How to Blend a JP Comp

By Kevin Muramatsu

The Process

Step 1: Timing the Compensator

The first step for a beautiful barrel is to perfectly time the comp.

An AR barrel's thread shoulder is typically cut back to where the compensator will tighten down and maintain proper alignment. In other words, the little holes on the top of the JP comp should be exactly at the 12:00 position on the barrel.

If this isn't the case, you'll need to contact a suitable gunsmith to have your comp. properly timed before proceeding. Nothing will bother you more than looking at your comp. improperly clocked on your barrel.

Step 2: Sanding

At this point, your barrel will typically be in a rough-turned state from the barrel supplier. The comp will be in a well-polished state from the beginning. This will leave a small step and an obvious transition between the comp and the barrel.

Begin sanding this intersection with a low-grit abrasive to roughly remove the intersection. Make sure to keep the abrasive moving from side to side to avoid misshaping the barrel. Then, you'll sand the entire assembly with progressively higher grit abrasive until the surface reaches your desired appearance.

Typically, we would start on the transition area with 180 grit abrasive. Then, the entire barrel would get 240 grit, followed by 320 grit and then 400 grit.

Step 3: Final Blending

The final step is to sand with a black Scotchbrite abrasive pad. In this case, the comp is given the same treatment so that it has the same external appearance as the barrel.

This process completely removes the evidence of the intersection between barrel and comp while bring the steel of both to a uniform surface finish. The result is the appearance of a one piece barrel/comp.

So, there you have it—the insider secret to a gorgeous JP-style barrel.

About the author:
Kevin Muramatsu is a certified gunsmith and current gunsmithing instructor. He is author of numerous books and articles on firearm maintenance, history and customization, including The Gun Digest Guide to Customizing Your AR-15. Former lead gunsmith for JP Enterprises, Kevin now owns and operates his own custom shop, Village Pine Custom.