We had 40mm HEDP(high-explosive-duel-purpode) rounds for the M203 and the belt-fed version(fed from a large ammo can)for our MK-19s. Those are actual weapons of war that we used to kill more Hajis than with those pissy little 5.56 rifles.
I am not familiar with 44mm.
44mm are just like the 40mm but 4mm more powerful.
They took away our MK-19's before we got in country. Something about potential for civilian casualties blah blah blah.