Custom Muzzle Break for my bench AR.

So I was cleaning out my shops stock shelves and discovered we have a bunch of 416 stainless bar stock. I wanna make a long custom muzzle break for my bench AR. Its 5.56/.223 but will likely be a .223 wylde barrel. What is the minimum reamed hole I need for the bullet to clear the inside of the muzzle break. The break will be a square break about 4.5" long. Is .250" too big?

nissan300ztt said:

Is .250" too big?

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The short answer is both yes and no. No more than .020" over has proven to be optimum. So .244" would be where I limit it. However, that would be in a perfect world with a perfect design... If you drilled the bore to 15/64 then ream to .250" I can't see it be an issue in the real world.

My understanding is that the smaller the bullet exit hole, the more effective the brake will be.
Ideally, just large enough to let the bullet pass without touching.
The problem with commercial brakes is that they have to work on barrels whose bores are not concentric.
I would probably adjust the barrel in a 4 jaw chuck so that the bore was centered instead of the barrel.
Then thread the barrel and install the nearly completed brake.
Index it like you would a barrel in a receiver, and then drill the bullet hole from the tailstock.
Check alignment with a range rod before shooting.

The best way to cut the threads for a muzzle break is between centers on a lathe. Actually it is the only truly correct way.

You want minimum .020 over bullet diameter.
My experience is that overbore isn't as critical to performance as some think.
Plenty of suppressors are used universally to fit .22 cal and .30 cal. without significant loss of performance.

If muzzle work (crowning) is done through the headstock, I fit the brake to the muzzle after threading, make a light cut with a boring bar to assure the drill bit (and after, reamers) is following a concentric hole. All done in the same setup.

If the muzzle work is done between centers, it may be "technically" not as precise as you can't assure perfect concentricity in a single setup. I drill/ream the brake to size in a collet. Any from a reputable manufacturer will have the threads and center hole concentric to the OD of the brake, and I've never had a problem doing it this way, either.

Never had the bug to want to machine my own from scratch, can be bought much cheaper than I can make one...

If going down that road, this would be a good read, and they make "blanks" to save some work if you just want to experiment with DIY porting:

The Accurate Muzzle Brake Book – Newlon Precision

that’s what I do drill thread and exit hole from rear one set up
Don


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I ran a brake on the LR-10 for a couple sessions. The guys at the benches on either side just about threw me off the range ;-)

Now I run a Blast Forwarding Device. BFD! ;-)

Looks like everyones making muzzle brake a these days.

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