View Full Version : Flash hider torque specs that cause accuracy issues
Eurodriver
03-27-19, 21:50
Someone besides me has to have done it.
You go to install a suppressor mount and you think you’ve got the torque wrench set to 25 ft lbs and it ends up not being set at all so it never clicks. Next thing you know you’re at the range getting 30” groups at 50 yards.
The above happened to me with a 12.5” bcm. I removed the FH and the problem went away however that FH attached to any other rifle in the future always had accuracy issues that were so bad I worried about baffle strikes. I ended up throwing it away.
It got me wondering how much torque I put down and how much is needed to replicate that. I usually torque to 25, but have mistakenly torqued to 35 and that even seemed to cause accuracy issues though not to the same extent 90+ did.
Thoughts?
Five_Point_Five_Six
03-27-19, 22:24
I bought a used Colt upper some years ago that had the birdcage threaded all the way up to the shoulder without a crush washer. I wasn't getting 30" groups but they were bad. When I went to remove it, I thought I was gonna need a breaker bar. Once I got it off, added a crush washer, and retorqued to spec, accuracy was fine.
If I had to put a number on it, I'd say it was torqued to at least 75 ft lbs or more.
This is why I use shims now.
Edit: By "shims", I mean accu-washers.
1/2 x 28 threads? I know over torquing can affect accuracy, but not to the extreme that you describe. Something else was going on there - like a MD problem, as you indicated.
It's also possible that "over" torquing doesn't have a noticeable affect on accuracy at all. I did an experiment on a DD 14.5" with an A2 FH with torque values from 20-70 ft-lbs in 10ft-lb increments and had no difference in accuracy. I also had a 12.5" that showed approximately 100% increase; 2.5" 10 round groups @ 100yds with 25 ft-lbs, increased to 5" with torque value of 50 ft-lbs. So, I believe that recommended FH torque should be used, but high torque doesn't automatically mean problems. (shims used on all MDs)
It's not a problem with our *big* 5/8-24 threads...
https://dqzrr9k4bjpzk.cloudfront.net/images/812059/966837860.jpg
^^^
I'd like to see this, at least as an option, on more barrels and MDs.
vicious_cb
03-28-19, 00:31
I shim then hand tighten with rocksett the MDs on all my barrels now. Never had one come off.
It's not a problem with our *big* 5/8-24 threads...
https://dqzrr9k4bjpzk.cloudfront.net/images/812059/966837860.jpg
This.
When I built a 3 gun rifle, I put on a MD with crush washer and torqued to 25. The rifle would not shoot better than 1.5" groups with a match barrel. Very frustrating and disappointing. 2 years later I put an AFAB with shims on a new rifle and decided to try the shims on the 3 gun rifle. Groups shrank to .5".
I shim then hand tighten with rocksett the MDs on all my barrels now. Never had one come off.
I do the same. Works perfectly. You can get a bottle of rockset that will last you a lifetime for $15.
So what I'm hearing so far is that if you overtorque your muzzle device and get poor accuracy, you haven't necessarily done permanent damage and can often correct the issue?
That's good to know.
I badly overtorqued the first muzzle device I ever replaced on an AR because I had no idea what I was doing. It didn't seem to affect accuracy too negatively but later on when I realized my mistake and corrected, accuracy was pretty much the same, but I always kind of wondered if I had done any permanent damage with my initial botched installation.
I don’t use a torque wrench with muzzle devices. I use a fairly small crescent wrench. I start by cleaning the threads with alcohol wipes. I shim it close to clocked by hand, remove it, clean the threads again with alcohol, apply a dab of rocksett. Then I apply enough torque to time it. Done.
I removed the FH and the problem went away however that FH attached to any other rifle in the future always had accuracy issues that were so bad I worried about baffle strikes. I ended up throwing it away.
I think you threw away a bad muzzle device. 30" groups at 50yds is not something I would blame on excess torque.
Hammer_Man
03-28-19, 14:16
I don't like to exceed 20 - 23 ft. lbs. when torqueing a muzzle device. I will work the shims until I get the result I want, I don't care how long it takes.
So what I'm hearing so far is that if you overtorque your muzzle device and get poor accuracy, you haven't necessarily done permanent damage and can often correct the issue?
That's good to know.
I badly overtorqued the first muzzle device I ever replaced on an AR because I had no idea what I was doing. It didn't seem to affect accuracy too negatively but later on when I realized my mistake and corrected, accuracy was pretty much the same, but I always kind of wondered if I had done any permanent damage with my initial botched installation.
Doubtful you did long term damage, rather your initial job didn't effect the barrel's natural inherit accuracy.
It's my understanding that the over torqueing degrades the accuracy through negatively effecting the barrel's harmonics.
gunnerblue
03-28-19, 21:47
I shim then hand tighten with rocksett the MDs on all my barrels now. Never had one come off.
Same, though perhaps a smidge more than hand tight
I'm mechanically challenged so I like my Vortex, spin it on hand tight and dump a mag and it's good to go.
I noticed an improvement is group size too when going from the A2 that came on my 6920 to the Vortex.
Ned Christiansen
03-30-19, 13:03
I saw one where the bore was collapsed .004 by over torquing. Threads were stripped too, not that takes gorilla arms. "Gun did not shoot well". Taking off the flash hider did not fix anything, the constriction was permanent and in fact was on its way to wearing back out to full diameter via shooting.
i have also seen revolvers where the barrel was tq'd too tight causing a visual constriction in the bore.
I saw one where the bore was collapsed .004 by over torquing. Threads were stripped too, not that takes gorilla arms. "Gun did not shoot well". Taking off the flash hider did not fix anything, the constriction was permanent and in fact was on its way to wearing back out to full diameter via shooting.
i have also seen revolvers where the barrel was tq'd too tight causing a visual constriction in the bore.
How could people be so dumb? Torque on flash hiders, barrel nuts, etc. is common sense to any man worth a shit. I do own a torque wrench, but rarely use it.
I've never installed a muzzle device for a suppressor...I perceive that to be altogether different than a plain old muzzle device and I've installed many of those though the years. Many years ago I used shims, found them to be a PITA. Now I only use crush washers for (non-suppressor) muzzle devices. More than 90 degrees, less than 360. Never an issue. I can't imagine going back to shims.
granitestater
03-31-19, 20:41
When I built a 3 gun rifle, I put on a MD with crush washer and torqued to 25. The rifle would not shoot better than 1.5" groups with a match barrel. Very frustrating and disappointing. 2 years later I put an AFAB with shims on a new rifle and decided to try the shims on the 3 gun rifle. Groups shrank to .5".
A smith vortex will do the same thing without the hassle of getting the correct number of shims. Just screw it on and it self tightens and doesn’t cause accuracy issues.
http://www.smithenterprise.com/products06.05.html
A smith vortex will do the same thing without the hassle of getting the correct number of shims. Just screw it on and it self tightens and doesn’t cause accuracy issues.
http://www.smithenterprise.com/products06.05.html
While the Vortex is a great flash suppressor, you won’t see many on 3 Gun rifles, and it is also not similar to the AFAB.
granitestater
04-01-19, 06:03
While the Vortex is a great flash suppressor, you won’t see many on 3 Gun rifles, and it is also not similar to the AFAB.
I didn’t say it was similar. The vortex costs less and is not a compensator. But... I personally don’t see the need for a comp on a .223 rifle and I don’t have the patience to fool with shims or peel washers or whatever. The s itch is quick, easy doesn’t destroy accuracy and almost eliminates muzzle flash.
I didn’t say it was similar. The vortex costs less and is not a compensator. But... I personally don’t see the need for a comp on a .223 rifle and I don’t have the patience to fool with shims or peel washers or whatever. The s itch is quick, easy doesn’t destroy accuracy and almost eliminates muzzle flash.
You quoted a user that was talking about a comp/brake on a gamer gun (if you think brakes are useless, get a shot timer.), and specifically the AFAB.
You didn’t say it was similar. You literally said “a Smith Vortex will do the same thing”.
I like the Vortex also; just pointing out that it is a different tool for different tasks.
Eurodriver
04-01-19, 07:37
I only run A2s unless the rifle has a suppressor. Suppressor mounts typically need torque and if you’ve ever tried to remove a can that’s been shot 700-1000 times without removal you’d know why torque and rocksett are needed.
If you’re torquing a basic FH or comp more than a smidge you’re doing it wrong.
The flip side is if you’re over torquing a suppressor mount that’s wrong too. I’ve messed up both.
Eurodriver
04-01-19, 08:15
It's not a problem with our *big* 5/8-24 threads...
https://dqzrr9k4bjpzk.cloudfront.net/images/812059/966837860.jpg
You have 5/8-24 on 5.56 guns? Interesting. Why?
Edit: I mean I know it’s “better” but what made you go with that.
You have 5/8-24 on 5.56 guns? Interesting. Why?
Edit: I mean I know it’s “better” but what made you go with that.
I'm not Clint, but here is the thread dedicated to what he is doing with his barrels. https://www.m4carbine.net/showthread.php?209362-BRT-OPTIMUM-Barrels
We consider threads to be an integral part of the overall barrel profile.
1/2-28 threads were a good choice for the lightweight barrel profile of the original M16 and became standard.
Heavier profile barrels were designed but retained the small threads mostly because it was "standard" and worked well enough to secure existing muzzle devices.
Striving for improvement often involves revisiting past design decisions in light of the current landscape of requirements.
Two recent trends helped tip the balance in favor of us making the change to larger threads.
On the commercial side, the popularity of larger caliber AR variants in 6.8SPC and 300BLK has greatly increased the number and availability of 5/8-24 muzzle devices.
On the technical side, the popularity of suppressors has driven the need for a stronger attachment method.
While a 1/2-28 thread is completely sufficient to secure a 2oz flash hider with a crush washer, a 16oz suppressor hanging 8" past the muzzle with a shimmed QD mount is a different matter altogether.
You have 5/8-24 on 5.56 guns? Interesting. Why?
Edit: I mean I know it’s “better” but what made you go with that.
We consider threads to be an integral part of the overall barrel profile.
1/2-28 threads were a good match for the lightweight barrel profile of the original M16 and became standard.
Heavier profile barrels were designed but retained the small threads mostly because it was "standard" and worked well enough to secure existing 2 ounce muzzle devices.
Striving for improvement often involves revisiting past design decisions in light of the current landscape of requirements.
Two recent trends helped to the balance in favor of making the change.
The popularity of larger caliber AR variants in 6.8SPC and 300 BLK has greatly increased the number and availability of 5/8-24 muzzle devices.
Just as an FYI, some suppressor manufacturers do not make a 5/8x24 muzzle device for their 556 cans. IMO I think you would be way better off doing a taper with 1/2x28 vs eliminating a whole group from buying your barrels because they don't have the proper thread pitch.
Just as an FYI, some suppressor manufacturers do not make a 5/8x24 muzzle device for their 556 cans. IMO I think you would be way better off doing a taper with 1/2x28 vs eliminating a whole group from buying your barrels because they don't have the proper thread pitch.
He also makes barrels with the traditional threading. IMHO, his offerings are worth the squeeze if they fit your equipment set up.
Just as an FYI, some suppressor manufacturers do not make a 5/8x24 muzzle device for their 556 cans.
I doubt I'd ever buy a 5.56 can again anyway. Larger bore cans work every bit as well on 5.56 and can be run on the larger caliber guns too.
I doubt I'd ever buy a 5.56 can again anyway. Larger bore cans work every bit as well on 5.56 and can be run on the larger caliber guns too.
Same here. I'm over 9 months into a wait for my first suppressor, and wishing I'd bought a 308 can. Now I'll have to buy a 308 can before I get to a 22lr can.
Same here. I'm over 9 months into a wait for my first suppressor, and wishing I'd bought a 308 can. Now I'll have to buy a 308 can before I get to a 22lr can.
I think today is the last day for the Sandman-k at $569... Just sayin'
Sig and Surefire don't have solutions for 5.56 on 5/8-24, but pretty much everyone else does.
https://dqzrr9k4bjpzk.cloudfront.net/images/812059/951372385.jpg
Both our 16" LPR and 14.0/14.5" MPC barrels have 1/2-28 threads, so there are OPTIMUM barrel options for users that need to stay with traditional threads for whatever reason.
Just as an FYI, some suppressor manufacturers do not make a 5/8x24 muzzle device for their 556 cans. IMO I think you would be way better off doing a taper with 1/2x28 vs eliminating a whole group from buying your barrels because they don't have the proper thread pitch.
Sparky5019
04-07-19, 11:47
Interesting result. I’ve over torqued a couple with questionable affect on accuracy but nothing as severe as 30”. I typically install them to the spec recommended the MD manufacturer with the shim provided or SF shim kits then Rocksett.
One interesting twist I’ve found over the years when switching MDs around or reconfiguring an upper...
I’ll check thing with a suppressor alignment rod to ensure concentricity and sure enough it’ll be off. I presume it’s from Rocksett residue from the previous install. Now I’ve come to chasing the threads in the brake and on the barrel to ensure all residue is gone and the threads are “virgin”. Works every time.
I agree. I think your MD was bad in some respect though you could have “choked” your rifle some. Lol.
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