I have used a two part epoxy putty, its petroleum resistant. It comes in a stick at the auto parts store. The stuff I bought was call fast weld. The outside of the stick is a light grey and the inside is a dark grey. You break you off a piece and knead it till its all one color. Then make it into a roll a little bigger than a casing and shove it into the chamber. This stuff cures in like 20 minutes. It gets warm when you are mixing it. Don't dilly dally with it. When it sets up its like a rock. It doesn't swell so don't worry about that. but clean the chamber area with alcohol really good to make sure there is no oily residue there to help the putty cure. Then I used a gel type bore scrubber. I filled the barrel up with the gel bore scrubber then I left it standing of course and covered the muzzle end with a tube type balloon. When you scrub it use a BRASS ROD and a Bronze brush, don't use a steel bristled brush. When I was done I knocked the putty out with the cleaning rod that comes on the Mosin tap it gently and it will come out in one piece, I then ran a 20 gauge shotgun bush on a section of cleaning rod in my drill to clean up the chamber in case there was any left over putty in there. Hope this helps
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