Don't ever use any fast setting epoxy for anything !!! They are not very strong ,have poor shelf life, and deteriorate over time !!
A filler should be used to minimize shrinkage. Brownell's Acra-glas is still about the best .The rifles I used it on 40 years ago are still tight [no shrinkage] and hard !! Make sure you remember to wax all metal parts and to fill up things like screw holes with clay.
And Watson , bring your revolver !