The .54 Renegade barrel I got a couple of months ago had a metric nipple screwed into the 1/4x28 breech plug. I didn't realize it until after my first shoot of about twenty rounds. When I went to remove the nipple to clean the gun the nipple got "wobbly" in the threads after about a half turn out. It just didn't feel right so I check the threads and found the nipple was metric. Fortunately, the threads in the plug were fine and a proper 1/4x28 nipple seated properly and tight. I called GM and almost had to force them to take down the serial number of my barrel. They posted the recall about three weeks later.