Algodoo

a grenade launcher that automatically opens the breech for you
(id make it have a ejector but idk how)
just pull the trigger, the breech should open, take out the casing
and load another round in, close the part the grenade sits in, (maybe push the green lever forward
if it doesnt lock all the way) and repeat! green lever opens the breech prematurely.
not to scale, as i suck at that, but i hope you liike it!
credits to johnfromthewest for the grenade round.
update: added an extractor