The cases are being stretched on extraction. These gas guns open up when there is a residual pressure in the barrel, typically less than 650 psia. This is to aid in the ejection of the cartridge case, but it results in stretch of the case sidewalls.
I consider Varget a bit slow for a gas gun, having tried it myself in my M1a's. I recommend you try IMR 3031 and IMR4895/H4895. I would try IMR 3031 first as it is a faster powder and the pressures at unlock should be slightly lower.
I started shooting NRA across the course service rifle just after the Garand had left the scene, but before the AR15 replaced the M1a on the firing line. Basically, once the AMU started winning the Service Rifle Championship, with their NM M16’s, which was around 1995, the AR15 disappeared quickly from the firing line. It is my recollection that 1996 was the last time the Marine Corp Rifle Team used the M14 as an across the course service rifle. In 1997 the Marines all had match M16’s. This is over 20 years ago and so the memory of the M1a as a match rifle is probably fading, and so were its peculiarities as to ammunition and case life.
At the time, experienced shooters recommended that cases would last only four or five reloads, which is about 5 to 6 firings, and to discard the cases before the case heads came off in the rifle. They would show me their cases, some I would take home, section them, see for myself how much severe case head stretch had developed. Garands and M1a’s are hard on brass:
I met a Distinguished HM who was shooting lubricated cases in his M1a. He left the RCBS case lube on his cases, never tumbled the lube off, and he said he could take a set of brass all shooting season. He was a gunsmith and a shooter who had won every XTC medal you could get, with lubricated cases, so his credibility was high. Like others I had read Hatcher’s Notebook and its warnings about greased bullets, and of course read all the gloom and doom predictions from in print gunwriters about oil/grease on cases, but here was something that was clearly working out differently from the prognostications of the authority figures.
In time I determined that the Distinguished HM was 100% correct, and the greased bullet/case fears were baseless.
Cost is an important consideration to me. There are those to whom case life and case cost are irrelevant, but few people got to retire with footlockers of free military brass. I have noticed that new “bargain” 308 Win is priced $22.00 for twenty rounds, so brass has become even more expensive over the years. While I cannot speak for others, but for me, saving money is important: the cost of replacing cases after five firings is significant, especially if you are shooting an M1a to earn the Distinguished Rifleman’s Badge . Being able to amortized the cost of a set of brass, 10 or even 20 firings, results in considerable cost savings over tossing the brass after five firings.
Brass life in a bolt rifle can be orders of magnitude higher than what a gas gunner can expect. Bolt rifles are easy on brass, less scratches and dents, and the brass is not stretched on extraction because the bolt is opened after chamber pressure is zero. The primary cause of case head separations in a bolt gun is due to excessive set back of the shoulder during resizing. Cases are really meant to stretch once, and not more than 0.006”, which is the average distance between “Go” and “No Go” on a headspace gage. If cases stretch more than that, depending on a number of variables, cases will break.
Garands and M1a’s, are much harder on brass than bolt rifles. Gas guns are very hard on brass because they unlock while there is still pressure within the barrel. Col Chin, in his Machine Gun series,
https://www.ibiblio.org/hyperwar/USN/ref/MG/index.html calls this the residual blow back effect. Unlocking while there still is pressure in the barrel pressure is deliberate, engineered into the timing of the mechanism, and adds to reliable function of the mechanism. The residual blow back effect will pop the case out of the chamber as long as barrel pressures are low, less than 650 psia, and if case to chamber friction is low. However, since the case is moving, with the insides pressurized, this also has the effect of stretching the case. Hatcher explained, in Army Ordnance Magazine, March-April 1933, how cases stretch and why lubrication is essential in retarded blow back mechanisms:
Automatic Firearms, Mechanical Principles used in the various types, by J. S. Hatcher. Chief Smalls Arms Division Washington DC.
Retarded Blow-back Mechanism………………………..
There is one queer thing, however, that is common to almost all blow-back and retarded blow-back guns, and that is that there is a tendency to rupture the cartridges unless they are lubricated. This is because the moment the explosion occurs the thin front end of the cartridge case swells up from the internal pressure and tightly grips the walls of the chamber. Cartridge cases are made with a strong solid brass head a thick wall near the rear end, but the wall tapers in thickness until the front end is quiet thin so that it will expand under pressure of the explosion and seal the chamber against the escape of gas to the rear. When the gun is fired the thin front section expands as intended and tightly grips the walls of the chamber, while the thick rear portion does not expand enough to produce serious friction. The same pressure that operates to expand the walls of the case laterally, also pushes back with the force of fifty thousand pounds to the square inch on the head of the cartridge, and the whole cartridge being made of elastic brass stretches to the rear and , in effect, give the breech block a sharp blow with starts it backward. The front end of the cartridge being tightly held by the friction against the walls of the chamber, and the rear end being free to move back in this manner under the internal pressure, either one of two things will happen. In the first case, the breech block and the head of the cartridge may continue to move back, tearing the cartridge in two and leaving the front end tightly stuck in the chamber; or, if the breech block is sufficiently retarded so that it does not allow a very violent backward motion, the result may simply be that the breech block moves back a short distance and the jerk of the extractor on the cartridge case stops it, and the gun will not operate.
However this difficultly can be overcome entirely by lubricating the cartridges in some way. In the Schwarzlose machine gun there is a little pump installed in the mechanism which squirts a single drop of oil into the chamber each time the breech block goes back. In the Thompson Auto-rifle there are oil-soaked pads in the magazine which contains the cartridges. In the Pedersen semiautomatic rifle the lubrication is taken care of by coating the cartridges with a light film of wax.
Blish Principle….There is no doubt that this mechanism can be made to operate as described, provided the cartridge are lubricated, …. That this type of mechanism actually opens while there is still considerable pressure in the cartridge case is evident from the fact that the gun does not operate satisfactorily unless the cartridges are lubricated.
While neither the Garand or M1a are retarded blowback actions, cases are still stretched by the residual blow back effect engineered in these mechanisms. This pressure curve is of the Garand gas system. Do notice that unlock is complete when pressures are 600 psia. The case is being extracted for a distance of half inches before pressure is zero.
These cases were fired lubricated with Johnson Paste wax, as can be seen with the case gage, the shoulders have moved, as the case moved, during extraction. These cases were sized between the Go and No Go of this gage, and yet, because they were pulled out of the chamber during the residual blow back period, the case shoulders moved forward to fill the void. If these cases had not been lubricated, instead of the shoulder folding out to the contours of the chamber, the case sidewalls would have been stretched, damaging the case and leading to case head separations.
Case life is not a concern of the military, they don’t expect Soldiers to reload their ammunition, but for civilian shooters desiring to maximum the case life of a round fired in a gas gun, case life can be greatly extended by the practice of cartridge lubrication. Case lubrication will prevent the case neck and shoulders from adhering to the chamber, so that when the case is extracted under pressure, case sidewalls are not stretched. I am of the opinion that lubricated cases will improve extraction reliability because pressure is not zero, some part of the case is being dragged against the chamber. This is the primary reason M16’s have “extractor lift”. The case drags in the chamber and follows off the bolt face. Increasing case to chamber friction always reduces extraction reliability. Lessening case to chamber friction always improves extraction reliability.
The picture below showing case head stretch are typical of dry cases fired in a M1a or a Garand. Those were from a shooting bud and they were five times fired. Scratches are from a bent paperclip inserted in the case mouth, I was trying to find the side with the deepest stretch ring.
When I resized my cases, I sized the cases to gage minimum or if the brass is to be fired in only one M1a, I sometimes push the shoulder back 0.003” from the chamber headspace. It turns out, it is easier just to size to gage minimum. Primarily I use RCBS water soluble case lube, because the stuff sizes well and is easy to wash off in soap and water. I size my gas gun cases in small base dies. I set up the dies with cartridge headspace gages.
Most of rounds I fired I coated with Johnson Paste wax. I believe the hard, durable wax in Johnson Paste wax is ceresin wax, the same wax that John Pedersen used in his wax coating of the 276 Pedersen rifle:
Patented Nov. 4, 1930
PATENT OFFICE JOHN DOUGLAS PEDERSEN, OF SPRINGFIELD, MASSACHUSETTS
http://www.google.com/patents/US1780566
In the preparation of cartridges having metal cases for storage and for use, it has been found desirable to apply to said metal case a relatively thin coating of some protective substance which will preserve said metal case for comparatively long periods of time against-deterioration, such as season cracking. In the present invention, the material for said coating has been so chosen as to perform the additional function of acting as a lubricant for the case of the cartridge, both for facilitating introduction into the chamber of the gun and the extraction thereof after firing. The most suitable wax which I have found for this purpose and which I at present prefer is ceresin, a refined product of ozokerite; but I wish it to be understood that other waxes having similar qualities may exist which might serve equally well. Some of the desirable features of ceresin are that it is hard and non-tacky at ordinary temperatures having a melting point somewhere between 140 and 176 Fahrenheit. It is smooth and glassy when hard and does not gather dirt or dust. However, when the ceresin on the cartridges is melted in the chamber of a gun, it becomes a lubricant.
Other lubricating waxes have been employed for coating cartridges, and the method most generally pursued for applying said coating to the cartridge case has been to prepare a heated bath of a solution of the wax in a suitable solvent, dip the cartridges therein so that a film of the solution will adhere thereto, and finally withdraw the cartridges to permit the solvent to evaporate from the coating film. This former process is comparatively slow and has been found lacking in several important respects.
Even though it was a time consuming process, for match ammunition, I preferred coating my match cartridges with Johnson paste wax. And it was for precisely the same reasons as John Pedersen gave:
It is smooth and glassy when hard and does not gather dirt or dust If you have ever shot in an XTC rifle match, you are on the field all day. None of the ranges I shot had running water, for bathrooms: you went around the berm. Because I could not wash, I preferred to not have industrial or automotive greases all over my hands. Another thing in XTC matches, you don’t get a lunch break. You munch on whatever you brought in the few minutes of between relays and preparation periods. I did not want to be eating axle grease with my sandwich. So, for match ammunition, I preferred Johnson paste wax.
At Camp Perry in cold weather I had bolt over rides with some of my Johnson paste waxed rounds during a rapid fire stage. This stopped when I polished the rounds with a rag. Previous to that I shot the rounds with swirls and gobs of paste wax but evidentially that caused sluggish round rise in the magazine in cold weather. From then on I polished my rapid fire rounds and have never had a bolt close on an empty chamber even in rapid fires sequences in snow. For slow fire rounds, I left the gobs of wax alone.
With a 168 SMK/Hornady/Speer/Nosler match I used 41.5 grains IMR 4895 or AA2495 whatever was cheaper. I shot estate sale IMR 4895, I shot 32 pounds of AA2495 through my M1a. AA2495 is a copy of IMR 4895 and the Chinese made version I bought shot exceptionally well. I cut loads, sometimes by half a grain in 90 + weather, but of the brass sectioned below, most of the time I shot a 168 Match with 41.5 grains AA2495/IMR 4895. I also shot 175 SMK’s with 41.0 to 41.5 grains IMR 4895/AA2495. These are hot loads, especially 41.5 grs IMR 4895 and I used them at 600/1000 yards.
Since earning my Distinguished Rifleman Badge I have been loading lighter loads out to 300 yards. I will push a 168 Match to just 2550 fps, such as the chronographed surplus powder load I developed. At 600 yards I still bump up loads to 41.5 grains IMR 4895. Velocities of my loads are as below. These velocities were all measured in a Douglas barreled M1a with lubricated cases. While velocity is not a direct measure of pressure, if pressures were high, and dangerous, as claimed by Hatcherites, then I ought to see abnormal velocities with lubricated cases.
Code:
168 Nosler 41.0 Military Surplus MSG 4895 IMI Match CCI 200 OAL 2.750"
21 June 2008 T = 85 °F
Ave Vel = 2552
Std Dev = 11
ES = 27
High = 2565
Low = 2538
N = 5
168 Nosler Match 41.0 AA2495 LC72 WLR OAL 2.8
29-Apr-04 T= 78 ° F
Ave Vel = 2517
Std Dev = 21
ES = 68
Low = 2486
High = 2554
N = 17
168 gr Sierra Match 41.5 gr AA2520 LC Mixed WLR OAL 2.800
22-Apr-99 T = 75- 80°F
Ave Vel = 2601
Std Dev = 14
ES = 38
Low = 2584
High = 2622
N = 10
175 gr Sierra Match 41.5 gr AA2495 LC87 W/W OAL 2.800
29-Jun-96
Ave Vel = 2579
Std Dev = 13
ES = 40
Low = 2564
High = 2604
N = 10
174 FMJBT 40.5 grs H4895 wtd, lot 4501 LC mixed WLR OAL 2.800"
18 May 2008 T = 71 °F
Ave Vel = 2524
Std Dev = 36
ES = 90
High = 2587
Low = 2497
N = 5
174 FMJBT 41.0 grs H4895 wtd, lot 4501 LC mixed WLR OAL 2.800"
18 May 2008 T = 71 °F
Ave Vel = 2594
Std Dev = 14
ES = 30
High = 2609
Low = 2579
N = 5
174 FMJBT 41.5 grs H4895 wtd, lot 4501 LC mixed WLR OAL 2.800"
18 May 2008 T = 71 °F
Ave Vel = 2593
Std Dev = 15
ES = 42
High = 2613
Low = 2571
N = 5
I don’t like the feel of greasy cases and if I had time between matches I washed the cases to remove the RCBS lube, primed them clean, loaded them with powder and bullet, and after that, applied paste wax. If I did not have time I fired the cases just as they came out of the die, minus whatever RCBS lube which was lost in handling. I never had a primer dud, even though I primed hundreds of cases that had a RCBS lube coating. I ran a number of experiments with various lubes. Leaving thick coatings of heavy greases is objectionable as grease particles are blown into the air, some out of the action, some out of the barrel. I had 1000 rounds of 7.62 CAVIM and I fired most of them in a FAL. FAL’s are very hard on brass and I had this stick wax, so I experimented with the stick wax. Stick wax is tenuous grease used to lubricate saw teeth. It really sticks to stuff. I dropped lumps of stick wax in a plastic bag with handfuls of CAVIM and shook vigorously. Both case and bullets were unevenly coated with globs of stick wax. When I fired this stuff it was as if a grease bomb went off. The mechanism became coated in stick wax, and I was coated in stick wax. My shooting glasses had to be frequently cleaned, my hands were greasy, my clothes were greasy, overall, it was messy. Because it was so messy, I later spent hours wiping the cases to reduce the amount of stick wax covering the cases. This was better, but I still had stick wax over my hands, clothes, and the stuff does not wash off easily. Stick wax does exactly what it is supposed to do: stick to the surface.
Some of the lubes I tried include Imperial sizing wax, Mink Oil shoe polish, Hornady Unique case lube, Lee lube, wire pulling wax, lubriplate greases and many combinations of axle grease and wheel bearing greases. I oiled cases with automotive oil. I will never again use stick wax. I never ever had issues with case damage or unusual case damage such as “serrations” as one Hatcherite claimed would happen with Imperial sizing wax. Any one claiming such nonsense has to be confabulating experiences from their own fantasy land of physics.
After much testing , I came to the decision that I preferred dry coatings. Even so, with RCBS water soluble, after all the handling that occurs with trimming, priming, dumping the powder , seating the bullet, the amount of RCBS case lube left on the case does not leave objectionable residue in the mechanism or eyeglasses.
The picture below are of sectioned cases, R stands for reloaded, R5 five times reloaded, etc, all of these cases the shoulder was set back about 0.003” and the cases fired in my M1a. I do not visually see any evidence of case wall thinning from those cases reloaded 5 times (6 times fired) , R18, or R22. As long as the case is not excessively stretched during firing or extraction, there is no reason for the sidewalls to thin.
My basic conclusion is that if cartridge brass does not failure through case neck cracks, body splits, and you have not stretched them so they develop case head separations, you can load them until the primer pockets get too large. I quit shooting these cases because it became easy to insert the primers in the pocket. Loose primer pockets will release primers when the round is fed into the chamber. I have had jams due to loose primers in a number of semi automatic mechanisms. I had lots of jams in my 45 ACP M1911’s due to range pickup AMERC brass. AMERC brass was some of the worst I ever used, oversized primer pockets were just one issue, and I had primers come out of primed AMERC cases as they were fed into the chamber.
I found that I needed to periodically ream the primer pockets: the pockets became shallow. Don’t know why unless the primer pocket collapses over time. As incidental contact with the primer can cause a slamfire or an out of battery slamfire, keeping the primer below the case head is a safety critical issue.
I believe that lubricated cases will produce more consistent accuracy than dry cases. Chambers foul and they foul unevenly. I am of the opinion that irregular binding occurs when cases adhere to the chamber. Lubricated cases evenly transfer the thrust to the locking mechanism. For their roller bolt rifles, which use gas lubrication to break case friction, HK used to make a statement to that effect on their web page.
I don’t think it is any coincidence that all match 22lr ammunition is liberally greased from rim to bullet tip. I am also of the opinion that all semi automatic mechanisms eject more reliably if the case to chamber friction is reduced. While the M1a has been developed to an accurate service rifle, I believe any inaccuracy due to case friction is in the noise level for this mechanism.
I can say I earned my Distinguished Rifleman’s Badge and won a Regional Gold with lubricated cases in the M1A. My accuracy and function with lubricated cases was more than acceptable. My case life was orders of magnitude greater than those who fired dry cases, so I saved money. That has to mean something. I shot two barrels out on one M1a, all with lubricated cases. I did not notice any unusual wear patterns on the bolt, operating rod, receiver.
As long as the cases go bang in your rifle, and that you only fire loads that are within book value, with powders appropriate to a gas gun, I am going to recommend that you lubricate your cases to extend your case life and that you go to a faster rifle powder.
