View Full Version : Muzzle device sitting on muzzle instead of barrel shoulder
I recall reading a thread talking about this a long time ago, I've been searching for a while without finding it so here goes.
Specifically talking flash hiders that do not need to be indexed, like AAC blackouts, NOT suppressor-bearing hiders, is it considered acceptable to install one without crush or peel washers and simply torque it down on the face of the barrel, that is, the hider is sitting on the face of the muzzle instead of the shoulder of the barrel behind the threads? Meaning the muzzle device does not contact the shoulder of the barrel at all.
Knowing many barrel designs simply don't have a shoulder (or too small of a shoulder) to hold a washer/muzzle device due to their small diameter, I'd be inclined to think this would be fine.
However has anyone found detriments towards accuracy and/or strenght of using this method?
I would not be comfortable tightening a muzzle device against the muzzle. I'd be worried it would distort the crown.
Chris Bonesteel
10-03-18, 14:19
Assuming the crown is cut square to the bore, i cant see it causing any issues. Assuming that the flash hider in question also has a face in the proper position that is also square.
I recall reading a thread talking about this a long time ago, I've been searching for a while without finding it so here goes.
Specifically talking flash hiders that do not need to be indexed, like AAC blackouts, NOT suppressor-bearing hiders, is it considered acceptable to install one without crush or peel washers and simply torque it down on the face of the barrel, that is, the hider is sitting on the face of the muzzle instead of the shoulder of the barrel behind the threads? Meaning the muzzle device does not contact the shoulder of the barrel at all.
Knowing many barrel designs simply don't have a shoulder (or too small of a shoulder) to hold a washer/muzzle device due to their small diameter, I'd be inclined to think this would be fine.
However has anyone found detriments towards accuracy and/or strenght of using this method?
Where are you seeing skinny barrels without shoulders? I have never seen one. I have never seen an AR barrel less than .625 diameter and all had shoulders much larger than .625. Even if you cut the shoulder off and rethreaded the muzzle you would still have a shoulder big enough to support a PA shim. The ID of PA shims is only a few thousands larger than the major thread diameter. Assuming a standard 1/2-28 thread is used. I am not sure I have ever seen a flash hider that wasn't bored more than an eighth deeper than the threads. What would the muzzle bottom out on? The threads crashing on each other??
Jwknutson17
10-03-18, 15:06
Knights SR25 guns index off of the muzzle of the barrel. They do not have a shoulder to index / time off of. It is all done on the muzzle of the barrel. This method has never been an issue.
Surefire muzzle devices come with instructions for timing off the muzzle vs. a shoulder.
Assuming the crown is cut square to the bore, i cant see it causing any issues. Assuming that the flash hider in question also has a face in the proper position that is also square.
THIS ^^^^^^^^^^
The Smith Vortex bottoms out on the muzzle face, no washers required.
Assuming the crown is cut square to the bore, i cant see it causing any issues. Assuming that the flash hider in question also has a face in the proper position that is also square.
I wasn't talking about a crown that's not square.
Now that I think about it, it's possible that compressing the muzzle is better than stretching it.
I wasn't talking about a crown that's not square.
Now that I think about it, it's possible that compressing the muzzle is better than stretching it.
At 20 ft/# you are NOT stretching or compressing anything. Tell me how you could compress without stretching anything. Typical claim based on internet BS. Draw yourself a picture depicting where the forces oppose each other in both scenarios.
I should have said tension and it ain't Internet BS either. If compression and tension didn't occur, the threads wouldn't hold.
The most precise way to torque a bolt is measure how much the bolt is stretched. For example, the installation of the main rotor blades on a Robinson R44 is very critical. So critical that torque isn't measured in ft/lbs, but by measuring bolt stretch. Engineers base in/lbs & ft/lbs torque specs on how much it stretches the bolt.
When a muzzle device is torqued against the shoulder of the barrel, the barrel is placed under tension. The majority of that tension will be concentrated between the threads and shoulder. Stretching does occur. Over torquing the muzzle device has been observed to have a negative effect on precision.
If the muzzle device is torqued against the crown, the barrel will experience compression forces mostly at the crown.
Hmm...
I should have said tension and it ain't Internet BS either. If compression and tension didn't occur, the threads wouldn't hold.
For example, the installation of the main rotor blades on a Robinson R44 is very critical. So critical that torque isn't measured in ft/lbs, but by measuring bolt stretch.
Well, yeah, but is the Robinson R44 a Tier 1 helicopter?
Sorry I jest.
I think this is going to be like the old does the recoil begin before or after the projectile leaves the bore discussion.
I am curious, though, about this: Now that I think about it, it's possible that compressing the muzzle is better than stretching it. Are you thinking that linear compression would enlarge the bore and that linear extension would tighten it? What about the mating surfaces of the crown and muzzle device? Just curious.
Stretching from over torquing a muzzle device seated against the shoulder will be concentrated between the threads and the shoulder. Stretching will thin and lengthen the material. The stretched portion will be like a bulge in the bore.
Over torquing a muzzle device that seats against the crown will compress the material at the crown. The compressed material will thicken and shorten. The bore will have a taper.
I'm thinking the barrel might resist distortions from compression better than from stretching. But that's pure speculation on my part.
Okay, I can understand that.
I recall reading a thread talking about this a long time ago, I've been searching for a while without finding it so here goes.
Specifically talking flash hiders that do not need to be indexed, like AAC blackouts, NOT suppressor-bearing hiders, is it considered acceptable to install one without crush or peel washers and simply torque it down on the face of the barrel, that is, the hider is sitting on the face of the muzzle instead of the shoulder of the barrel behind the threads? Meaning the muzzle device does not contact the shoulder of the barrel at all.
Knowing many barrel designs simply don't have a shoulder (or too small of a shoulder) to hold a washer/muzzle device due to their small diameter, I'd be inclined to think this would be fine.
However has anyone found detriments towards accuracy and/or strenght of using this method?
Typically the muzzle devices that go on in such a manner do not require much tension or torque to install them.
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