Minimum Barrel Shoulder?

[Lonewolf74]

I'm looking to find out what is the guidelines or recommendations on the minimum amount of shoulder left on a barrel after threading it for a brake or suppressor?

For example if the finished diameter of the barrel is .830 and you thread it 3/4-24 there will be approx .04 shoulder left for the brake to seat against. Is this enough or should there be more and do you have any rule of thumb to follow?

Your help is appreciated guy's
Joshua

 

[tobnpr]

I like .100, have done as little as .025 with caveats...
In your example, the .040 is in a perfect world- depending on the barrel, it will be less on one side and more on the other. Match grade barrels will be pretty close, low-tier commercial barrels could have a bore that's off by five or ten thousandths from center of OD.

Really "depends".

For me, using Rocksett is a substitute for torque- to a point.
Shoulders align the parts for perfect concentricity; if I've got to deal with a less than optimal shoulder I use less torque to avoid damaging the small surface area and rely on Rocksett to hold that positioning and not allow the brake to vibrate loose.

Also- big difference between a brake that might extend an inch, or two from the muzzle- and an 8" or 10" suppressor in terms of the potential for bullet strikes. I'd do a short brake at .040, but not a suppressor.

 

[bpctcb]

I look for a proper shoulder to be 0.10" larger diameter than my threads.

I recently cut down and threaded my 700 BDL in 300 mag. There wasn't enough barrel for a suitable shoulder for my suppressor to mate against. My solution was to install a jam nut tightened hard onto the barrel then face it off to act as the shoulder. Works perfect.

BP

 

[Lonewolf74]

Thanks for the help guy's. I'm really asking this to determine what thread size brake to order for some current builds. Both will be match grade barrels one will finish at .830 the other will be about .865 at the muzzle. So with both of these you guy's would recommend going to 5/8 and not 3/4 on thread size?

I really wanted to go 3/4 just cus in my mind the less material is removed from the barrel the better but maybe it doesn't matter much?

 

[Another Casual]

Some silencer manufacturers publish their thread specs. Thunderbeast requires the below minimums:

Thunder Beast Arms Corporation [TBAC] | Tech | THREAD SPECIFICATIONS

 

[bpctcb]

Thanks for the help guy's. I'm really asking this to determine what thread size brake to order for some current builds. Both will be match grade barrels one will finish at .830 the other will be about .865 at the muzzle. So with both of these you guy's would recommend going to 5/8 and not 3/4 on thread size?

I really wanted to go 3/4 just cus in my mind the less material is removed from the barrel the better but maybe it doesn't matter much?

I see what you're saying where. Kinda depends on the barrel's bore diameter. I would use 5/8-24 unless you've got a bore larger than .308.
There are brakes available in 11/16-24 also.
BP

 

[Lonewolf74]

I see what you're saying where. Kinda depends on the barrel's bore diameter. I would use 5/8-24 unless you've got a bore larger than .308.
There are brakes available in 11/16-24 also.
BP

The barrel that will finish about .830 will be .308 caliber the barrel that will finish between .860-.870 will be .338 caliber. I'm set on using the TI pro 3 brakes from livetohunt and I'll see if he offers 11/16-24.

So if I can't get 11/16 would you then go 3/4 for the 338?

Thanks again for the help guy's
Joshua

 

[bpctcb]

The barrel that will finish about .830 will be .308 caliber the barrel that will finish between .860-.870 will be .338 caliber. I'm set on using the TI pro 3 brakes from livetohunt and I'll see if he offers 11/16-24.

So if I can't get 11/16 would you then go 3/4 for the 338?

Thanks again for the help guy's
Joshua

Yes, I would go 3/4 for the larger 338 barrel.

 

[tobnpr]

Edit

 

[tobnpr]

So if I can't get 11/16 would you then go 3/4 for the 338?

5/8"-24 minor diameter is .575
Still .118 or so barrel wall thickness with .338 which is perfectly fine.
This would be my preference over the .055 or so shoulder you'd have with the 3/4" brake; next size down provides more shoulder area and adequate barrel wall thickness.

JMO, YMMV.

 

[Lonewolf74]

5/8"-24 minor diameter is .575
Still .118 or so barrel wall thickness with .338 which is perfectly fine.
This would be my preference over the .055 or so shoulder you'd have with the 3/4" brake; next size down provides more shoulder area and adequate barrel wall thickness.

JMO, YMMV.

J E Custom has a guide line of having a minimum of .150 of barrel wall thickness especially on the more intense cartridges. I respect his opinion immensely and my build is going to be a 338 Norma mag improved so I'll definitely error on the side of caution. I just couldn't find much on what ppl recommend for a minimum shoulder amount, however going back and reading some of J E's stuff I see where he wants a minimum of .025 for a shoulder so I should be more than good going 3/4 in the 338 barrel.

Thanks again for the help and getting this sorted out guy's!
Joshua

 

[jrock]

I recently made some phone calls to a couple barrel and suppressor manuf. The barrel guys told me to talk to the suppressor guys. The suppressor guys gave 0.05" minimum to 0.1" recommended but then said its really a question for a machinist.

I have a 338 Norma Mag stainless barrel with a 0.76" muzzle threaded 5/8x24.