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Gas port pressures

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Gas port pressures was created by Hank in Arkansas

I recently bought an Armalite AR10B, and haven't reloaded for it yet. After I do, I'll share my results here. Meanwhile, I've got a question for any experienced handloaders of the AR10, or anyone who's studied the AR10 gas system. It's generally accepted that the M14/M1A platform is fairly adaptable to variances in gas port pressure. In other words, lots of powder burn rate curves are within tolerance limits. On the other hand, the AR15/M16 platform has a reputation for problems if gas port pressures aren't fairly close to the design specs. Of course, there are lots of acceptable powders that work well, shown in all the loading manuals.

Does anyone know how the AR10 platform stacks up? Virtually all the autoloading rifle load data I see for 7.62mm is based on the M14/M1A family, and none even mentions the AR10. Are the "best" AR15 powders the best for the AR10, or is it more flexible like the M14/M1A is? My M1A loads are based on WW748 and AA2520. I have several other possibley suitable powders on hand, including AA2230, IMR4064 Benchmark, WW760, and VitN160.
15 years 5 months ago #547

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Replied by weshowe on topic Re:Gas port pressures

Hank,

Can't vouch for gas ports on the AR-10. Most of my experience with gas guns was with a Garand and the 3 M1A'a I've had. With these powders in the medium burn range are best (IMR-4895, IMR-4064, Varget, Accurate 2520, or Winch 748).
A call to Armalite may answer your question.
IMHO you can't go wrong sticking with any of the above powders. In fact I'm putting some Accurate 2520 and Sierra 155 gr. Match Kings through mine on Thursday. I'll report back to you folks.

Wes
15 years 5 months ago #551

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Replied by crux on topic Re:Gas port pressures

I'll have to second wes, you'll probably have to talk to Armalite. I won't be surprised if they repeat the mantra "only quality factory amunition". Their tech notes have numerous complaints about hand loading. But you might be able to get the spec range it's desinged to tollerate.
15 years 5 months ago #556

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Replied by Hank in Arkansas on topic Re:Gas port pressures

I did send an email to Armalite on the gas port question. They haven't replied so far. Possibly they won't reply, in keeping with the admonition to never handload. Anyway, I'm proceeding on my own with loads, using commonly recommended service rifle powders that are often used in the M14 family. I've already discovered that some previously loaded .308, that functions just great in my M1A, won't chamber smoothly in the AR10B. That particular ammo was loaded with a standard RCBS X-die. So I made up some dummies with an RCBS small base die, and they function fine. I've loaded some ammo, but haven't been back to the range yet. I'm also trying to be very careful to stay close to factory overall length. I've noticed that bullets get scratched a bit as they transition from the magazine into the chamber. I think they're dragging over the bottom two recesses where the bottom two bolt lugs mate up as the rifle goes into battery. No biggy, though. Anyone else out there finding it necessary to use small base dies in the AR10? I suspect they have minimum SAAMI chambers.
15 years 5 months ago #633

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Replied by bigwheel on topic Re:Gas port pressures

Been at it for 11 years with a 10t and never had any problems. Only thing I do out of the ordinary is
use a lee factory crimp die. Plenty of nato loads that can be approximated so I never have tried to
veer off the beaten path. 150 to 170 grain pills.
15 years 5 months ago #640

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