Smyth Busters: Does Every AR-15 Need an Adjustable Gas Block?

One of the most popular AR-15 upgrades in recent years has been the adjustable gas block. It's so popular, some folks now insist that every AR-15 should have one. But is that true? Brownells Gun Techs™ Caleb and Steve say there are situations where an adjustable gas block is useful, but it's NOT a cure for every gas system problem. Scenario: your AR is under-gassed - doesn't have enough gas flow to cycle the action reliably. Will an adjustable gas block let you "dial up" more gas to fix it? Nope. When you fire a shot, a little gas exits the barrel through a port under the gas block. The gas block's corresponding port is LARGER than the one in the barrel. An adjustable block can only RESTRICT gas flow; it can't draw MORE gas from the barrel because that's limited by the barrel's gas port. This will not help an under-gassed AR-15! Manufacturers often over-gas their guns to ensure reliable cycling. You may actually need to reduce the gas flow, and an adjustable gas block is the way to go. You could also install a heavier buffer to counteract the excess gas, but Caleb explains why an adjustable gas block is the better solution. Steve likes to dial down the gas flow on AR-308s to make 'em shoot softer. So the myth is half-busted: You don't always need an adjustable gas block, but it can be very useful on an over-gassed AR-15.