While at The Sportsmans Warehouse a couple of weeks ago, I was talking to the clerk at the pistol counter. I told him I was waiting for the MP 45 and I already had a full sized MP 40 caliber and a MP 9mm compact. He said the compact is really a sub-compact and the full sized is a compact. Is he right? If so, what is the difference between a compact and a sub-compact? :?