Barrel torque vs precision?

[Dusty Stevens]

Fasteners that size typically don't have 1/2" holes through the middle of them. That kind of torque would likely yield (permanently deform) the barrel tenon at the chicken groove or first thread.

IMO, the torque only has to prevent the shoulder junction (and recoil lug if used) from loosening under the forces of firing due to tenon stretch (in the chicken groove) as it elastically elongates. One can calculate the required torque to place that much clamping force on the joint, so that things don't move about and depend on the threads and shoulder for positional repeatability. In other words, it has to be tight enough to prevent the barrel from doing the funky chicken every time you fire.

I've calculated a required torque of 125 ft/lbs for my big cartridges (WSM) at max pressures. For little cartridges (smaller diameter, shorter length, or lower pressures), the required torque is less, a lot less. 223 Rem at 55Kpsi takes little more than 60 ft/lbs. These are lubricated joint numbers...

The easy solution for me is to torque them all to the same torque - enough for my biggest cartridges. When speaking to Ian Kelbly years ago, he told me they torque all barrels on steel actions to 150 ft/lbs, IIRC. That's where I got started looking into it.

And yes, I think it made a difference in my rifles going up from 80 to 125. It was a subtle effect. I don't know what going looser than 80 would look like. I've never done that.

As always, YMMV...

We didnt change the torque numbers if a turbine fastener had a bolt heater hole in it

 

[M-61]

I know the Panda recommended torque is 100 ft lbs and lubricated

With what? Huge difference.

 

[WSnyder]

I know the Panda recommended torque is 100 ft lbs and lubricated. I've talked to them and it's also in their written instructions. It sounds lot a lot and it is compared to most nuts and bolts in common use like a 3/8 or 1/4 inch. But, a barrel is much larger and going by a torque chart, the 100 is not out of line. I figure that the folks making the Kelby Panda know more than I do about their product, so I trust their suggestion.

With what? Huge difference.

P. Barrel Changing/Installation Instructions Before installing a new barrel, apply EP-2 (NCGI Grade 2) or equivalent bearing grease on the barrel threads and shoulder tenon or receiver face. Do not use metallic based “anti- seize” compounds. Using a Kelbly’s Inc., barrel vise and action wrench, first insert the barrel into the barrel vise and tighten the nuts on the barrel vise. Then, using the action wrench, turn the action with a minimum of 100 ft./lbs. of torque. If you do not own a torque wrench, use a T-handle rear entry action wrench and install the barrel with the same amount of torque as one would use on a typical lug nut for an automobile wheel.

 

[Rat Rifle]

P. Barrel Changing/Installation Instructions Before installing a new barrel, apply EP-2 (NCGI Grade 2) or equivalent bearing grease on the barrel threads and shoulder tenon or receiver face. Do not use metallic based “anti- seize” compounds. Using a Kelbly’s Inc., barrel vise and action wrench, first insert the barrel into the barrel vise and tighten the nuts on the barrel vise. Then, using the action wrench, turn the action with a minimum of 100 ft./lbs. of torque. If you do not own a torque wrench, use a T-handle rear entry action wrench and install the barrel with the same amount of torque as one would use on a typical lug nut for an automobile wheel.

I don’t torque My wheel lug nuts to 100 foot pounds.

 

[Lone Hunter]

P. Barrel Changing/Installation Instructions Before installing a new barrel, apply EP-2 (NCGI Grade 2) or equivalent bearing grease on the barrel threads and shoulder tenon or receiver face. Do not use metallic based “anti- seize” compounds. Using a Kelbly’s Inc., barrel vise and action wrench, first insert the barrel into the barrel vise and tighten the nuts on the barrel vise. Then, using the action wrench, turn the action with a minimum of 100 ft./lbs. of torque. If you do not own a torque wrench, use a T-handle rear entry action wrench and install the barrel with the same amount of torque as one would use on a typical lug nut for an automobile wheel.

What would be the recommended torque for nutted barrels like a Remage? I wouldn’t think the nut could stand 100 ft lbs.

 

[Rat Rifle]

What would be the recommended torque for nutted barrels like a Remage? I wouldn’t think the nut could stand 100 ft lbs.

I did 100’#’s once, I won’t do it again.

 

[dcali]

There's an interesting chapter in Rifle Accuracy Facts where Harold Vaughn argues that you can't really torque the barrels hard enough to keep them from gapping under firing loads, and then he goes on to solve the problem with a ramp thread profile to distribute the load to more threads. That allows for the very high torques he calculates that you need.

The thing is, there are lots of high end rifles shooting really small groups that aren't using anywhere near the torque that he calculated is "required". The way I reconcile this is that even if there is a slight momentary gap, who cares? if the action is square and the barrel is square, a .001" lateral move is going to open up your group .001". I can't imagine you'd get that much sideways movement, or we'd be measuring it. You have to wonder if the threads themselves help to keep it centered.

The other thing to note is that the calculations engineers use to figure out thread stretch from torque are *really* fuzzy. The geometry of a rifle barel/action makes it even fuzzier. Torque wrenches are at best a vague guess. The proper way to do it is to measure the bolt's stretched length after torquing it. You can't do that with barrel threads, so the next best option is to measure the angle of rotation past a witness line, and make sure the threads and shoulder are lubed consistently. Torque is the worst option - it's just too indirect. I'm convinced that 99% of the time, using torque wrenches for just about anything in shooting is just giving a false sense of confidence. Fancy wrenches are a waste of money.

 

[Dusty Stevens]

There's an interesting chapter in Rifle Accuracy Facts where Harold Vaughn argues that you can't really torque the barrels hard enough to keep them from gapping under firing loads, and then he goes on to solve the problem with a ramp thread profile to distribute the load to more threads. That allows for the very high torques he calculates that you need.

The thing is, there are lots of high end rifles shooting really small groups that aren't using anywhere near the torque that he calculated is "required". The way I reconcile this is that even if there is a slight momentary gap, who cares? if the action is square and the barrel is square, a .001" lateral move is going to open up your group .001". I can't imagine you'd get that much sideways movement, or we'd be measuring it. You have to wonder if the threads themselves help to keep it centered.

The other thing to note is that the calculations engineers use to figure out thread stretch from torque are *really* fuzzy. The geometry of a rifle barel/action makes it even fuzzier. Torque wrenches are at best a vague guess. The proper way to do it is to measure the bolt's stretched length after torquing it. You can't do that with barrel threads, so the next best option is to measure the angle of rotation past a witness line, and make sure the threads and shoulder are lubed consistently. Torque is the worst option - it's just too indirect. I'm convinced that 99% of the time, using torque wrenches for just about anything in shooting is just giving a false sense of confidence. Fancy wrenches are a waste of money.

You sure .001 movement in the action will only open a group .001? Even at 25yds?

 

[dcali]

You sure .001 movement in the action will only open a group .001? Even at 25yds?

If it's *sideways* movement, yes. (I'm simplifying here, but the point Im making is that angular movement is bad. Lateral movement, not so much).

 

[jackieschmidt]

I did 100’#’s once, I won’t do it again.

It would seem that with those slots cut in most Savage nut, they would distort pretty easily under anything past about 50 pound ft. They look pretty thin.
Does anyone know what grade of steel these nuts are machined from.?

When I did the barrel nut exercise a few weeks ago, I left the nut a multi flat. It is darn near as thick as the action, also made from 4142 at 38 RC. UGLY, but functional. I did not want any distortion in the nut.

 

[jackieschmidt]

There's an interesting chapter in Rifle Accuracy Facts where Harold Vaughn argues that you can't really torque the barrels hard enough to keep them from gapping under firing loads, and then he goes on to solve the problem with a ramp thread profile to distribute the load to more threads. That allows for the very high torques he calculates that you need.

The thing is, there are lots of high end rifles shooting really small groups that aren't using anywhere near the torque that he calculated is "required". The way I reconcile this is that even if there is a slight momentary gap, who cares? if the action is square and the barrel is square, a .001" lateral move is going to open up your group .001". I can't imagine you'd get that much sideways movement, or we'd be measuring it. You have to wonder if the threads themselves help to keep it centered.

The other thing to note is that the calculations engineers use to figure out thread stretch from torque are *really* fuzzy. The geometry of a rifle barel/action makes it even fuzzier. Torque wrenches are at best a vague guess. The proper way to do it is to measure the bolt's stretched length after torquing it. You can't do that with barrel threads, so the next best option is to measure the angle of rotation past a witness line, and make sure the threads and shoulder are lubed consistently. Torque is the worst option - it's just too indirect. I'm convinced that 99% of the time, using torque wrenches for just about anything in shooting is just giving a false sense of confidence. Fancy wrenches are a waste of money.

Vaughn is wrong. All of that special thread crap is just that, a bunch of crap.

I arrived at 80 pound feet years ago by snagging the barrel firmly, then placing a line connecting the barrel and action face. I tightened the barrel to where there was 3/32 space between the lines. On a 1.062 16 tpi, that is 80 pound feet.

I have also discovered that if you go past 120, the chamber will start to close enough to notice.

 

[Coyotefurharvester]

One of my AR upper assembly(20p cartridge) required 75 pound feet on the barrel nut. I kept having issues with poi shift during load development. Checked my torque wench, was actually yielding 36-37 flbs. Recalibrated the wench, applied 75 and haven't had an issue since.

 

[D Coots]

Vaughn is wrong. All of that special thread crap is just that, a bunch of crap.

I arrived at 80 pound feet years ago by snagging the barrel firmly, then placing a line connecting the barrel and action face. I tightened the barrel to where there was 3/32 space between the lines. On a 1.062 16 tpi, that is 80 pound feet.

I have also discovered that if you go past 120, the chamber will start to close enough to notice.

Liking your first sentence Jackie.

I read his book....if I recall correctly a lot of his info was done with a .270

Did he ever compete in Benchrest shooting???? What records did he set?

Another question....how does the crosshairs in your scope like it when the 100fp of torque is released?

 

[dave@aDave]

I don’t torque My wheel lug nuts to 100 foot pounds.

The best advice is to check your owner's manual.
All of the cars that I've owned had five wheel studs and specified between 90 to 100 lbf.
I have a F-350 dually that requires 150-165 lbf.
All of the semi trucks that I have driven are tightened to 600 lbf.
An interesting note:
When I started working a Texaco station many years ago I asked how tight should I tighten the lug nuts.
And older man said "Tighten them until they first squeak".
Some time later when I discovered torque wrenches, the first squeak happened around 90 lbf.
Important - - - the threads on the studs and nuts should be clean and NOT lubricated.
If your lug nuts have a flange instead of a bevel, makers say a small drop of oil on the flange.

 

[Rat Rifle]

^^ I’ve never lost a wheel or a barrel ^^

 

[Old Navy]

Wheel torque is based on several things. Wheel material, stud size, number of lugs etc. My Buick Lacrosse with alloy wheels is 110#.

 

[Rat Rifle]

Another opportunity for testing to see if it proves or disproves improvement on target.

 

[Carl S]

If the barrel shoulder is square and the action face is square-square to each other you don't what much torque to make them lock together by hand.how many times has one had to use the action wrench to remove the action when checking for headspace-final fit.all these high torque values arnt necessary.i use 70 lbs/ft.i dont want any stress in the action-chamber area.never had one come loose yet or that torque value cause any issues.

 

[Rsadams]

Barrel torque just like action torque make a difference..... I am not sure on a bolt action but I know barrel torque on an AR platform can make a big difference in how the barrel shoots especially if over done....

 

[dcali]

Vaughn is wrong. All of that special thread crap is just that, a bunch of crap.

I arrived at 80 pound feet years ago by snagging the barrel firmly, then placing a line connecting the barrel and action face. I tightened the barrel to where there was 3/32 space between the lines. On a 1.062 16 tpi, that is 80 pound feet.

I have also discovered that if you go past 120, the chamber will start to close enough to notice.

That was the conclusion I came to. I don't know exactly which part he's wrong about, but he missed something, or people wouldn't be shooting so well with such light torques.