Many people select defensive ammunition without considering what kind of flash comes out the end of the barrel when it's fired, even though we know that most civilian self-defense situations happen in low-light or no-light circumstances. In this month's Equipment Review, we'll take a look at the types of muzzle flashes that some of the most common ammunition puts out through a full-size 9mm handgun, compact 9mm handgun, full-size .45ACP handgun, and M4/AR-15.