August 2011 Cover Page

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

Bob Jensen - 1977 Wimbledon Cup Winner 200-10X


This Month:
Hap Rocketto - Hap's Corner
Dave Whitford - .300 BLK AR15
Germán Salazar - Rifles and Reloading


15 Cents 

Reloading: Pressure By Any Other Name...

Our old friend Lee writes this month with some fairly common problems. I though that posting the questions and answers here might be useful to many other reloaders who are getting past the basic level and beginning to experiment and develop their loads a bit more. - GAS -

Pressure By Any Other Name (is still pressure)
by Germán A. Salazar




Hello Germán,

Glad to hear the shoulder is progressing.

I have recently come upon what I would call my first "reloading issue", this is the background I can provide.

I was trying out some 168 gr. Sierra Match Kings with twice-fired, neck-sized only Nosler brass. I started with 55.0 gr. of H4350 seated with a 0.020" jump, working my way up on the powder charge (checking the primer after each shot for trouble signs) in 0.5 gr increments up to 57.0 gr. of H4350. At that point, problems surfaced.

The first shot at 57.0 gr. required higher than normal force to rotate the bolt after the shot. I checked the primer and it was not even flattened. The second shot at 57.0 gr. was even more difficult to extract and had a slight crack in the middle of the case. I stopped and went home to investigate the problem. I thought that 57.0 gr. of H4350 should be well below max with a 168 gr. bullet, right?

I disassembled the remaining loads, all powder charges were exact, as was seating depth on all. Talked to a co-worker who is a retired military marksman and practicing gunsmith and reloader,and he said it sounded like a "headspace" issue. My load book says max case length should be 2.494" and 2.484" trimmed. I have never trimmed this brass, with it being neck sized only. I start measuring the brass and most is right at 2.484", a few a couple thousandths less, and a couple at 2.480". Could the short case deliver the sort of problem with the case cracking? If so, would a simple fix be to simply full-length size and trim to specs?

I would add that the 168 Sierra performed excellent with 56.0 gr. of H4350 and should have been around 2750 fps before I encountered the trouble.

Any advice and insight would be welcomed.

Lee


Hi Lee,

Slow but sure on the shoulder recovery. I still think it'll be a total of a year (April), but I'm fairly optimistic about that at this point.

You have a few different problems going on it seems - I'll try to break them down into small bites.

1. You worked up from 55.0 to 57.0 gr. of H4350 with a 168 Sierra. Your starting load is already fairly close to maximum so it was likely that you would run into excessive pressure along that range of charges. In fact, that's just what happened - that hard bolt opening is a very good sign of excessive pressure and should be heeded. This article about pressure signs and factors should be useful as additional background to this discussion.

2. You mentioned that the primers never looked flattened. That's not unusual, even with excessive pressure. Some primer cups are very hard, Russian  magnum (Wolf, PMC) primers and Remington primers are two examples of this, but there are others I'm sure. Primer condition can be a useful pressure indicator, but only once you establish what that particular type (or even lot) of primers looks like at known normal and known excessive pressure levels. In other words, it's a useful relative measure, but not a very good absolute measure. In this case, it was the tight bolt opening that was telling the tale of excessive pressure while the primers weren't too useful. The primers in this picture (Wolf Magnum) were fired with a near maximum load but retain a full edge radius - sometimes the primer just doesn't say much.

3. You were only neck sizing - this is also going to cause the bolt lift to tighten up. When you only neck size, you don't give the case room to expand within the chamber. However, with 55,000 psi inside, the case will expand, no matter what. Therefore, what happens is that the case and barrel expand together and the barrel, which is springier, returns to its original dimension while the brass tries to stay at a slightly larger dimension - thus, the barrel traps the brass and there's your hard bolt opening. The brass needs room to expand and slightly spring back both longitudinally and radially, full-length sizing is the only way to accomplish this. Here is a good article about the effects of sizing on case dimensions,

4. Your co-worker mentioned headspace in relation to the case split, but what you measured was case length - they are not the same thing. Your measuring of case length is useful and a necessary safety measure, but doesn't address issues of excessive headspace. Headspace, colloquially, is the difference between the distance from bolt face to the middle of the chamber shoulder compared to the distance from the case base to the middle of the case shoulder. On a properly resized case, that would be in the range of 0.002". The best way to determine that is by use of a case gauge such as the Wilson. This article on measuring the case will show a few useful techniques. This article about headspace will give you more detailed information about that dimension.

5. You didn't mention if the case split was lengthwise or around the circumference. Tell me a bit more, or send me a picture and we'll talk about it.

Germán


Germán,

Thanks for the insight, I do still have so much to learn.

My load data book did not list H4350 for use with 168 gr. Sierra and I wrongfully substituted (obviously now) data from other projectile makers of the same weight. Hornady says 58.9 gr. of H4350 is max, and Speer says 60.0 gr. of H4350 is max - both for their respective 168 gr. hollow point boat tail match bullets, so I figured I was safe.

Now, after the fact I have done more data reading,and I notice that in all weights where Sierra Match King bullets do show a listing for use with H4350, that the max load is a couple grains less then with other makers bullets of the same weight and basic type (i.e. hpbt). Why is this? Is there something special about Sierra's Match King line? And like I said, my load book does not show H4350 being used with the 168 gr. Sierra. The book I am using is "The Complete Reloading Manual for the .30-06 Springfield". It covers Accurate, Alliant, Hodgdon, Hornady, IMR, Lyman, Nosler, RCBS, Scot, Sierra, Speer, Winchester, etc. - 155 different bullets and 81 different powders. If you want more specifics, just ask, I appreciate the help.

I threw out the case that was difficult to extract, and the one which actually cracked (to ensure they weren't loaded again) so I cant provide pics, but the one that cracked did so around the body at about mid-case, not lengthwise. I also was using a CCI BR-2 primers for the first time, supposedly they are hand assembled and as good as you can get in a reasonably priced primer.
On another matter,who in your eyes makes the best brass in the moderate price range, Remington, Winchester...???

Thanks for the help,

Lee

Lee,
 
You wrote that the case split was circumferential, here is an article on case head separations that should be useful. Generally, they are caused by metal fatigue from excessive resizing and subsequent stretching on firing. This can result from proper sizing after a large number of firings (about 8 to 10 in a .30-06) or from excessive resizing (shoulder set back over 0.003") for a smaller number of resizings. Given that your cases were only sized twice, and only neck sized, it's possible that your chamber is a bit longer than standard and the cases stretched out on the first firing. Once they do that, their remaining life is short.
 
As was detailed in the pressure factors article that I linked above, one of the biggest contributors to increased pressure is an increase in the bearing surface of the bullet. If two bullets weigh the same, but one has a blunter shape (and thus a longer bearing surface), that bullet will generate higher pressures with the same load. Other factors include: true diameter, jacket hardness and even core hardness. That's why it's important to work up a load carefully when switching components, even if they are similar.
 
As an example, the Hornady 168 gr. AMAX has a bearing surface of 0.472", the Berger 168 gr. VLD has a bearing surface of 0.417", the Lapua 167 gr. Scenar has a bearing surface of 0.388", the Sierra 168 gr. has a bearing surface of 0.370" and the Nosler Custom Competition 168 gr. has a bearing surface of 0.346" (data from Bryan Litz's book Applied Ballistics for Long Range Shooting).
 
As you can see, the bearing surface of each of these bullets is quite different and despite their nearly identical weight, they will have very different pressure characteristics.
 
The CCI BR2 primers are very good and they do have a fairly hard cup, so the lack of primer flattening you witnessed is not surprising. I don't see any need to change from them, they are good primers and will serve you well.
 
As for moderately priced brass, I generally have a preference for Winchester, but in .30-06 I've used all of the major US made brands (Winchester, Remington, Federal, Lake City) as well as Lapua and Norma and have had good results with all of them. If I was standing in a store with some cash in my hand, I'd buy Winchester or Lapua, but if I had one of the other brands already on my reloading bench, I wouldn't hesitate to use it.
 
Finally, remember as the years go by to keep your reloading manuals up to date. Components, especially powder, change over the years and the manufacturers release new data. I have a lot of old manuals, but the load data in them is strictly there for historical reference and should never be relied upon.
 
Stay safe and have fun!
 
Germán
 

Reloading: .308 F-Class Load Development from Australia

.308 F-Class Load Development from Australia
by Germán A. Salazar

Good Morning Germán,

Hope your recovery is progressing nicely Really liked your article on shooting F Class – not just because that’s what I do, but I was interested in the Sling Aperture Shooter / F Class swap thing.

I have just got a new 30” 5R 1:12" twist Kreiger for my Barnard that I shoot F Class in Australia. I use 155 gr. HBC projectiles, an Australian made VLD that really is the standard for .308 target shooting over here.

After 20 shots running my barrel in, I did a ladder test at 414 yards - that’s as far as I can shoot at home.   You should be able to read the powder weights and velocities off the target photo. I used Lapua brass that as far as I could tell were identical weights, neck thicknesses, etc  with ADI 2208 (Varget), CCI 450 primers and 0.008" jump off the lands.

You would reckon that 46.5 gr. would be the load to try. Some thing was going on at 45.6 - 46.0 but I don’t think you would call it a node. Conventional .308 shooting wisdom in Australia is that 46 gr., or 2950-2975 fps,  is the load to use. Perhaps vary the jump a bit to get a good SD, and then turn the barrel tuner until you get the group you want.

I thought I’d share this with you and get your thoughts.  

Regards,

John








John,

Thanks for writing, the shoulder is coming along slowly, and the F-TR shooting is definitely keeping my competitive urges satisfied. In the past two weeks, I had my lowest score (566-13) and my highest score (597-32) both on the same 500 yard range! Our conditions here in the desert of the Western U.S. can be highly variable, as I know they can also be in your part of the world.

I've only seen a handful of the HBC bullets here because there is no importer, but by all reports, they are the equal of the U.S. made match bullets. You have a great looking range there, the ability to shoot and develop loads close to the reloading bench is really valuable and it looks as though you're making the most of it.  Creighton Audette's load development method is a useful tool and your target is a perfect example of it.

I agree with you that the sweet spot on your target is in the 46.5 gr. range. I'll assume that pressure signs were within the acceptable range. When I last used Varget with 155 gr. bullets, my load was right in that range also. However, I hesitate to recommend that as a universal thing because case capacity, primers, throat length and the barrel itself can have a significant effect on chamber pressure. It takes a careful workup such as yours, with an eye on the pressure signs, to be sure that the load is not only accurate, but also safe.

You mentioned that shooters in your area recommend a specific velocity range for accuracy with that weight of bullet. I hear that same sort of thing here as well, even from the highest level of the sport. Unfortunately, that really isn't a recomendation of universal applicability because rifles are just too different from one another for any such thing to be true - much though we might wish it were.

Individual testing, such as you've done, is the key to maximizing each rifle's performance. A good example is the load I used for the 597-32X yesterday; that load features a Sierra 190 at a relatively sedate 2600 fps. Despite the seemingly low velocity, pressure testing has shown this particular load to be close to SAAMI maximum allowable pressure for the .308; it's all a matter of powder selection. Although this load would be a poor choice for 1000 yards, it's an absolute hammer at 500 or 600 yards. Each competitor needs to put in the work, as you have, to find out what his rifle shoots best. There's no substitute for range time.

By the way, there might be something wrong with your camera, I noticed that both your truck's steering wheel and your rifle's bolt handle appear to be on the right side when we all know that they both belong on the left!

Germán


Hap's Corner: In Second Place I am Second to None...

In Second Place I am Second to None...
By Hap Rocketto

I have just arrived home after shooting the Connecticut Gallery Championship, a match I first shot as a high school freshman in 1962. Way back then The Gallery Match was the largest indoor match known to man. On two consecutive weekends sub-juniors, juniors and seniors fired some 3,000 sets of targets. Teams would come from all over the northeast to New Haven. The three ranges at the Old Winchester plant would be humming; kids would troop through the Winchester Firearms Museum, now located at The Cody Museum, and feast on the hot dogs and hamburgers in the Winchester Cafeteria. The high light for the youngsters would be the awarding of the Lyman Merit Medal to any kid who shot a 100 points or better. Each year you hoped to earn a bar that showed a higher percentage than the last. For many of us it was the first shooting award we would earn in match competition.

For those unfamiliar with this event, it is 20 shots for record, in four positions, in 25 minutes for juniors and adults and 20 shots prone for subbies. For many riflemen it is the most intimidating event of the year because the course of fire is so short that, while a good shooter has a good chance of winning, it is a crapshoot and any dark horse can, and has won. It takes a minimum score of 198 to be in the running and usually a 199 wins. There have been some possibles shot, the first and most of them by Freddy Cole. I have finished second four times in this match, twice with 199s and twice with 198s. There are those who feel that my karma at this match is just not good.

I opened well. I had five neat center shots that certainly would plug as “of higher value.” My first shot for record sitting was a pinwheel; I then tossed a wide nine at eleven o’clock. After gasping in amazement I settled myself, returned to the sighter and shot a ten, went back to record and shot another nine! I shrugged my shoulders, shot another ten in the sighter and finished with two more tens to record a 48 sitting.

My ego now began to exert itself. I still had a chance to win if I could go clean in kneeling and standing. As is my custom I had not “hawked” the board before the match and had no idea what was the tall score at the moment. I did know that a 198 just might do it. Shooting ten more tens was possible but it would require just a little extra effort. I just had to bear down and not, in the words of my shooting mentor Dick Scheller, “put on the collar”.

Now, you have to understand that I dogmatically believe that there is nothing that stops you from shooting tens but yourself. Each shot is an individual match and the previous shot and the next shot have no effect on the current shot. All shots are mutually exclusive. Being two down in a match that I still had a chance to win was a great challenge, but not insurmountable.

With the time zipping by I set up for kneeling, shot two center tens in the sighter and went for record. In less than 120 seconds, I was getting ready for standing and I was still down just two points. As a set up my gear for standing I checked the clock and noted that I had ten minutes left for five shots. Plenty of time and I still was not feeling much pressure. Actually my confidence was rising. Two sighters off hand were solid tens and I ventured into the record bulls. My scope dot was drifting lazily around inside the nine ring, which was good. I use a ¾ minute dot in my position scope. This means that if the dot is inside the nine ring, on the “bucket bull”, when the shot goes off it will be a ten.

It goes without saying that my hold stayed steady and I slowly approached my goal one ten at a time. While I had no pinwheels in standing each bullet hole would be considered a center shot. Finishing with three minutes on the clock I smiled to myself, content with finish. Mentally I patted myself on the back for holding together but I also prepared myself for the ragging I would receive from my teammates, and onlookers, for losing two points in such an easy position as sitting. I was, deservedly so, going to be an easy mark for the kibitzers.

After I reeled in my target, I packed my gear and walked to the scoreboard. Debbie Lyman had shot a 199 and, although I managed to save face with a 198, I was not going to win. However, all the rest of the 198s on the board had dropped their points in kneeling and standing. Because of the tie breaking rules it was going to be impossible for anyone to push me out of what is fast becoming my traditional second place finish. They would have to be more inept and unlucky than I and I had a lock on that class and category at this match.

I just don’t know why I can’t do better at this match. After all, it is only 20 shots on the bucket bull. Over time I have become philosophical about my second place record. Philosophically speaking I think what had happened to me is, in reality, a tragic cosmic traffic accident: my karma had run over my dogma.

Cartridges: 300 BLK for Over the Course

I am ocassionally reminded that not everyone shares my appreciation for the .30-06 as the true "do it all" cartridge. Some years ago, our old friend from Virginia, Dave Whitford, became one of those lost souls who succumbed to the siren song of the AR15 and its promise of high scores with low recoil - more's the pity, for Dave was a true .30 caliber man. However, there is hope; in this article Dave tells us of his recent work with a new .30 caliber cartridge for the AR15 and its applicability to Highpower competition. It would appear from Dave's effort and experience that the 300 BLK is not just for the Carlos Hathcock pretenders, but might, in fact, find a useful purpose among competitive shooters. Well done, Dave!  -GAS-

300 BLK for Over the Course
by Dave Whitford

The 300 AAC Blackout cartridge became SAAMI standard in January 2011. I infer from Internet info that this was mostly because of Remington’s involvement and push.

AAC stands for Advanced Armament Corporation in Georgia, the cartridge’s developer. AAC is under the same conglomerate umbrella as Remington, Bushmaster, DPMS, and several others, which explains why Remington pushed for SAAMI approval. AAC makes rifles and carbines, Remington produces ammo, Forster makes die sets, and Pacific Precision makes the reamers. As an addicted wildcatter, I loved this availability of no-trouble SAAMI-spec reamers and dies when I adopted my 300 BLK project in February 2011.


(L) 300 BLK with 125 gr. Speer, (C) .223 Remington, (R) 300 BLK with 155 gr. Hornady 

The cartridge, like the .30 US Carbine round, is a pistol cartridge in a short-rifle. It’s a non-proprietary update of JDK's proprietary 300 Whisper from the late 1980s, early 1990s. Apparently Remington and AAC tweaked chamber specs or cartridge dimensions slightly so as not to infringe on JDK's proprietary claim. 

However, despite the small changes, the new AAC cartridge is the ballistic equivalent of the .300 Whisper and its wildcat .300-221 Fireball spinoffs. Like the 7.62x39 Russian, it boasts .30-30 ballistic equivalency, although more efficiently with less gunpowder. More power than the .30 US Carbine comes from cut-down .223 brass that is 0.020″ bigger in diameter and about 0.040″ longer.

 My interest arose from NRA’s arbitrarily unfair scoring rule passed about ten years ago. When I began Highpower shooting in 1991, most of us shot .30 caliber rifles. The rule then was that if your .30 caliber bullet hole broke the target’s 9-line, for example, you got a 9 for score.

In the middle to late 1990s, good new .22 caliber bullets and faster-twist barrels made AR15s competitive over the course out to 600 yards. Because the ARs don’t kick much, they reduce fatigue and give a rapid-fire advantage. The .30 caliber scoring rule applied for the sub-caliber bullets: if a bullet hole was in question whether it would break the next-higher scoring line, the scorer inserted the NRA .30 caliber plug to determine the outcome.


The AR successes apparently annoyed the die-hard .30 caliber NRA fathers. Viewing the AR shooters as cheaters who used less-than-manly rifles, they passed a punitive rule that said, “If your bullet hole doesn’t break the line, you get the lower score. Period!”

A re-vote after a year’s discussion resulted in the same unfair outcome, probably voted on by the same cadre who passed the initial bad rule. What’s unfair is that the center of a .22 caliber hole is the same distance from the center of the target as the center of a .30 caliber hole made by the fatter bullet on the same path. So a .22 (or any sub-caliber) hole should score the same as a .30 caliber bullet hole, as was the case under the old rule. Recoil, or the lack of it, should be irrelevant. Sports and their technologies evolve. Reactionary rules changes should not penalize evolving technology and increasing proficiency.

This rule change annoyed me since day one. I shoot several local short-range reduced-course competitions at 100 and 200 yards so that I can shoot as many weekends year ‘round as possible. Like any shooter, I lose points when my bullet holes miss the center. I especially loathe the points lost to skinny-bullet squeakers that close in on but fail to break a scoring ring. Being annoyed about this for numerous years, I’ve been shopping for a cheap, low-recoiling .30 caliber AR to shoot. The 7.62x39 Russian was out due to its funny magazines, bad feeding reputation, and new-bolt requirement.

Three-plus years ago I became too old, slow, and deliberate, to score well in sitting rapid-fire with my beloved bolt guns and switched entirely to AR-15s. My first was a 6BR crafted by Eric Bellows. Eric also produces these in 6BRX, 6.5BR, 7BR, and 30BR and became my AR mentor.

When I reviewed the new 300 Blackout info in January, 2011, I thought I’d struck gold. After working through some development glitches, I still think so. Here was a ready-to-go AR15 cartridge that required no new bolt or magazines, but would make .30 caliber bullet holes in 100-yard targets.


Larry Racine at the lathe.

I contracted with Eric’s uncle, Larry Racine in New Hampshire (LPRGunSmith.com) to chamber and fit the barrel and I had Pacific Tool & Gauge send him the new reamer. Larry has a hoard of hammer-forged .30 caliber barrel blanks that were originally destined to be replacements on M1A rifles. Their manufacture was overseen by Creighton Audette in the 1980s, and their bores are like mirrors. When Larry was finished with his work, the barrel blank had become a heavy, twenty-inch, chrome-moly, 1 in12″ twist AR15 barrel.

AAC’s Robert Silvers was generous with his advice for my project. He’s apparently the company’s chief promoter and developer of 300 BLK ARs; most of which are suppressed, short-barreled M4 carbines for law enforcement and “black-ops” organizations. AAC also provides a 300 BLK bolt gun on a Remington Model 7 action.

Robert advised that if I were to use a 20-inch barrel, I’d need to use a carbine-length gas system. The gas port, he said, would need to be in the 0.080″ to 0.110″ range. I alerted Larry and he drilled a minimum-size gas port. Sneaking up on the final gas port one numeric drill-bit size at a time with function tests according to Eric’s prior tutelage, I arrived at 0.104″ as the appropriate gas port size for my rifle.


AR15 float tube with offhand riser and handstop before finishing.

My 6BR has a 28″ barrel. When I later got a 26″ barreled .223 upper from John Holliger’s White Oak Precision, I put a short bloop tube on it to extend the sight radius to be the same as on the 6BR; ditto for the 300 BLK, which resulted in its long, heavy bloop tube.


The carbine-length gas system meant that I’d either need to cut and alter an expensive free-float tube from White Oak or make my own. I made my own, which was cheaper if you don’t count my expensive workshop time on an interesting and fiddly project. As normal, this project began with a trip to Lowe’s to get electrical conduit, the basis for many of my rifle innovations.


AR15 float tube, finished and installed on the rifle


Top view of float tube, showing cut-out for gas block clearance.

Although Remington now makes both supersonic ammo with 125 gr. bullets and subsonic ammo with 220 grain Sierra Match Kings for the 300 BLK, component brass for handloading is scarce. Remington brass was briefly available from CMMG in Missouri, but they are presently out of stock with none expected until mid-September 2011. I shorten .223 brass just below the body-shoulder junction, de-burr it, form the new neck and shoulder through the full-length die, trim it to length, and re-anneal it. It’s not hard, just tedious.

I start with cases that weigh either 91 gr. or 92 gr., regardless of manufacture. These cases are at the low end of the weight spectrum, which goes beyond 98 gr. Weight changes in a case so small represent significant percentage differences in capacity. Although you can get cut-down and prepared brass from suppliers like CMMG, I mistrust it because I don’t know whether they began by weight sorting. I feel safer with weighed brass because of the quick-burning pistol powder and near-max recommended loadings.

Robert tested his 300 BLK on Reading’s 600-yard range one miserable Massachusetts day this spring. When he told me, I scoffed. He used a prototype 130 gr., high-BC, Sierra flat-base, which must’ve eased his plight.

Then I ran the ballistics through the Sierra Infinity program and produced some startling numbers, showing that Robert was in the correct ballpark. Although I hadn’t considered using my 300 BLK for anything farther away than 200 yards, Infinity told me that it’s also a viable 600 yard rifle, despite a rainbow trajectory. For example, the 155 gr. A-Max that works well for me, starting at 2250 feet-per-second, retains more than 1400 fps at 600 yards. Wind drift in a 10 mile-an-hour crosswind is 38″, only five inches more than a .223 80 gr. Match King starting at 2750 fps. While not ideal, the 300 BLK is a workable full-course rifle. Imagine my surprise!


.300 BLK with the Sierra 100 gr. Varminter

My two best loads have used the 125 gr. Speer TNT over 18 grains of H110 and the 155 grain Hornady A-Max over 17 gr. of H110. At 2.260″ overall length, the 155s fit the magazines better for rapid-fire. The 125s are too short for such loading, but they still feed OK.


I’d hoped to use 110 gr. Sierra Varminter to minimize recoil, but they pattern from my rifle rather than group. Recoil from even the 155s, however, is moderate because of the tiny powder charge. Shooting the rifle reveals that it’s no .223, of course, but it’s a pussycat compared with my .30 caliber rifles of yore.



I test the 300 BLK differently from any of my previous rifles, for which I used the traditional shoot-the-group-and-measure-it technique. Instead, I fire ten rounds from the magazine, and then see whether I can cover the group with a paper circle cut the same size as the MR-31 target’s 10-ring. It’s the quick way to determine whether the rifle can shoot “possibles” on the 600-reduced-for-100 target. For my present purpose, possibles are good enough. I’m not chasing half-moa groups.



I’m delighted at shooting possibles now because things didn’t begin that way. It was a gamble whether the 300 BLK would be a decent target cartridge, given its “spray-and-pray” heritage in AAC’s suppressed, full-auto M4s. In fact, early results were dismal. Both Eric and Lonnie Miller told me, “Take the upper apart and put it back together. Sometimes that’s all it takes.” Lonnie, a former armorer with the Army Rangers, also offered several juicy assembly tips.

I did as suggested, cracking the upper-receiver forging in the process because I had used blue Loctite on the barrel-nut threads during the first assembly. While awaiting a DPMS upper-receiver forging from Midway, I fixed the cracked upper forging the best I could and reassembled the upper as I do my bolt guns: anti-seize lube on the barrel-nut threads and only a modest amount of torque… far less than normally recommended for assembling ARs. The rifle shot better, not great yet, just better!

The new DPMS receiver is better in several respects. Although sold as a “stripped upper”, it’s ready to go as-is because it has no provision for port-cover hardware or the forward–assist assembly, neither of which I need or want. It also has no brass-deflector bump on the side. The deflector on the previous forging was dinging the necks of my hand-built brass upon ejection. One piece was so badly deformed that I needed to throw it away after only one firing. Finally, the DPMS upper is a little heavier-duty throughout.

These were pleasant surprises because I wasn’t aware of the differences when I ordered. Best of all, the rifle began shooting possibles right away with the new forging. My $80 mistake with the first forging really paid off in the long run.

I’ve entered the rifle in six 100-yard competitions since early May with mixed but generally improving results. The big problem was a wandering zero. I isolated that to a moving bloop tube in the most recent competition. After offhand and sitting rapid-fire, I noticed that the bloop tube had migrated almost an inch forward of the witness line I’d marked on the barrel when I first installed it, obviously from recoil. I further tightened the clamp nut and fired the 30 prone shots. The tube moved another eighth inch and might well have caused the vertical stringing on the prone slow-fire target, on which I scored only 191-4X with a pair of 8s.


Bloop Tube joint with J-B Weld

I re-installed the bloop tube at the witness line and re-zeroed it at the range. Then I slathered on green Loctite, the kind that “wicks into” a preassembled thread or joint. While the Loctite cured, I consulted Lonnie, who recommended that I also add some J-B Weld epoxy, which I did.
Now it’s test time again. I’m satisfied that the overall upper assembly – minus the bloop tube – is up to Highpower competition requirements. I’ve never before had a mobile bloop-tube on any of my boltguns or on the .223 upper, but I’ve also never before made one so long and heavy. I can always just mount my foresight on the barrel.

Far as I know, I’m the first to put the 300 BLK into Highpower competition, where it fills a good niche.


Dave Whitford's 300 BLK AR15 NRA Match Rifle





 

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