In D1, especially as a low level player Id run out of ammo constantly. In D2 I only was in danger of completely running out of ammo like once ever? In D2 I really only run out of ammo for my heavy weapon and even then it depends on what Im using. Also there's really no need to even use power weapons on bosses when you have a Coldheart. That thing melts and you get tons of ammo for it.