Big cartridges invite big mistakes, mostly because many of them share a bullet diameter or a similar name, and even the humble .22 LR has its traps. These eight come up most often. 1. Mixing the .450s The .450 Bushmaster, the .450 Marlin and the .450 Nitro Express are three different cartridges. The Bushmaster is a straight-wall AR-pattern cartridge with a .452-inch bullet, the Marlin a belted...