AR-15 - How To Dimple Your Barrel

Looking to try some DIY gunsmithing? Making changes to your expensive AR-15 components, such as using a drill to drill into your brand new barrel, can be intimidating. Then this how to should help alleviate some of that worry. I had a low profile gas block that I wanted to install on my AR-15 barrel but my barrel did not have the appropriate dimples for the gas block’s set screws to sit in. I like to try new things so I decided to go for it and record a video of the process at the same time. Allow me to walk you through the steps I took, and we’ll work through this home gunsmithing together. It may be easier than you think. If I can do it, you can, too.

Disclaimer: This tutorial is to show you step-by-step one procedure to dimple your barrel. I, nor The Arms Guide, assume any responsibility for any harm to person or property that may occur during your efforts when you try this for yourself. Be careful, folks!

Tools Needed

Hand held drill or drill press.
Center punch.
7/64″ drill bit.
11/64″ drill bit.
Bench vise.
Wood pieces or soft jaws.

This shows how I placed the pencil line from the center of the gas port down the barrel.

Look closely and you will see the pencil line I placed down the center of the gas block.

Alignment

First and foremost, you will want to know where to place the dimples in your barrel, right? Since we will be using the gas block to help us line everything up, be sure to utilize the gas block that you will ultimately be installing. This will help make sure that the dimples are drilled correctly. For a visual on the installation process, watch this video. Here is the quick and dirty:

Using a pencil, make a line down the center of your gas port. Continue it down the barrel a couple of inches. I recommend using a straight edge for this.
On the face of the gas block, agin using a pencil, draw a line down the center of the face of where the gas tube installs.
Slide the gas block into position over the gas port leaving about a thumbnail’s thickness (about 1/16″) space from the barrel’s shoulder.
Looking at the front of the gas block, line up the gas block pencil mark to match the one you drew on the barrel.

Now that you have followed the steps above and your gas block is properly aligned with the gas port, we need to mark where to drill the dimples. There are several approaches to this, but here is the method I used. I simply tightened the set screws enough to leave a mark on the barrel. This method allowed me to ensure my pencil lines were straight while tightening the screws, therefore marking the barrel exactly where I wanted the dimples.

Here you can see the markings left behind from the set screws. This is where I will be drilling the dimples.

Drilling

Nervous? I was too, but there’s no need to be. Remember: if I can do it so can you. Be safe and go slow, and you should be just fine. Moving on. Place your barrel into the wood pieces (or soft jaws) in the vise and clamp it down snugly. You should not be able to move your barrel at all once you’ve tightened down the vice. Make sure that the barrel is rotated so that the dimple markings you made are facing upward as straight as possible.

One thing we want to avoid is for the drill bit to start “walking.” We’re going to be drilling on a rounded surface, so we’ll first have to give the drill bit something to “bite” into. Using the center punch, punch a spot in the center of each dimple mark.

These are what the 7/64″ dimples should look like before moving onto the larger 11/64″ drill bit.

Instead of going right to the 11/64″ drill bit, start with the 7/64″ drill bit. Again, going slow is important, and this is insurance to avoid the drill bit moving around and scratching up your barrel. Begin drilling once the drill bit is centered in the small indent you created with the center punch. Going at a slow speed, you will want to keep the drill as straight and level as possible. Continue to drill both marked areas with the 7/64″ drill bit until you have are two small dimples.

Replace the 7/64″ drill bit with the larger 11/64″ drill bit and repeat the process as before, remembering to take your time and be careful. The dimple will be the right size once it is the same diameter as the 11/64″ drill bit.

The final 11/64″ dimples should look like this.

Installing the Gas Block

Those are some nice looking dimples, if I do say so myself. As you can see they are placed right where the set screws will screw into the gas block.

Congratulations, you just successfully dimpled your barrel. Let’s celebrate by installing the [low profile] gas block. Make sure that the set screws are out far enough to allow it to freely slide over the barrel and into place. Once you have the gas block in place, remove one of the set screws completely and take a peek through the hole. You should see your freshly drilled dimple looking back at you. Go ahead and screw both set screws in tightly with some thread locking agent. You now have a properly mounted set screw style gas block that will not rotate because you dimpled you barrel. That wasn’t too bad at all, was it?