oops. Man am I embarrassed ! ... brought a design hat to a brainstorm ... sorry about that, chief !
here’s my weirdest idea so you guys can laugh ...
sabot encased projectiles are scooped up and aligned with the barrel by a cam (no cartridge). The firing chamber behind the cam has electronically controlled injectors to meter a liquid solution of hydrazine and other, more nasty stuff. Firing is by a high voltage spark. This was from musings in 1980 or so. . . for a deck mounted machine gun.