Shape changing

[MrJupiter]

...As for the "Ammo", if it is a robot we're talking about, that makes sense. The ammo is stored inside the robotic body and part of the transformation process makes it usable.

But for a living person to suddenly turn their arms into guns that fire bullets does seem silly. Instead they might shoot bursts of concentrated energy, even "hard light bullets" but not actual pieces of lead.

LOL. Not everything currently in your body is something that you necessarily need to keep in there. All those bullets you just sprayed at your opponent might just have relieved your need to hit the wash room (yeah gross, but...)