What Is an AR15 Buffer? 

An AR-15 buffer is a crucial component of the rifle's recoil system, working in conjunction with the buffer spring to manage recoil and cycle the action. It's a cylindrical part that slides within the buffer tube and absorbs the impact of the bolt carrier group when the rifle is fired. The moving weights inside the buffer perform the “deadblow” effect to help keep the bolt carrier group from bouncing after it closes on the chamber. Without the proper dead blow effect, the bolt carrier group can bounce, which affects cycling and lock time. Different buffer weights are available, each affecting how the rifle cycles and manages recoil. 

What Does a Buffer Do?

The buffer's primary job is to slow down the bolt carrier group (BCG) as it travels backward after firing, preventing it from slamming into the end of the buffer tube. It also helps stabilize and dampen the bolt carrier from bouncing as it moves forward to close on the action during the cycling process. The buffer and buffer spring also keep the BCG closed with a preload tension, preventing the bolt from coming unlocked while it is being transported or fielded.

How Does a Buffer Work?

When the rifle is fired, gas pressure forces the BCG backward. The buffer, which is located in the buffer tube, absorbs some of this force. As the BCG moves backwards, the Buffer also moves backwards while compressing the buffer spring. The Buffer then finally slows down the BCG from its rearward movement, and the stored energy in the buffer spring pushes the buffer, and therefore the complete BCG, forward again, stripping a new round from the magazine and chambering it. 

What Is a Buffer Tube? 

The buffer tube, which houses the buffer and spring, is also a critical part of the recoil system and comes in various sizes and configurations (Pistol Buffer Tube, Mil-Spec Buffer Tube, A5 Buffer Tube, Rifle Buffer Tube, etc). 

Buffer Weights

AR-15 buffers come in different weights. Heavier buffers generally reduce felt recoil and can improve reliability with certain ammunition types or when using a suppressor. Lighter buffers may be preferred for faster cycling or in specific configurations, but can increase felt recoil and potentially lead to reliability issues. 

• Carbine Buffer — 3 oz.

• Heavy (H) Buffer — 3.8 oz.

• H2 Buffer — 4.6–4.7 oz.

• H3 Buffer — 5.0–5.4 oz.

• 9mm Blow Back Pistol Buffer — 5.0–8.5 oz. and Heavier

Choosing the Right Buffer

Selecting the appropriate buffer weight depends on factors like barrel length, gas system, ammunition type, and whether a suppressor is used. Using a heavier buffer weight increases resistance for the BCG moving backwards, resulting in smoother operation and reduced felt recoil. 

However, if the buffer is too heavy, it can hinder the rifle's cycling, causing issues with extraction and ejection. A practical guideline is to select a buffer weight that consistently allows your rifle to lock back when the magazine is empty. Try loading a single round and verify that the rifle locks back multiple times consecutively.