Algodoo

Up/down to aim, press f to fire.

Tank-calibre cannon with autoloader, typical for small naval vessels.

Features:
-pretty realistic sliding block breech, that allows very powerfull cartridge. Gun recoil automatically opens it, and inserting new round automatically closes it, so the upper part is fine semi-automatic gun on it's own.

-The gun can elevate within 70 degrees, while ammo storage is stationary