.30 carbine subsonic rifle
I came accross a random post the other day discussing purpose built subsonic rounds/rifles. BRG3 mentioned that .30 carbine was probably a good choice, being straight walled and packing enough punch to send a heavy .308 diameter round downrange, but not so powerful as to go supersonic. It got me thinking... I tried loading some .30 carbine rounds in an AK74 magazine and they seemed to fit pretty well. its long enough that if you loaded 174 grain bullets in the .30 carbine case they would (look rediculous &) just fit in the 74 mag. About 33 of them fit in there, and seemed to leave the magazine fine, if not a bit low. you would need to add just bit more thickness to the follower to hold the last round in place- otherwise is slips out. There isn't an ak bolt with a small enough bolt face pocket to take the tiny .30 carbine, but maybe TIGing in a bushing to reduce the diameter might work... like the 2xtm . I noticed Northridge has demilled .30 carbine barrels....