Help my Grendel pistol isn’t accurate

[LRRPF52]

Next I will ask what the assembly process was for installing the barrel, and was your upper receiver face square?

I true or check that all my receiver faces are square, then find the best barrel extension-to-upper fit among a handful of uppers I have at-hand.

I do not buy uppers anymore and just hope that they fit ok, but mate up the barrel in question with that upper to reduce and eliminate slop.

I also don’t let the barrel near the upper until it passes a series of dummy cartridge checks I have to see where chambers are at in terms of distance to the lands.

I also record what the gas port diameter is, and measure the diameter of the gas block journal so I can mate the gas block tightly (slop is the enemy for reliability, but friend of ease of installation for DIY builders, not a good combo).

All 3 of the Grendels listed above have bedded or thermo-fit barrels, where the barrel is mated to the upper tightly. One of the 12” barrels took me at least 45 minutes to pound into the upper with the tightest interference fit I’ve ever experienced with an AR-15. The others are bedded with Blue Loc-tite.

For optics mounting, I use a torque wrench to ensure all fasteners are consistent to the recommended specs from the mount and ring manufacturer.

Rings get Blue Loc tite on fasteners.

I think applying gas gun fundamentals will tighten your groups though.

I noticed what Klem was talking about first thing as well, with the backwards Warne mount.

If you set the optic up for ideal eye relief, it will be easier to shoot. The Warne mount (and any cantilever mounts) are designed to locate the optic for optimum eye relief on AR-15s.