In handuns I would use a 9mm and, in semiauto guns I would use a semi auto Ak-47
Find the high ground and quietly make head shots from a safe distance...
50 rounds of .308 on tap is a big plus.
Yep, silencers/noise suppressors are the ticket. 308 rocks, especially at distances over 300+ yards. The 223/5.56x45mm is a good round out of many rifles out to 600+ yard. Of course both rounds are excellent up front. The 308 will be a bit louder up close even with te suppressor but still a good weapon. .223/5.56 suppressed in link.
Another 308 longer video
308 rifles are a bit heavier and the capacity isn't as high. It is a very good round for sniping. I'd have no issue using one in a fixed location where I ddint' have to carry all of my ammo with me. It will reach out further then .223/5.56. It get things done for sure.
Of course a .22lr will have no noise if suppressed, but it won't reach out near as far as the .223/5.56 and no where near as far as the .308 Win./7.62 NATO (7.62x51). The .22lr's effective range is really no where in the running. Maybe a .22 Magnum can reach out a bit more then the .22lr but will still fall short of the .223 and especially the .308. I can't see carrying thousands of rounds of .22lr even for confined locations when .223 gets it done better.
Another 308 and it can be movie quiet
Yeah, the sub-sonic makes a difference but when you're all of a sudden up to your elbows in skinnies you don't really want to have to cycle each round by hand. Same with the .223. Quieter then a church mouse but hand cycling sucks.