AR Recoil Buffer Spacers

This project provides different sizes and types of spring spacers for the recoil system in AR platform firearms. These should work in any AR style firearm that uses a standard recoil tube with a 1" inside diameter.

Purpose

On some AR-platform firearms the bolt travels "too far" past the bolt catch. This can be "by design" (e.g. using a regular carbine buffer in a 9mm build) or due to parts not quite matching (e.g. ar-10/lr308). A common fix for this is to put a stack of quarters or a block of delrin behind the recoil spring to limit buffer travel. This adds preload to the spring in addition to providing a spacer for the buffer, which may or may not be what you want.

The straight spacers here will help you adjust buffer travel and also change spring preload. The stepped spacers will help you adjust buffer travel without significantly changing preload.

Spacers

The straight spacer is 0.995" diameter along the entire depth and will preload the spring.

The stepped spacers start at 0.995" diameter, and step down to 0.785" for an interference fit inside the spring (may not fit inside flat wire springs).

All spacers have a 3/16" hole in the middle.

• Stepped spacer 3/16" deep
  • 1/16" thick shoulder
• Solid spacer 1/4" deep
  • You can scale this in the Z axis only for any depth you want and it will also preload the spring
  • Use this for spacers less than 3/16" thick
• Stepped spacers for depths 1/4" to 1", in 1/8" increments
  • 1/8" thick shoulder
  • If you need a spacer in between sizes, pick the closest size and scale the model in the Z axis only to the appropriate depth
  • Stepped spacers over 1/4" deep have a 1/8" radius on the narrow end, and step down an additional .020 past 1/4" to make it easier for the spring to compress over the spacer.

Files

The naming convention for the files is:

`spacer-