Smyth Busters: Does Your AR-15 Need Anti-Walk Pins?

Caleb has been at it again! He went on the Internet forums and social media groups and found a whole lot of controversy over AR-15 anti-walk / anti-rotation pins versus the standard hammer and trigger pins. Some folks are pro-anti-rotation pins. Others say anti-rotation pins are a terrible idea and are pro-standard pins..... so they're anti anti-rotation pins! This causes lots of confusion for AR-15 owners who just want to make sure they have the right pins in their guns. Caleb is joined by his fellow Brownells Gun Tech™ Steve, so they can settle the Great AR-15 Hammer and Trigger Pin Controversy once and for all.

 

WHAT THEY DO: "Anti-walk" and "anti-rotation" pins are different and do two different things. First, let's get clear on what the standard hammer and trigger pins do. Two types of fire control group (FCG) are commonly used in the AR-15 platform. The traditional "mil-spec" FCG - trigger, hammer, disconnector, and accompanying springs - is held in place in the lower receiver by a pair of pins, one going through the hammer, the other through the trigger. The pins are locked in the receiver by the legs of the hammer spring. Everything you need to keep that FCG securely anchored in the rifle is actually part of the FCG.

 

Self-contained, drop-in, cassette-type trigger modules - such as those by CMC Triggers, Elftmann, Rise Armament, Timney, Wilson Combat, and other manufacturers - lack the standard hammer spring to retain the standard pins. These FCGs REQUIRE anti-walk pins, which lock in place and won't work their way out ("walk") over time as you cycle the trigger.

 

SPIN ME ROUND, BABY: Anti-rotation pins serve a different purpose. They have a little steel bridge on the outside of the receiver that keeps the pins from spinning in the receiver holes. The theory is that over thousands of rounds fired, the rotation of the pins wears the receiver holes, making them bigger, which will eventually let the pins fall out. Except..... that really doesn't happen. Using the wrong tools to remove the pins during maintenance can damage the holes and cause them to open up. Anti-rotation pins are a solution to a problem typically caused by "operator error." The non-rotation of the pins will slow lock time.

 

A DIFFERENT PROBLEM: Some folks switch to anti-walk or anti-rotation pins because they have trouble with the standard pins breaking. "That's not a pin problem," says Caleb, "that's a firearm problem." You need to decrease the gas flow or increase buffer weight because the bolt is moving way too fast and hitting the hammer way too hard. The weakest link breaks first, usually the hammer pin.

 

UH-OH: What if you have the wrong pins in your AR-15 right now? You'd probably have to put a HUGE number of rounds through the gun before you have problems. We're mostly talking about optimization and minimizing risk here. But at some point, it's a good idea to swap in the correct pins.