AR15 Anti Walk Pins Necessary?

Some users argue that anti-walk pins are unnecessary for a properly set up AR, suggesting that their need often indicates an underlying issue, such as an improperly installed trigger spring. 

However, for those with drop-in triggers, especially in cases where the trigger holes might be oversized or out of spec, anti-walk pins can be beneficial.

The best solution is to install anti walk pins, and here is why.

Why To Use Anti Walk Pins

The primary function of anti-walk pins is to secure the trigger assembly within the lower receiver, ensuring that the pins remain in place even during extensive use. One pin can't move away from the other.

KNS anti walk pins

KNS pins and Wilson Combat pins are viable options

Over time, the repetitive motion of trigger components can cause the pins to loosen and potentially slip out, especially if the trigger pin holes become elongated or "egged" in shape.

Trigger pins are generally steel, and AR15 lower receivers are mostly 7075 T6 aluminum.

Steel Pin Exerting Tension on Aluminum 

7075-T6 aluminum is known for its high strength and good fatigue strength, but it is softer and less durable than steel. Steel trigger pins are exerting tension on the aluminum, and over time these can happen:

Wear and Deformation: Over time, the harder steel pin can wear down the softer aluminum around the hole, leading to deformation. This is especially likely if the pin is subject to frequent or intense movement, which can accelerate the wear process.

Elongation of the Hole: The constant pivoting and tension exerted by the steel pin can cause the aluminum hole to elongate or become "egged," altering its original shape. This is due to the aluminum's lower hardness and strength compared to steel, making it more susceptible to deformation under stress.

Increased Friction: As the aluminum hole deforms, it can lead to increased friction between the pin and the hole. This can further exacerbate wear and may require more force for the pin to pivot, potentially affecting the performance of the mechanism that relies on this pivot action.

Galling: Galling is a form of wear caused by adhesion between sliding surfaces. Since steel and aluminum are dissimilar metals, the friction and movement can lead to small particles being torn off and welded together, causing further damage and possibly seizing the pin in place.

Drop In Trigger

For drop-in triggers including single and 2 stage triggers, designers have optimized performance by housing them within a self-contained unit, ensuring precise pin installation. This approach addresses the variability in AR15 lower receivers, where hole tolerances can differ slightly between brands. 

two stage trigger

Since trigger manufacturers cannot control these variances yet still aim to deliver consistent performance as intended, the solution is to encase the triggers in a module. This self-contained unit can then be easily inserted into any lower receiver, bypassing potential inconsistencies in the lowers' specifications.

trigger disconnector contact

Now imagine if out of spec trigger pins distance (without anti walk pins) can affect trigger pull. Yes it could slightly change how much contact surface there is.

Leave a Comment

Your email address will not be published. Required fields are marked *

Scroll to Top