####, it's really the M14. Lemme 'splain...
The closest to an ex-military rifle that we can actually own AND shoot. 7.62 NATO caliber. 20rnd box mag. Uses a piston/tappet to operate the action via gas. Equipped with a flash hider (I remember these termed 'flash eliminators', anyone else?).
Some obvious objections; different locking system, pistol grip, rear sights, cocking handle, other things I'm sure....
The G3's also similar, but the radically different operating system (plus the grip) places it in second, regards the question. Also prohib, FFS, dammit