I’m not sure how the drop rate for the heavy ammo works, however, I do see some weirdness at witch the drop chance occurs. For example: When I have a heavy exotic weapon and some armor pieces that should increase the drop rate of heavy, the purple bricks seem extremely rare. (I’ve gone through whole strikes where only about three bricks of ammo have dropped, or not at all) However, when I have a legendary heavy weapon with the same armor that should give me more heavy ammo, the purple bricks seem to drop like candy. Just seems weird to me.