15 fold

An assault rifle usually a "Armalite Rifle" or "AR-15" with some sort of foldable stock.

"15 fold" the 15 coming from the rifles name in "AR-15" and fold coming from the attached foldable stock or the fact the victim will probably fold after the AR-15 is brought out.
"This foo better watch out before I whip this 15 fold on his goofy ass"