View Full Version : FH Torque
Need some opinions here. I was torquing up a SiCo Omega FH on my 14.5" BFH LW barrel today and thought my results were a little strange. I set the torque wrench to 30 ft/lbs and went after it, but after at least a full revolution, I still hadn't hit the 30 ft/lbs...and I was cranking on it pretty hard to what felt like way over the 30 ft/lbs. I just recently used the wrench putting the barrel on and didn't have any trouble hitting the torque values I needed, so I don't think it's the wrench. Also, wasn't using any washers or shims.
Any ideas why that happened?
I would tend to hesitate torquing the FH to 30 ft/lbs. Not all muzzle attachments fit all 1/2"x28 barrels. Looking at different prints, there are some that are clearly not compatible. Not saying that is the case here, but something to always be aware of.
I'm pretty sure 30 ft/lbs is within the acceptable torque range for a muzzle device. And being that this is a part from a quality manufacturer, I would be surprised if it was a fit issue. It screwed on with no strange issues. The problem came when I torqued it.
I would still be hesitant about the torque load, was the wrench a recently calibrated dial type?
I would not go beyond the 15-20 foot pounds called out for in the tech manual, 30 foot pounds is a bit much.
What kind of torque wrench did you use?
BufordTJustice
11-27-15, 20:55
You said you didn't use any washers. This might be a problem if your barrel shoulder didn't capture the rear of the muzzle device. I'd advise using some type of shim just so you don't damage the barrel threads or the muzzle device threads.
And 30 ft-lbs is fine. Might even want to use some rocksett as well.
You said you didn't use any washers. This might be a problem if your barrel shoulder didn't capture the rear of the muzzle device. I'd advise using some type of shim just so you don't damage the barrel threads or the muzzle device threads.
And 30 ft-lbs is fine. Might even want to use some rocksett as well.
What you described with the barrel shoulder and rear of FH occurred to me after I got back from the range. I'm going to take it apart tomorrow and inspect it. I really hope my tendency to monkey grip things didn't screw anything up. What washers would you suggest if a suppressor is in its future? (That was the reason I didn't use any in the first place)
And to answer the questions regarding my torque wrench, it's a budget brand and hasn't been calibrated. However it's only been used maybe 10 times, and without a hitch, so I didn't think that was the problem. What Buford suggested is my leading theory right now.
BufordTJustice
11-28-15, 00:56
What you described with the barrel shoulder and rear of FH occurred to me after I got back from the range. I'm going to take it apart tomorrow and inspect it. I really hope my tendency to monkey grip things didn't screw anything up. What washers would you suggest if a suppressor is in its future? (That was the reason I didn't use any in the first place)
I am partial to the Precision Armament shim set. I use them exclusively. Just good quality kit.
I use a Harbor Freight torque wrench for all my work...it tests near as can't be distinguished from two Snap-On and one Craftsman wrench (all three of which are calibrated regularly) every time I get the chance. I paid $11 for my 3/8" and 1/4" drive and $15 for my 1/2" drive. Got the entire damn set for under $40 AND I got a free tape measure and set of carpenter's clips to boot.
Am I saying that HF stuff is = to Snap-On? Hell no. Will I be replacing my HF wrenches any time soon? Also hell no (or, at least until they can't hold calibration any more).
I suspect you were basically threading the barrel shoulder past the existing threads. Shouldn't be a huge deal as long as the threads on the muzzle device are still good. Keep us updated.
If you don't have a set of prints to reference, a good "rule of thumb" is to simply twist the parts together with finger pressure. They should twist together with moderate effort and hit a quick "wall" of seating tension. Some combinations require a shim, preferably a surface ground one, others do not.
Not all muzzle devices play well with all barrels. It isn't uncommon to run into issues with parts that are not made to fit the same print.
RVTMaverick
12-02-15, 12:31
Hey Ironman,
Did you get it figured out?
Quick question & Heads UP on your "torque wrench" IS Yours the style which has the square driver that pops back and forth through the wrench head? Or does yours have the lever that on the back of the head that switches back and forth for right hand and left hand threads??
IF yours doesn't have the lever or knob style, then it is quite possible you have the driver in Wrong side = said torque wrench is then NOT going to torque anything, it will just act like a regular wrench,... unless you just happen to be working a left hand thread. LOL ;)
Peace Jeff
PS. Even IF BufordTJustice is correct about the threads/shoulder (FWIW: this advice does Sounds good to me too).... 30 foot pounds should kick over easy enough.... 2 cents
Wayne Dobbs
12-02-15, 16:10
The factory torque setting for the A2 FH is 25 - 30 ft-lbs, with the variance there so you can align the center vent of the compensator.
20-30# is the standard. I prefer 20 on dry-torque, and after Rocksett, I will push it until it lines up (usually a HAIR over 20#, if the Rocksett got a little tacky while I was final-aligning shims,etc.). I simply set the wrench to 25 for the final torque, and torque until alignment. I don't care if it "snaps", because I already know its GOING TO BE at least 20#. I just don't want to go over 25.
When you over-torque a muzzle device, it causes the muzzle to "bell" out. This can of course cause accuracy issues, and in general, is just bad to bend the barrel at any point, even the end.
There's good reason to not induce a torque load that could distort the bore and cause other problems.
I would tend not to torque much over 20 ft/lbs for that and other reasons. Unfortunately, without knowing much about a selected barrel or muzzle device if that limit could be 24, 29, or 19 ft/lbs.
If a universal print in manufacturing standard is openly released and accepted by all, or hopefully most. Some base issues can be resolved besides a torque value in range that clearly does not work for all. Some say that it is, but is it really in use?
There's good reason to not induce a torque load that could distort the bore and cause other problems.
I would tend not to torque much over 20 ft/lbs for that and other reasons. Unfortunately, without knowing much about a selected barrel or muzzle device if that limit could be 24, 29, or 19 ft/lbs.
If a universal print in manufacturing standard is openly released and accepted by all, or hopefully most. Some base issues can be resolved besides a torque value in range that clearly does not work for all. Some say that it is, but is it really in use?
Surefire and AAC have both conducted quite a bit of testing. There is a trade-off between bore distortion, and keeping your suppressor on the rifle. If I were not shooting suppressed, I'd torque to 15#. If I were mounting a suppressor, or using an aggressive brake, 20-30. AAC and SF both publish 20-30#.
Yeah, I can pretty much agree.
The higher torque really isn't needed for most, even with a can. Without knowing when issues arise with the higher torque, what gamble are you willing to place?
Many, with lower magnification probably wouldn't notice, but that doesn't mean the issue doesn't exist.
I would tend to prefer a precision ground shim with Rocksett in the 20 lbs range over the 30 range
The issue begins at around 25#, technically, and noticeably past around 35 to 40ish.
steyrman13
12-02-15, 18:20
I recently removed a "pinned and welded" 14.5" barrel and found it to not be welded or pinned. The hole on the muzzle device was threaded and it had a small set screw that reached into the barrel (where it was drilled for a pin) and then soldered the hole above the set screw to make it permanent. If you have a SBR lower or 16" barrel you could use this design without the solder and use rockset with the correct shim and go with a much lower torque value on the MD correct? Then you have a pin that will definitely keep the MD from backing off and a low torque value to keep from hurting accuracy.
Am I missing something?
Ps I have not done this, just thinking and putting it out there to see what would be wrong with it. The rifle I found it on has had 4K plus rounds through it suppressed and never moved or had problems.
I use proper torque due to harmonics issues. Real or perceived. My .02
That depends on the parts that could be compared. Sure many can do that, that decision may not be as inclusive as many think.
Jwknutson17
12-02-15, 18:39
When torquing a MD, I just grab a 19mm wrench, standard "open end / box", and time it with that. It would be pretty hard to get into any high torque with it.. unless of course your hanging off the end of it. Putting a muzzle device on is not a science. Rocksett and some shims and be done with it.
If you can not freely spin the MD all the way to the collar, you need to see why, and stop tightening right away..
It's a good heads up to say that the parts should thread on with moderate finger pressure until it stops abruptly with a shoulder. That does not mean that the system is good to torque to X amount of torque to that. That may, or may not induce issues depending.
Sorry for the absense here guys. In the middle of moving to a new place and this had to go on the back burner. I finally got a chance to pull off the FH and inspect everything. And I also found my problem. Somehow, between the last upper I put together a month ago and now, my torque wrench decided to stop working. It gives me a torque value (clicks when reached) for left hand threads, but for standard threads, it is basically acting like a breaker bar. I should have known beter to stop monkey gripping it, but it looks like everything is still in good shape.
Threads in the FH look good, but the only sign of wear is on the shoulder of the barrel threads. Not sure if there was a "false shoulder" that I pushed back into the rest of the shoulder, but it should still hold the FH nicely once I can get an accurate torque. Any suggestions/comments?
Here's what it looks like:
http://i1125.photobucket.com/albums/l583/bgonzo8/IMG_1642_zpscrzxp4ap.jpg
Hey Ironman,
Did you get it figured out?
Quick question & Heads UP on your "torque wrench" IS Yours the style which has the square driver that pops back and forth through the wrench head? Or does yours have the lever that on the back of the head that switches back and forth for right hand and left hand threads??
IF yours doesn't have the lever or knob style, then it is quite possible you have the driver in Wrong side = said torque wrench is then NOT going to torque anything, it will just act like a regular wrench,... unless you just happen to be working a left hand thread. LOL ;)
Peace Jeff
PS. Even IF BufordTJustice is correct about the threads/shoulder (FWIW: this advice does Sounds good to me too).... 30 foot pounds should kick over easy enough.... 2 cents
Jeff,
My wrench has the lever on the back, so I would have known if it was set for left hand threads. Thanks for the help.
I, personally, never go over 30 Ft/lbs
YMMV
vicious_cb
12-20-15, 00:33
I, personally, never go over 30 Ft/lbs
YMMV
Since I dont suppress my ARs I dont follow any set torque value. After listening to the advice of some top high power guys I am now of the opinion that any torque over the minimum required to keep the muzzle device on the barrel negatively affects accuracy. Now I simply apply rocksett, hand tighten and seat it with a jerk of a wrench and let it dry.
That "jerk of a wrench" might be more tq than you think...
Since I dont suppress my ARs I dont follow any set torque value. After listening to the advice of some top high power guys I am now of the opinion that any torque over the minimum required to keep the muzzle device on the barrel negatively affects accuracy. Now I simply apply rocksett, hand tighten and seat it with a jerk of a wrench and let it dry.
I actually don't go above 30 for that reason... because at around that point, the bore can actually constrict up to half a thou, and yup, negatively affect precision.
vicious_cb
12-20-15, 03:25
That "jerk of a wrench" might be more tq than you think...
Not really, Ive tested it without rocksett and I can easily remove the muzzle device with my bare hands pretty easily. I dont apply much force at all when I seat the MD.
Roger that. As to rocksett, I can't even tell when it's been used. It's more of a resonance damper than anything. Shear value is negligible. All these people whining about how permanent it is likely have no idea how much torque was used on their muzzle device...
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