Don't worry about the fast twist with light bullets. My Pac-Nor 1:8.5" twist barrel shoots the
Barnes 26 Grain Varmint Grenade into the .2's, at 4,110 fps in a bolt action (using RL-10x). In my Colt M-4 with a 24" Hart 1:9" barrel the
24 grain Hornady NTX shoots reliably below .5" in initial load testing with ACC LT-32 powder. In the photo below the limiting factor is my trigger goofs and the Wolf 223 Small Rifle Primer. The Winchester Small Rifle Primer or Remington's 7-1/2BR should shrink groups over the Wolf which is a magnum primer. However, keep in mind this rifle is not semiautomatic, it has no gas port in the barrel so it operates as a straight pull bolt action. This is to circumvent California's confusing assault weapons law so it can be used to hunt varmints on public lands without drama. Next step is to work up loads with RL-10x which should increase velocities without pressure problems.
Colt M-4 ten shot groups @ 100 yards, red diamonds .5" square.
Your initial groups with factory ammo is very encouraging, outstanding really! I recommend that you consider using one of these in place of the rear pin:
http://www.sinclairintl.com/gun-parts-t ... d7591.aspx I also tightened the front pin lateral slop with custom honed shims (revolver cylinder end shake bushings honed between two Carborundum stones to 1/2 the clearance of .009"). The less the upper flexes on the lower, the better. However, your accuracy is already so good the varmints will probably never know the difference. Building these things is fun!
