Idea for bedding barrel extensions

[grampajack]

Not with any bolt which wasn't already on the edge of acceptance - which I would have pitched on initial test fit before I ever got to the lapping stage. You're not the bolt moving much - I've not measured the lug thicknesses before and after, but it's not removing bulk material like what turning the bolt to true the lugs might.

What epoxy do you use? The one I tried I wasn't real happy with the temperature rating. Supposedly it was 600, but I heated it up to around maybe 350 to see and it just peeled right off. I was thinking maybe try some JB Weld extreme temperature next.

 

[Varminterror]

I use Devcon steel. Putty if not using a shim, liquid if using steel shims.

 

[grampajack]

I use Devcon steel. Putty if not using a shim, liquid if using steel shims.

Any idea what the safe operating temp for that is?

 

[MachIVshooter]

I wouldn't trust a "paint" to be uniform enough, nor durable enough to serve as a shim. Cerakote goes on incredibly thin, wanna say 1-2thou each coat, so you'd need a lot of coats, which then could get you into the same uniformity issues as any paint.

I personally use stainless steel shim stock around the barrel extension if I ever end up with something undersized. If I can't get a 1 thou steel shim around the extension, it doesn't need shimmed.

When I really want them to be solid, I bed and fix the extension to the upper. It doesn't matter much when you're talking about $50 forged uppers tied to $300-500 barrels.

Personally, I wouldn't waste my time thinking about a coating or paint to "shim" by extensions. I think that would be a bandaid on an axe wound at best - your mind might feel better about it (mine would not), but I'd be willing to bet it doesn't actually improve long term fit.

This. If it's loose enough to be problematic, you'll be able to get steel shim stock in there, which is a far superior solution to any built-up enamel. Shim stock is inexpensive, and under .010", it's easy to cut very precisely with regular scissors. Getting the really thin stuff to go in right without crumpling or tearing can be a challenge, but the sheets will give you more than one try.