Shilen barrel chambered in 204 Ruger...barrel nut indexing shims

[tobnpr]

Upon re-reading I'm not clear which surface was being referred to in #17, but I'm referring to the nut- not the barrel extension.
Removing material from the nut to get it to clock correctly impacts no other components.

 

[dfrosch]

I'm talking about the face of the upper receiver, in front of the threads. This is the surface that the flange on the barrel extension butts up to.

And generally speaking, you don't need to clean this face up completely. I usually lap, clean inspect and repeat until the face is 80 to 90% cleaned up. This would get the OP closer to timing the barrel nut correctly. The rest should probably be made up with torque, up to 80 ft/lbs.

 

[RPR 6.5 slave]

Gentleman, Thank you for the input. No I am not a machinist. I have been in contact with Shilen and the maker of the hand-guard. The hand-guard came with (3) .003 shims. The problem started when I realized that the shims supplied were too small inside diameter. The barrel measures .936 at the gas block step. then it has another step up that is tapered up to the barrel flange, where the nut tightens to apply pressure to torque. This diameter is 1.005. The whole issue is because I needed a hand-guard with an inside diameter of 1.400 or larger to accommodate enough clearance for an adjustable gas block (Superlative Arms) SABO-DI-936cs. This is the block I chose because of the limited suppliers making heavy target barrel adjustable blocks. I have built many ar15 rifles in the past but I have never built one with a (heavy target/ Varmint) barrel. I never saw this dilemma coming. But now that I am into it this far, I want it done right.

 

[dfrosch]

Think you'll like the gas block. Probably won't need to use the bleed off for a 204 Ruger. Just set it 2-1/4 turns from closed and adjust 'til the mag holds the bolt open.

 

[RPR 6.5 slave]

Think you'll like the gas block. Probably won't need to use the bleed off for a 204 Ruger. Just set it 2-1/4 turns from closed and adjust 'til the mag holds the bolt open.

Thanks, I think I will like it too. Once I get this barrel nut issue resolved. If I didn't want to run adjustable block I would have this thing up and runnin. sigh....!

 

[RPR 6.5 slave]

Question from an admitted AR ignorant guy. How much interference is there at the gas block? Doing a quick search I found shims that have an ID of 1", which would make me think seriously of taking a file to the block, if they could be used.
https://www.wingtactical.com/firear...ries/aero-precision-ar15-barrel-nut-shim-kit/

BoydAllen, Thanks for the heads up on the link for shims. I got hold of aero precision and they hooked me up with a shim pack of .001 shims and I now have the upper assembled. The part # APRH100267c, AR15 BAR shim pack, may be of help to someone else later down the road. I really appreciate the tip.