece while the mill is running could ruin it, or worse, send it flying into one of us. Although clamping the front end was simple, because no cutting would take place there as it is a cantilever over the handguard, the rear was not so simple. Clamping right down on the rear of the base was out because that would cover a portion of the surface that had to be milled.



John's solution was to make a small aluminum fork which would slide over the back of the base and allow unimpeded access to the base surface. The picture above shows the fork being milled and the picture at left shows the finished fork and how it will slip over the base. Bear in mind that when being milled, the base will be upside down, so the fork will bear against the Weaver rail portion of the base.



In the picture at left, you can see how the fork was used to clamp the base. Additionally, note that there is a feeler gauge under the very front of the rail, this was used to create the needed slope.

Although our calculation of 0.039" taper to induce the 20 moa slope was based on the 6.5" length of the base's contact surface, when it came time to clamp everything down, we realized that the best place to shim the base was right at the front. Because the total length of the base is 10", it was simple enough to calculate that the shim at the front needed to be 0.060" to maintain the 20 moa taper.

John spent about 15 minutes carefully setting up the depth of cut so that the mill would just barely cut at the back end of the base and cut the targeted 0.039" at the front of the base contact surface. The real work was in the calculations, the setup, the checking and double checking. Once everything was set, it was a matter of letting the mill run and work its way up the rail.  After the cutting was done, we measured and found that we were within 0.001" of our target number. Not bad at all, and perfectly acceptable considering the slight imprecision involved in shim placement.

A careful look at the base in comparison to the handguard will show the taper that we created. Click the photo to enlarge it if it isn't readily apparent.

So an evening's work by a skilled craftsman (I mean John, of course, all I did was get in the way and take pictures) produced solutions to two problems. In Part 3 of this series we'll look at pinning the scope base to the tube to prevent any possibility of loosening under recoil with heavy loads and a heavy scope, and we'll look for some weight saving opportunities.

Click here for Part 3

Equipment: The Tubegun in F-Class - Part 1

The Tubegun in F-Class - Part 1
by Germán A. Salazar


The tubegun has truly changed the face of Highpower shooting over the past five years or so. Specifically, the CSS (Gary Eliseo) tubeguns, which are made for a broad variety of actions and configurable to single-shot or repeater, have truly helped the sport to grow. That's not just idle talk, the two principal factors that made the tubegun so important to our growth are the ease of transition for AR15 shooters moving into a bolt-action rifle and the absolutely ridiculous length of time it currently takes to get a stock from the conventional stock makers. My last conventional stock took well over two years from order to delivery (plain fiberglass); one of my friends has now been waiting four years for a simple wood stock for a Smallbore rifle. By contrast, tubeguns, which are largely CNC machined, are delivered in a reasonably short time - weeks or a couple of months at most.

Notwithstanding the foregoing, the tubegun would never have attained its present success if it weren't for one simple fact - they are brutally accurate. I have three CSS tubeguns, two with the Borden Tubegun Special action; one chambered in .308 and two in .30-06 and they are my favorite prone rifles due to their accuracy and great ergonomics. Great accuracy, great ergonomics and honest availability - those factors are just as appealing to an F-Class competitor as to a prone shooter, and indeed, the tubegun is making solid inroads into F-Class.

When I began shooting F-TR a few months ago, however, I didn't begin with the tubegun because I didn't want to chew up what I knew was a fantastic barrel while I learned the ropes of F-Class shooting. Instead, I used an older, conventionally stocked rifle and it worked well; but I'm now ready to give the tubegun a try in F-TR.


Bag Rider on CSS Tubegun stock
 In preparation for this, Gary shipped me a rear bag rider that simply bolts on to the buttplate. Simple and light, it works very well. The bag rider can be installed with either the sloped surface or the flat surface (parallel to the bore) in contact with the bag in accordance with the shooter's preference. Because I prefer to use the rear bag for small elevation adjustments, I elected to install it with the sloped side to the bag.

Unfortunately, the scope setup didn't go quite as smoothly. I mounted my Leupold BR36 at the range right before the match and discovered that my rings were too low for comfortable viewing. After struggling with it during the first string, I temporarily solved the problem by removing the adjustment wheel. This allowed the cheekpiece to drop a little lower and I was able to get through the match with a greater degree of comfort. Obviously, the correct solution will be to use a set of high rings in place of the current medium height rings.


Bipod slid to the end of the fore end
 As the match got underway, it looked like everything would be fine with the first ten shots at 500 yards scoring 100-9X; the second ten weren't quite as spectacular and I ended with a 199-13X, dropping the point on the 19th shot. The second string was downright disappointing with a 195-9X that suffered from a lot of high and low shots. It wasn't until that string was over that I found the bipod attachment was loose and had moved forward about six inches to the end of the handguard. I felt somewhat relieved to find the source of the problem; in fact, I suspect it began to move after the first ten shots of the first string.


Before beginning the third string, I tightened the bipod support bracket; however, it loosened once again during the string with the inevitable increase in vertical dispersion resulting. Subsequent examination revealed the source of the problem: the two small plates that grasp the interior of the rail just don't have enough surface area in contact with the tubegun's curved inner rail section to provide the necessary friction to resist movement. Although this hasn't been a problem with the flat rail in my conventional stock, it is definitely a problem here. Over the next week or so, I hope to make a long, reasonably wide plate that will go inside the tube to replace the two small clamping plates; that should increase the clamping area by a factor of four or five.

The scorecard tells the whole story - a strong beginning before the plate began moving, not discovered until the end of the second string, more loosening in the third string along with increased wind dispersion. Hopefully, next time we'll at least eliminate the mechanical problems and be able to once more focus properly on the wind.

By the way, if you want to download the scorecard form, plot sheets or other club resources, they are available on our club website http://www.desertsharpshooters.com/

F-Open competitor Chuck Gooding with his Clark Fay built 6BR Panda. Chuck is tough competition and keeps me trying hard just to get close to his scores. Clark also does the metal work on my rifles.

Click here for Part 2



Hap's Corner: A Chapter of Accidents

A Chapter of Accidents
by Hap Rocketto

As the supervisor of a high school academic department, which includes both chemical labs and art supplies, I find safety an issue that is always in the back of my mind. In the 18 years since my school opened my department has had only a few minor cuts and burns to report. They inevitably occur during one short lab when we teach the kids how to cut and bend glass tubing. Hot glass looks no different than cold glass and glass is brittle so when you mix those conditions with 14 year olds inevitably some skin will be scorched and some blood will flow.

In the many safety bulletins that I read I note that shooting rarely, if ever, shows up on accident lists. It should come as no surprise that this is the case because legitimate firearms owners are well aware of the inherent possibility of accidents with guns and respond accordingly with great responsibility. The shooting sports are very safe. However, I am reminded of some unusual injuries at ranges.

In the 1960s my brother Steve ran the rifle range at Camp Wakenah, the local Boy Scout Councils’ summer camp. I succeeded him in that post when he moved up to, if you can believe it, the position of waterfront director. There he was in charge of a half of a dozen well-muscled bronzed young men who taught swimming and boating. He was even bronzed himself, but that is another story. It turns out that in the five years that we ran the range it incurred the second highest accident rate at the camp.

We never had a shooting accident, however, while the youngsters were waiting to shoot they whiled away the time working on handicraft projects. Many of them had recently bought razor sharp whittling knives and neckerchief slide kits at the camp trading post. While they waited they took out the knives and furiously flailed away at white pine, yellow poplar, and their fingers. Our ready line accounted for dozens of stitches each summer.

The most dangerous area was the handicraft lodge itself. There the boys sat hacking and hewing at lumber and limbs from morn ’till night. The wooden floor was a rust brown color from many years of soaking up scout’s blood. The floor was always covered with wood chips, saw dust, and blood easily reminding one of a butcher shop. Perhaps the only other area that could match it was the scaffold in The Place De La Revolution upon which the guillotine stood during France’s Reign of Terror. Fed by tumbrels full of aristocrats, instead of Boy Scouts, the French abattoir barely outdistanced the handicraft lodge in bloodshed.

In the early 1980s Mark Lasrich and my brother Steve traveled the summer shooting circuit together. When this Laurel and Hardy team ended up at Perry, in 1983, the accident rate soared. About two days into the NRA Championships Lasrich’s glasses fogged up during a rapid sitting string and he tore off his glasses to shoot the last shot. The averages of having a punctured primer are astronomical. Lasrich beat those odds and was rushed to Magruder Hospital. The damage was slight but he had to wear an eye patch for the rest of the week forcing him to withdraw from the rest of the tournament.

The next day, Steve, who is a brilliant theoretical and practical physics teacher, decided to leap off of one of the shooters’ trolleys that were provided to move competitors and equipment around the ranges. A quick calculation, based on the estimated speed of the vehicle, momentum, acceleration of gravity, and mass, informed him of the speed that he would need to avoid falling. He started pumping his legs and leaped from the cart forgetting that his mind is much more athletic that his body. Released from the Magruder emergency room with his left elbow in a bandage and his shooting at Perry finished he joined Lasrich on the disabled list. The two stalwarts did not let the rest of the week go to waste. They spent the few days remaining exploring all of those obscure places at Perry that we wish we could visit but never have the time.

Everyone in the free world witnessed me being shot between the eyes during the Wimbledon Cup Match in 1976 (ricochet in the pits), but few people either saw, or heard of, this little incident that involved my brother few years later. Steve was sitting on the bench next to the phone after scoring a Leg Day rapid-fire string at Perry. A strong wind was blowing and it dislodged the scoreboard on the target to his left. The scoreboard flew across his point and struck a member of the pit crew to his right a sharp blow to the head. The target puller dropped like a pole-axed ox as blood began to gush from his head like Spindletop.

As Steve turned to help he yelled to the man next to him, ” Get on the phone! Call for the camp doctor!”

“I am the camp doctor!” came the reply.

Surprised, Steve turned in his tracks and asked, “What are you doing here?”

The sawbones shot back the obvious reply, “It’s Leg Day, isn’t it?”

As a result of good training and responsibility there are precious few shooting injuries. Most are generally shooting related injuries, but Leg Day is always Leg Day.

 

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