Savage 64 semi-auto with 21" bbl that just begged to be close-encounters shortened. Hacked off 4-1/2", filed the muzzle square, smoothed it out with a run of 3M grits, lightly chamfered the muzzle rim, polished with fine steel wool. Used a brass 3/8" round head slot screw in a hand drill along with valve grinding compound for the crowning. At 12 yards with an "assisted" offhand stance it's not a bad plinker.
before ...
https://i.imgur.com/D5B2RTR.jpg
after the gelding ...
https://i.imgur.com/H0vHpNX.jpg