"You have to pin the gas block or else!" say a lot of serious AR-15 builders, the "or else" being that the block will work loose and your rifle will malfunction. Nowadays, there are gas blocks that clamp on or are secured by setscrews, so we asked Brownells Gun Techs™ Steve and Caleb if pinning is absolutely necessary. The original AR-15 / M16 design called for the gas block to be pinned, and that's still the most SECURE, most durable method. But the other attachment methods make it a lot easier to install or change the gas block. If you want a pinned gas block and don't want to do machining, you have to buy a barrel with the gas block already installed. Setscrew and clamp-on gas blocks are great for the home "hobbyist" AR-15 builder, especially low-profile gas blocks that will be protected by the handguard. If you're like Caleb and want your AR-15 to last through the Apocalypse, pinning is the way to go. The Smyth Busters are split on this one: Steve says the gas block doesn't always have to be pinned, Caleb says it does. What do YOU think? Tell us in the comments below!