Keyholes and cloverleafs

Keyhole

Cloverleaf

One of the above pictures show a keyhole, another one shows a cloverleaf.

While I was in the Marine Corps, the terminology had at some point gotten mixed up. Our instructors in boot camp would call cloverleafs keyholes. I forgot about that till much later.

About two years later, one of my peers, was reading a book on aircraft maintenance. It stated that to check the barrels on the machineguns on the aircraft, you set up a plywood board and fire at it. If more than half the rounds keyholed, you would replace the barrel. This guy was astonished. He came to me and asked me why would you replace a barrel when half the rounds are going into the same hole? So I had to explain what a keyhole really is.

A keyhole is when a bullet strike the target sideways. Usually because it is unstabilized and tumbling. The top picture shows two 75 grain .223 match bullets fired out of a M16A1 barrel at 25 yards. Notice that both struck the target sideways. However both struck very close to point of aim.

A cloverleaf is where you have multiple touching impacts. The bottom target shows five 9mm rounds fired at 7 yards. The bottom cluster of three shots would be called a cloverleaf.