View Full Version : Muzzle Devices and Torque
BrigandTwoFour
02-09-11, 15:20
Ran a few searches on this, didn't quite come up with the answer I was satisfied with.
So here's the situation. I had a local guy (former military who stayed here in central MT and opened a shop) assemble my upper. From what I can tell, he did good job of it. However, what has been concerning me is the torque level on the muzzle device.
In this case, I have an AAC blackout (non suppressor mountable). If any of you have used this before, it does not come with a washer, since AAC claims it does not need to be timed.
It appears that the guy who assembled it wanted the flats to line up on the side for aesthetics sake. If, by doing this, he overtorqued the device, how much of an effect on accuracy might this have? The barrel is a Centurion 16" CHF LW.
The rifle functions flawlessly so far, but the accuracy I'm seeing is not quite what I would expect. At 50 yards from a rest, I seem to be peppering rather than grouping. For comparison, my M1A with irons puts a nice big ragged hole under the same conditions.
My first thought might have been the irons (Magpul MBUS), and I have not gotten to test again with the new TR24 (mounted yesterday). The problem may have been the sights, or ammo (mostly Hornady 55gr training). But if those effects are minimized, what is the chance of the muzzle device causing that much inaccuracy?
How much have ya'll seen the effects of muzzle device torque effect a weapons performance?
There is so much going on here. Let me see if I can answer.
Ran a few searches on this, didn't quite come up with the answer I was satisfied with.
So here's the situation. I had a local guy (former military who stayed here in central MT and opened a shop) assemble my upper. From what I can tell, he did good job of it. However, what has been concerning me is the torque level on the muzzle device.
In this case, I have an AAC blackout (non suppressor mountable). If any of you have used this before, it does not come with a washer, since AAC claims it does not need to be timed.
It appears that the guy who assembled it wanted the flats to line up on the side for aesthetics sake. If, by doing this, he overtorqued the device, how much of an effect on accuracy might this have? The barrel is a Centurion 16" CHF LW. How do you know it is overtorqued? What does AAC say it should be set at? If you have doubts then remove it and have it redone. They are pretty simple to do and don't require master armorer skills.
The rifle functions flawlessly so far, but the accuracy I'm seeing is not quite what I would expect. At 50 yards from a rest, I seem to be peppering rather than grouping. For comparison, my M1A with irons puts a nice big ragged hole under the same conditions.
My first thought might have been the irons (Magpul MBUS), and I have not gotten to test again with the new TR24 (mounted yesterday). The problem may have been the sights, or ammo (mostly Hornady 55gr training). But if those effects are minimized, what is the chance of the muzzle device causing that much inaccuracy? You need to use match ammo and an optic and a steady shooting position of you want a better indication of it's accuracy. I would also shoot at 100 yards not 50.
How much have ya'll seen the effects of muzzle device torque effect a weapons performance? I think it is entirely possible if he overtorqued it that something could happen. I think that subject has been discussed here before.
BrigandTwoFour
02-09-11, 16:26
It certainly has been discussed, but only that it has an effect. I've never seen any discussion about how much of an effect it has, though. I know that the recommended amount is hand tight or a bit past it. But I guess I'm asking if the difference is a couple inches at 300 yards, or all over the place at fairly close range.
The optic will get zeroed at 200 when I get the chance. Though there is a lack of any kind of match ammo around where I live, and I don't do hand loading (yet).
I never moved out past 100 or so with the mbus because I never quite got it right at 50. It is frustrating because I know I am capable of using irons out to 200 with my m1a, but those sights are a whole different ballgame compared to mbus.
If it were me, I would remove the flash hider and reinstall it if you have doubts.
Match ammo can be easily ordered from the internet. Try some Prvi Partizan 75gr. Match ammo.
It certainly has been discussed, but only that it has an effect. I've never seen any discussion about how much of an effect it has, though. I know that the recommended amount is hand tight or a bit past it. But I guess I'm asking if the difference is a couple inches at 300 yards, or all over the place at fairly close range.
The optic will get zeroed at 200 when I get the chance. Though there is a lack of any kind of match ammo around where I live, and I don't do hand loading (yet).
I never moved out past 100 or so with the mbus because I never quite got it right at 50. It is frustrating because I know I am capable of using irons out to 200 with my m1a, but those sights are a whole different ballgame compared to mbus.
BrigandTwoFour
02-10-11, 00:02
I don't have the tools (vice, vice block, etc) to remove it myself. But I don't think it will be an issue.
I've been avoiding mail ordering ammo for a while, but for no good reason. After that last post, I bought several boxes of 75gr TAP FPD and BH 77gr SMK for some experimentation.
Over torquing the muzzle device can result in distortion of the threads and the bore in that area and have a negative impact on accuracy
Sound like "your guy" is an typical ill-informed usmil trained lego assembling parts monkey.
Where the flats are is of no import, but over-torquing a muzzle device can have ill effects. Yeah.. I shot service match before...
I would also be concerned with the torquing of the barrel into the upper. Screwing this pooch = crap downrange results. Threads ok? Index pin & slot good? lithium grease threads and tighten/loosen/tighten x3 min. Line up gas tube within a reasonable torque spec.
BrigandTwoFour
02-10-11, 09:59
I stood next to him during most of the assembly, and most and all of those steps were accomplished as far as the barrel mounting. However, I don't know if he used the proper amount of torque on the barrel nut either.
Frankly, the ideal solution would be to send the upper off to adco and have them redo it. But I'm just so wary about sending the upper off for the work. I'd rather wait until I at least get some testing done with the TR24 to see just how far off it might actually be.
But, this brings me back to the original question. Nobody seems to have an answer about how much of an effect the muzzle device torque has, only that it will adversely affect the accuracy. I'm just wondering if "adversely" means missing by a few inches at two hundred yards, or does it mean failing to get groups at all. I'm not really good enough to notice the former, but the latter is definitely a limiting factor.
I've had good luck with AAC muzzle devices happening to line up at aesthetically pleasing locations on my barrels, so that may have happened in your case. I highly doubt your gunsmith overtorqued your muzzle device enough to cause bad accuracy, as I use suppressor mount versions of the Blackout, and I torque my muzzle devices down VERY tight... I've had issues where carbon buildup on suppressor threads made the mount come loose when I was trying to remove the can! I've not noticed any issues with accuracy.
As for accuracy concerns, i'd want to use good ammo, specifically 77 gr SMK. I've bought factory loaded Privi 75 gr, and loaded 3000 of the projectiles for my own use... having shot Privi through my Compass Lake 1/8 SPR barrel, Noveske N4 14.5", BCM 16" mid length, LMT 14.5"... i've come to my personal conclusion that Privi 75 gr "match" ammo sucks balls compared to 77 gr Sierra Match King.
I'd get my hands on match ammo to judge accuracy. 55 gr Hornady training is not something i'd use to measure accuracy with.
...Nobody seems to have an answer about how much of an effect the muzzle device torque has, only that it will adversely affect the accuracy...
That's because it depends on how much the torque distorted the barrel. Some folks have had no trouble at all with their muzzle devices. Some report they must use the minimal torque in order to gain best accuracy. Some have found even slight overtorquing causes shots to be scattered all over the place. Best thing to do is remove the muzzle device and test your groups without it, then with it installed using minimal torque
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