Mass Effect 1/2

[Belle Hibiki]

Ammo is stupid. Especially after they went to ridiculous lengths in the first game to explain away the reason for guns not having ammo in the first place.

Yeah, because we're known to revert to older technology in the face of some kind of difficulty with the new stuff. *Scoff*

I prefer to imagine the guns as being exactly the same, but that new guns put out so much heat that they require these clips to be able to fire without going into overheat after one or two shots. (I assume this is the canon reason, as well.)

Explained possibly by defense tech all over the place getting better and better, what with armor and biotic barrier and all. The ammo-less weapons likely still exist, but their damage output would be utterly ineffectual against the new tech.