They should've made Black Hammer an Exotic. So people can't use the Black Hammer and Gjallarhorn at the same time. Anyway. They did it because it was a pretty OP perk, and instead of nerfing the dmg of the Black Hammer, they just decided to take away some reserve ammo, and have it so the ammo doesn't come out of the ether. So it's probably still effective, but they just did a little tinkering to take it from Exotic tier to Legendary tier. Or people where 2 busy destroying Atheon, Crota or the bosses in PoE ᕦ( ͡°╭͜ʖ╮͡° )ᕤ