I work part time in a gun shop and Haz would go crazy with what I hear multiple times a day. I would guess that 85% of the people coming in the shop call an ammunition magazine a (brace yourself Haz) "clip." So when I hear a customer misuse the term, "Hey, do you have any clips for a Beretta?" I respond back with, "We have magazines over in this cabinet, lets take a look."
Another good one is, "How many 'bullets' does the 'clip' hold?"
My response is (in the case of an XDm 9mm), "The magazine holds 19 cartridges of 9mm."