Armalite AR-30 muzzle brake installation

We have some pretty cool projects walk in through the shop door. A customer brought in his Savage 110 in 338 Lapua Magnum and an Armalite AR-30 tank-style muzzle brake. At first I was unsure how such a big brake would work on this rifle, but when it was finished, I learned to love it.

The rifle came equipped with the 3 chamber muzzle brake shown above. The customer wasn’t happy with how it mitigated recoil, so he purchased the AR-30 brake shown to the right. The brake includes the cast steel tank -style brake and an indexing collar. Unlike most muzzle devices which are threaded 58″-24, this one is threaded 5/8″-18.

Before we get to work, please read the following disclaimer:

The contents of are produced for informational purposes only and should be performed by competent gunsmiths only. and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.

Any modifications made to a firearm should be made by a licensed gunsmith. Failure to do so may void warranties and result in an unsafe firearm and may cause injury or death.

Modifications to a firearm may result in personal injury or death, cause the firearm to not function properly, or malfunction, and cause the firearm to become unsafe.

I ordered the following items from Brownells:

In this image you can see the side view of the brake. Note the two very large blast chambers that are angled rearwards and the blast deflector located on the rear of the brake. This is a big, heavy piece of steel.

For this project, I am using my Precision Matthews PM-1440 GT lathe with Digital Readout (DRO). We’ve been running this lathe a while and it has been the preferred tool over the other two lathes I own. You can learn more about it here.

I removed the barreled action from the stock and fed it through the head stock of the lathe. I secured it with a spider (4 screws located 90 degrees apart) on each side and dialed in the bore concentric with the lathe. For the initial dial, I am using an indicator that is reading directly off of a gauge in the bore. For subsequent readings I read directly off the bore.

I cut off the 5/8″-24 threads that were on the barrel and faced the muzzle. I didn’t save the dimensions of the shoulder for this brake and indexing collar, but I took them directly from the parts. The back shoulder is for the indexing collar to turn on, while the front tenon is for the indexing collar and brake. Keep in mind that both the brake (which is quite large) and the indexing collar are supported by these threads, so it looks a bit larger than your typical threaded muzzle.

I cut the threads using a Brownells high-speed steel insert tool. I’ve found at the lower surface speeds associated with manual lathes, the finish is superior to the carbide insert tools I use elsewhere around the shop.

With the threads finished, I came back with a triangular insert tool and cut a 45 degree shoulder behind the threads. This shoulder allows the indexing collar to snug up along the rear and match the shape on the inside of the collar.

I test fit the indexing collar (above) and the brake before I remove the barreled action from the lathe.

The finished thread and shoulder required for installation of the brake and indexing collar.

While this may be one of the biggest and loudest brakes you can buy for a gun of this size, the customer reports it works really well. He reports that it “feels like a 308 with a muzzle brake” and he “couldn’t be happier”. If nothing else, it’ll certainly get the attention of anyone shooting next to it at the range!