So I just finished a .450 Bushmaster build but I still need a muzzle brake. Thread size is 5/8x32 which is pretty unpopular. I've found a few but they are mostly pretty expensive and I don't need anything fancy. I had a guy lined up to make me one but he hasn't gotten back ahold of me and I'm guessing I won't be saving much going this route. So my question is can I take a meaty standard 1/2 28 and bore it out and tap it to my thread pitch?

I'm guessing this isn't something many people have done or felt the need to do but is there any reason that would be a bad idea?

It would work fine.

Most factory muzzle devices are pretty hard, so keep that in mind before you just try to run a hand tap in there.

Search "5/8-32 brake" on ebay, several generic options there.

Check with Harrells, reasonable prices and wise variety:

Harrell's Precision

Thread on his barrel is 5/8" x 32 tpi.....

I bet I have an A2 style from a .45ACP upper in my junk bin if you want to pay for some shipping.

Those are what I call Vais threads.

Not a bad option. I didn't find this one during my endless searching.

For the price I might order it and still try and mod one I have for shits and giggles

Should be no problem.

The minor diameter of a 5/8-32 is .591".

Update.. I bored it out to 19/32 however no one has this a 5/8 x 32 tap. Fastenal could order one for me for 68 bucks. Ended up ordering a tap on amazing for 30 with overnight shipping.

At this point I'll have spent as much as I would for most muzzle brakes I found but I don't care. I'm gonna take a little more pride out of my own craftsmanship and if it fails then I'll order one from Midway.

Usually people bore out brakes that are already the right thread or re thread brakes that have the desired bore. You just had to do it the hard way huh

I don't know if anyone mentioned him yet but this guy has done a ton of thread jobs including a bunch of weird brakes for people https://www.ar15.com/forums/equipment-exchange/Barrel-Threading-sale-50-PTR-91-Aug-Scar-Sig-MPX-Beretta-21A-FAL-PAPM92-Pin-and-Welds/143-1029861/

By the time I'm done I will have been further ahead having someone custome make one. But I don't care, it's a hobby so why not try something different. And later as this round and thread pitch become more popular and people are asking the same question I'll have a good answer for them.

I done messed up though. I started with a cheap brake so I'm not upset. I bored it out at work in a lathe to .593. ordered the tap off Amazon for like 30 bucks with one day shipping. But I was impatient and tapped it at home not even using a tap handle and it didn't turn out the greatest. Anyways I'm taking a new brake and my tap to work tomorrow and I'm going to do it all in the lathe this time like I should have the first time but I have complete confidence this time around.

My only thing I'm still debating is how big to make the exit hole. The brake I'm using is currently about .034 (ish if I remember right) bigger than .223. I thought about just drilling the tap drill size all the way through so I know I have plenty of clearance. Or should I do something like .490. does having a hole slightly larger than the round make a big difference in the efficiency of the brake itself?

With all of that work, I just do my own and harden them myself, I always have round steel stock around here that I can make a muzzle brake out of.

How much difference have you seen between using them annealed and hardened?

Really not much, but I am not hard on my equipment, I have a lot of guns that I can shoot, so none of them get put through the wringer, I have not fired a shot in over a month now...I am hoping to get back out in competition next year, but our season is short here for that type of stuff.

I made a couple out of 1018 that don't show any signs of wear after close to 2k rounds.   One is on a 10.5" barrel.

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One of the last times I purchased a few feet of each standard sizes, my supplier had 4140 for nearly the same price as 1018 so that is what most of my stock is now.

I made a lot out of dead soft 416 and 12L14.

Never really saw one wear out.

I've seen decent erosion on some 50 bmg guns but none were worn out.

That's usually what happens. The first couple baffles will erode a little and then it seems to stop.

Second attempt seems to be successful. I bored and drilled/tapped all on the lathe with out unchucking the brake so I feel very confident in the alignment. I bored it out to .484 so roughly .034 larger than the bullet. Most suggestions I saw said at least .02 clearance. I am slightly tempted to open it up just a little more just to play it safe but I don't want to lose any efficiency