Hi Rudolph, Yes you can but just remember a steady diet of 9mm NATO ammo, or 9mm +P ammo is going to increase the wear and tear on your heater. If you’re just going to the range every now and then, it’s not going to affect you very much. However, if you’re shooting 500-1000 rounds a month, you will end up seeing internal wear quicker than you would with standard pressure ammunition.

Yes it can with no problems from what I have found they may not work with weak 9mm rounds

Rudolph, the UC-9 Fires from a closed bolt, straight blowback operation which was intended for NATO Spec ammunition from the jump. No worries firing NATO 9mm ammo here.