20 years ago we were stabilizing Rifles and MG from choppers, boats and ground transport. Never caught on for small arms.No one could sell the Military on it. Now tanks, thats another story.
Look through the early history of the semi-auto pistol you will find recoil springs over barrels, around barrels, connected to rods attached to barrels, behind the bolt, under the bolt and in the grip. Half slides,full slides, inturnal bolts, drop block, toggle lock, turn lock, cam lock. The ammo reload systems have been single shells into an interal mag,exturnal stripperclip loaded, internal stripperclip ejected when empty, bottom and top ejecting magazine,side loaded through a gate or apature, and last but not least semi-auto revolvers. The end of the 1800s and beginning of the 1900s was rife with the most variety of semi auto pistol variations. I've been forunate or cursed with the disasembly of quite a few of these in the process of cleaning and getting them ready to liquidate for my father.
I know I have probably forgotten something.
As to the future I think all of the classic autos and revolvers will be manufactured is one form or another. The way they are made might be radically different (3D copy macine). All projectiles will be lead free with polymer cases,caseless, and a few traditional. Propelents will include more efficient powder, gas,liquid and magnetic induction. We might have a smart bullit. OOPS, we already have most of these things now.
Never give guy too much coffee, Cheers, ts