Muzzle Brake - Mounting Depth?

[penguinofsleep]

Just got a new radial style muzzle device and when it's threaded down onto the barrel, the front end of the barrel protrudes past the very rear of the first port by about 1mm. (i.e. the first port isn't obstructed, but rather, you can barely see the barrel protruding into the port hole). If it makes a difference, port size is about 6mm, so no excessive blockage or anything.

Cosmetically, this is fine with me, but it made me wonder - generally speaking, and only generally speaking as designs vary, does the distance between the front end of the barrel and the first port of the brake matter in a way that can negatively impact anything? If it will negatively impact anything, is there any rule of thumb for how far the front end of the barrel should be from the rear of the first port? Or is it just kind of a guess and check kind of thing?

 

[E. Bryant]

My concern wouldn't be brake performance, but rather that those threads will eventually get loaded with carbon and other combustion by-products, and make the brake a real SOB to remove later. Put a precision shim between the barrel and brake.

 

[iceng]

It's not detrimental to performance, but it will make life hard eventually.

 

[penguinofsleep]

@iceng - Could you clarify? Or is your recommendation the same thing with the shims?

 

[iceng]

Sure. Having your muzzle, or crown extend into the muzzle brake, to the point where you can see the thread of your barrel, will NOT be harmful (all things being equal and correctly aligned), however if and when you want to unscrew the brake, you will have threads with solid carbon chunks, and that will fight you like an angry crab with extreme prejudice.

Having some shims to ensure the muzzle brake is covering all your barrel / muzzle thread, you won't need to fight it as hard to remove it.

Short version is "I recommend using shims, else it's gonna be a shit fight to remove, but doesn't doesn't cause any accuracy or recoil loss that I've found".

 

[viking78]

Talking about the muzzle brakes.
This new (2021) from Browning looks nice, easy to mount and remove.

Recoil Hawg Muzzle Brake Introduction - Browning

One of the most effective rifle muzzle brakes in the industry. The Recoil Hawg devours felt recoil and muzzle jump — proven to reduce recoil up to 76%.

www.browning.com

 

[iceng]

Really interesting way of attaching for self timing. I love innovations like that.

 

[Yondering]

Hey OP - something I'd be wondering is "why" the barrel protrudes into the port. It sounds like you might be using a muzzle device made for either 9mm or 22 LR on a 5.56? All three of those use 1/2"-28 threads, but the standard thread lengths are different. 5.56 barrels will usually use a .620" threaded section, 9mm is ~.500", and 22 LR will usually be either .400" or .500" depending on who's spec you use.

So if you use a muzzle device with a .500" thread length on a 5.56 barrel, yeah you'll have some compatibility issues. I'd also be concerned whether the muzzle device is actually stopping against the barrel shoulder, or something else. Binding on the threads for example, or on the small unthreaded section against the shoulder (depending on your 5.56 barrel), or even on the corner of the shoulder instead of the face.

 

[iceng]

Pro tip. Thread diameter is usually thread length. Not exactly, but a good starting point.

Core of the thread diameter should be the minimum length of the thread, this gives the thread better yield strength for snapping.

Paging @308pirate . He can give the specifics and clarify if I am wrong. He might sniff butts and be out on bail, but he knows his shit.

 

[spife7980]

Got pics? I’d assume it’s so that the brake doesn’t develop carbon build up that might encroach on the bullets travel and is set up as intended. 1mm won’t be so many threads that it really gets locked on there.

 

[E. Bryant]

Pro tip. Thread diameter is usually thread length. Not exactly, but a good starting point.

Core of the thread diameter should be the minimum length of the thread, this gives the thread better yield strength for snapping.

Paging @308pirate . He can give the specifics and clarify if I am wrong. He might sniff butts and be out on bail, but he knows his shit.

There is some mildly-fancy math that should be done to ensure that the shear strength of the thread profile matches the tensile strength of the minor diameter. Or just use one of those rules-of-thumb and get close enough for standard fasteners. Torque-to-yield stuff requires a sharper pencil.

 

[Yondering]

Pro tip. Thread diameter is usually thread length. Not exactly, but a good starting point.

Core of the thread diameter should be the minimum length of the thread, this gives the thread better yield strength for snapping.

Paging @308pirate . He can give the specifics and clarify if I am wrong. He might sniff butts and be out on bail, but he knows his shit.

No, not really. We’re talking about muzzle threads here, not nuts and bolts which get torqued a lot higher.

I’ve threaded a lot of barrels, using specs from Silencerco, Thunderbeast, Gemtech, etc, and the thread lengths I specified above are accurate to industry accepted standards.

Besides, the issue is not about whether the OP has enough threads for strength. That’s not a problem. The issues are what I described above.

 

[penguinofsleep]

Sure. Having your muzzle, or crown extend into the muzzle brake, to the point where you can see the thread of your barrel, will NOT be harmful (all things being equal and correctly aligned), however if and when you want to unscrew the brake, you will have threads with solid carbon chunks, and that will fight you like an angry crab with extreme prejudice.

Having some shims to ensure the muzzle brake is covering all your barrel / muzzle thread, you won't need to fight it as hard to remove it.

Short version is "I recommend using shims, else it's gonna be a shit fight to remove, but doesn't doesn't cause any accuracy or recoil loss that I've found".

Makes perfect sense. I figured 5/8 x 24" threads with 1mm protrusion wouldn't be "that much" carbon to "get it stuck". But yeah, you guys are right - what's the cost of a shim vs the extra effort it will take to get it off. Barrel is cerakoted and brake is some kind of bluing I think - just need to find a shim that is dark-ish colored.

As for thread engagement - I have at least a 1/2" of thread engagement from the shoulder to the tip of the barrel - should be more than enough with 5/8 x 24" threads. Barrel protrudes into the brake just because shoulder to tip is "that much longer" than the average hunting barrel that I've seen (granted, not a ton, so maybe I'm wrong) and there's no internal shoulder inside of the brake. It is a brake meant for hunting cartridges ~243 - 30 or 338 cal though - they did double check caliber, barrel diameter at end, etc. with me before machining it for me.

 

[Yondering]

Makes perfect sense. I figured 5/8 x 24" threads with 1mm protrusion wouldn't be "that much" carbon to "get it stuck". But yeah, you guys are right - what's the cost of a shim vs the extra effort it will take to get it off. Barrel is cerakoted and brake is some kind of bluing I think - just need to find a shim that is dark-ish colored.

As for thread engagement - I have at least a 1/2" of thread engagement from the shoulder to the tip of the barrel - should be more than enough with 5/8 x 24" threads. Barrel protrudes into the brake just because shoulder to tip is "that much longer" than the average hunting barrel that I've seen (granted, not a ton, so maybe I'm wrong) and there's no internal shoulder inside of the brake. It is a brake meant for hunting cartridges ~243 - 30 or 338 cal though - they did double check caliber, barrel diameter at end, etc. with me before machining it for me.

5/8-24 threads are typically .620-.625” long. Sounds like your brake is shorter than that, but if it was made for hunting barrels, I’ve seen all sorts of non-standard thread dimensions on hunting rifles especially if it was made or cut by a smith not familiar with modern standards.