AR Buffer Spacer

thingiverse

# 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. ## 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-<adjective>-####.stl` where: `<adjective>` = whether the spacer is stepped or straight `####` = the depth of the spacer in thousandths of an inch, truncated to 4 places. e.g. 1000 = 1 inch. 0250 = 1/4 inch. etc. ## Scaling This is done in the slicer. I'm including a screenshot of what this looks like in Cura. The key is to only scale in the Z axis, so you may need to uncheck a box that links scaling across the axes. ## Notes Twist opposite the wind of the spring when installing the spacer--this opens the coils and makes it easier it insert. These may not fit in flat wire springs (I may work on separate models for those, but I am not sure if the ID is as consistent since they are not mil-spec).