Reloading the AR10's
- Thread starter rborensr
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Yes, if you want reliable feed and extraction. You should small base size all cases to ensure clearance between chamber and round. You should use cartridge case headspace gages to set up your sizing dies, and have that gage on the counter when sizing cases, to check that the different characteristics of brass, between manufacturers and times fired, has not changed the cartridge case headspace. Shoot enough brass and you will find that some brass, the shoulder sets back correctly for the same die setting, others, the die has to be adjusted. I recommend sizing brass less than 0.003" from chamber headspace, or if you really don't know the chamber headspace, size to gage minimum.
You should use the least sensitive primers in these mechanisms, though AR10's and AR15's have few out of battery reports, they have plenty of in battery slamfire reports. The primary cause of slamfires is sensitive primers. I recommend CCI #34 primers or Tula mil spec as these are the appropriate primers for this mechanism. I do not recommend the most sensitive primers, stay away from Federal. I do not recommend benchrest primers as the manufacturer has stated that these are not appropriate as the cups are thinner. You should ream primer pockets to depth to ensure that there are no high primers either! A firmly seated primer in a shallow pocket is ready to ignite, if hit hard enough.
For 308 cartridges you should use powders that go, from the fastest, IMR 3031, to the slowest IMR 4064. The "standard" for the 308 is the 4895 series, that is IMR 4895, H4895, AA2495. The 308 cartridge was developed in WW2 with IMR 4895, this is the first powder that should be tried. As a rule, faster is better in a gas gun, I shot several cans of IMR 3031 in my M1a and it worked perfectly. Slower is not better. Slower means ripped case heads, sticking cases. It all has to do with the timing designed into gas guns.
This 7.62 pressure curve, that little insert is incredibly important. That is the pressure drop of the cartridge after the bullet leaves the barrels
In this figure, you see that unlock occurs while there still is pressure in the barrel. This is the "residual blow back effect". This is deliberate, it increases the amount of time energy is available to push the mechanism, it is lower than the rupture strength of the case, and it helps "pop" the case out. This is why gas guns are not flexible in their choices of powders, the pressure curve and timing have to correctly matched.
Seat bullets to magazine depth or a little less. You do not want a bullet jammed into the throat. The gun will shoot better than you if you use jump insensitive bullets. For a match bullet, it is hard to beat the 168 match types, very accurate, very jump insensitive. Keep pressures mid range. About 2550 fps with a 168 in a 22" barrel, about 2650 fps with a 150 in a 22" barrel. Attempting to push a bullet faster than the timing allows will only result in jams and ripped case rims. Assuming your extractor does not fall out!
So, the basics, full length size all cases, preferably with a small base die. Set dies up with a cartridge headspace gage. Trim cases. Ream the primer to depth on new cases, prime with the least sensitive primers you can find (CCI #34, Tula mil spec), and use powders in the 4895 range with the 308 Win. Keep your loads mid range, don't try maximum loads in gas guns.
Blue68f100
Member
If you all ready have the std dies for all means use them. I have not needed any SB dies is any of my simi-autos. All of my AR-s have min spec match chambers and I don't need them. As long as you can get the shoulders back to spec you should not have any problem. Like previously mentioned 0.003" is a good target. Case gauges makes it easier to setup up your dies. Now if your over gassed it can cause timing problems. I run adj gas blocks on all my AR's. Now I anneal every cycle keeping the necks soft so I do not have to adj my dies has the brass work hardens.
I have the sizing issues under control. It's just that in the books, they list the service rifle as the M1A, and they have different issues that the AR's do. I heard that you can use the regular bolt action loads on the AR's because their gas systems aren't as sensitive to the burn rates.
There is one absolutely definitive way to find out if the advice you heard is good. Go out and load "regular bolt action loads" and tell us how things turned out.
RainDodger
Member
Mid-power standard .308 loads work great in my AR-10. Never a problem. I do anneal every time and my dies happen to be small base only because that’s what I had on hand when I acquired the rifle.
Blue68f100
Member
You should not have any of the problems that the M1A does due to design of the AR's gas system. Just watch to see which way and how far the brass is ejecting. This will help you determine if your running too much pressure. Need to compare this to factory ammo though to know if its normal for your gun. Some guns are over gassed and other are minimal. I like tuning the gas system so my brass is not dented or being overly stretched during extraction. I have some 223 brass that has over 10 reloads and still going strong.
Thanks, this is what I was looking for.
redbullitt
Member
MY ar10 always did best with loads a little reduced from what my bolt guns like, and it seemed to show pressure signs a little earlier. I think you will find it less finicky than the M1A.
Not super specific, but hopefully helpful!
Not super specific, but hopefully helpful!
CLP
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I reload according to this article by Glen Zediker.
Very helpful re: use of SB dies, brass choice, etc- even though it's written for M14/M1A reloading much of it applies directly to AR10s as well.
It's not like either of these rifle systems is gentle on brass. Good reading though- seriously- give it a perusal.
Very helpful re: use of SB dies, brass choice, etc- even though it's written for M14/M1A reloading much of it applies directly to AR10s as well.
It's not like either of these rifle systems is gentle on brass. Good reading though- seriously- give it a perusal.
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