Another week, another item of firearm lore to prove or disprove.... It's all in a day's work for Brownells Gun Techs Steve Ostrem and Caleb Savant, aka "The Smyth Busters"! The Myth Du Jour is this: You have to dimple your AR-15's barrel when installing the gas block. Typically used with low-profile gas blocks, the dimple is a small indentation made on the exterior of the barrel directly opposite the gas port. The dimple helps locate the setscrew during installation, and the setscrew-plus-dimple combo keeps the gas block firmly anchored so it doesn't get knocked out of alignment, which could interfere with gas flow and cause cycling problems. Dimpling is not strictly necessary, but it's helpful. Caleb admits to being a in favor of dimpling. In fact, he prefers PINNING the gas block to the barrel for even more security. He also says one dimple is better than two - and explains why. (Hint: one dimple always has to be in the same spot.) Steve has a confession, too: most of his AR-15s are not dimpled, and they shoot just fine. So this myth is BUSTED. Dimpling is NOT required, but it does provide an extra measure of security for an AR-15 gas block.