01-07-2020, 01:59 PM
LRRPF52 Wrote:If you use a piston system, the gas block really needs to be securely mounted to the journal, as in pinned with no gas leakage around the seal of the ID of the block and the OD of the barrel.
The barrel needs to be bedded into the upper, either using thermo-fit, compound, or shim stock with compound.
The upper receiver face needs to be square, which is often out of square after anodizing inconsistencies in surface thickness.
With the combined effects of a larger projectile and the asymmetric forces imparted on the rifle from the external piston operation, we normally see measurable and predictable accuracy loss on piston guns.
Some of the more dedicated companies who invested a lot into making their piston guns as accurate as possible had to do a lot of tweaks across the rifle to get them reasonably accurate, the main 2 off the tip of my head being Hk and PWS.
DNS has had good accuracy reports from his piston set-up, not sure what he's using exactly, but he's also shooting suppressed.
I always use the Stoner Internal Expansion gas system, as it is inherently more accurate with minimal asymmetric forces exerted on the barrel.
I check/square my uppers and bed my barrels, bed the gas blocks, balance the torque on the muzzle device, balance the torque on the barrel nut, use equal torque on all my rings, correct torque on the scope base fasteners, I like tight-fitting receivers personally, a great trigger, a bunch of little tweaks with the bolt, ejector, extractor, barrel extension, and certain shooting techniques that I don't need to do with the .223 AR.
@LRRPF52,
Thanks. I did a LOT of that. I'll make a new build thread, with pix, when I get a barrel back from Alexander Arms.
Ken