What barrel thread spec for .820” .458?

[Orr89rocz]

Wanting to put a muzzle brake on a .458 cal rifle, win mag. Barrel is .820” diam at muzzle. Is this enough for a 3/4-24? I’ve heard .050” of shoulder so do i look at major thread diam when considering this? Or minor?
Whats a min barrel wall thickness i need to maintain?
Thanks

 

[tobnpr]

Major is for your shoulder, you're a bit skinny IMO- you'll have at most .035 or so shoulder and will be less depending on concentricity of the bore to the barrel OD. I wouldn't mount a suppressor with that small a shoulder, but it should be OK for a brake if you go light on the torque relying on the shoulders for alignment and use some Rocksett or loctite so as not to deform/crush the shoulder.

Minor diameter is for your barrel wall thickness, where you want at least .100.
Your minor is about .700, so you'll have about .120 barrel wall thickness which is fine.

It'll work, but like I said the barrel shoulder is on the skinny side...

 

[DaveTooley]

This ^^^^^^^^^

 

[WSnyder]

Is this enough for a 3/4-24?

You want 11/16-24. Hankins and Harrells both make them in this thread pattern. There may be others.

 

[Orr89rocz]

Thanks all!

 

[ronemus]

You could use a self-timing brake so a shoulder is unnecessary. I would prefer 3/4"-24 for a .458.

 

[Sniperhandle]

You can also shoulder it inside the brake touching up against the muzzle, Some guys have done this and it works fine.

 

[jackieschmidt]

You could use a self-timing brake so a shoulder is unnecessary. I would prefer 3/4"-24 for a .458.

A self timing muzzle brake has to have an even harder shoulder, as the jam nut thread is actually larger than the internal muzzle brake thread.

 

[ronemus]

A self timing muzzle brake has to have an even harder shoulder, as the jam nut thread is actually larger than the internal muzzle brake thread.

In at least some designs, the jam nut runs up against the brake - no shoulder needed.

 

[jackieschmidt]

In at least some designs, the jam nut runs up against the brake - no shoulder needed.

True. That’s probably his best option.

 

[ELR LVR]

In at least some designs, the jam nut runs up against the brake - no shoulder needed.

This ^^^
A Jam nut needs no shoulder to butt up against
You can machine your own custom jam nut/shoulder too, contour it, give it some nice lines, etc

 

[LVLAaron]

Plenty of 45 cal brakes out there that are 11/16 thread.

 

[tobnpr]

In at least some designs, the jam nut runs up against the brake - no shoulder needed.

So this is a new one on me...I've never heard of a jam nut being used to time a brake.
Goes against a basic principle, which is that threads bring the parts together- but the shoulders are what perfectly align them.

There must be runout using this method, has anyone ever measured it?

 

[WSnyder]

So this is a new one on me...I've never heard of a jam nut being used to time a brake.

There is and has been a huge plethora of self timing brakes using one form or another of jam nut out there. APA, Area 429 (uses an internal taper for alignment), Hankins, PVA and many more..... None of them have any appreciable runout or enough that they don't work properly.

 

[WSnyder]

A Jam nut needs no shoulder to butt up against

Some of the self timing brake's out there do require a shoulder.

 

[jackieschmidt]

Some of the self timing brake's out there do require a shoulder.

The one I put on my ELR build, the Big Bastard, uses that.

 

[tobnpr]

There is and has been a huge plethora of self timing brakes using one form or another of jam nut out there. APA, Area 429 (uses an internal taper for alignment), Hankins, PVA and many more..... None of them have any appreciable runout or enough that they don't work properly.

The lock nuts index against the barrel shoulder.
From APA's installation instructions:

If your shoulder is not square or of sufficient diameter for your barrel you may require purple or blue Loctite on your barrel threads only to hold the brake in place.

That said, it seems to indicate that you can rely on loctite same as I mentioned above even with an out of square shoulder. I'm cool with the shoulders aligning, but I'm just not with a nut on a threaded rod and expecting precise concentricity. JMO.

 

[LVLAaron]

They have two sets of threads. They work great.

 

[ELR LVR]

Some of the self timing brake's out there do require a shoulder.

I use Jam nuts for most of my brakes
none of them touch the shoulder
this is the easiest way for me to index them straight
-------------
I don't own any self timing models so cannot comment on that

 

[Sniperhandle]

They have two sets of threads. They work great.

View attachment 1652998
View attachment 1652999

I found one just like that 40 yards out from the Bench I was shooting on, It's a Gen 2 or something like that Fat Bastard brake as far as I can tell. I put it on my 300 PRC build I did. I was walking to my target and saw it laying there, In good shape too, I just had to get the piece of broke off barrel that was loctited in out of it. True story.
This is the one.