Gunsmithing Barrel Torque?

[Wheres-Waldo]

I remember asking a while back about what was recomended for the torque value of a barrel into the action?

My barrels' headspace was checked at the smith with the 100ft-lb standard, but if I can maintain the same headspace at 50-60 ftlbs, would I be doing myself or my rifle any harm by just running my barrels at that value?

 

[BOLTRIPPER]

Re: Barrel Torque?

all the gunplumbers i know just hold their tongue in cheek and tap the wrench and call it good........i'm talking steel actions here.

 

[Graham]

Re: Barrel Torque?

I've seen barrels unscrew during matches.

 

[BOLTRIPPER]

Re: Barrel Torque?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body">I've seen barrels unscrew during matches.</div></div>


blue lock-tite could be your friend

 

[Graham]

Re: Barrel Torque?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: BOLTRIPPER</div><div class="ubbcode-body">blue lock-tite could be your friend</div></div>I need more blue friends. My only purple friend is Barney.

 

[PCR]

Re: Barrel Torque?

I thought this was a good read.

Barrel Torque

 

[Graham]

Re: Barrel Torque?

Torque should be enough to give consistent accuracy under all temperatures and for the barrel not to come loose during use.

 

[Keith Johns]

Re: Barrel Torque?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Graham</div><div class="ubbcode-body">I've seen barrels unscrew during matches. </div></div>

What do you think was to blame? just vibrations?

Which barrel manufacturers out there use Left hand twist rifling? That would be the main thing Id think of to loosen a barrel.

But most I know of are right hand.

 

[CSiebert]

Re: Barrel Torque?

I have 4 different barrels for my Kelbly and I twist them on and off all the time without torque wrench. My smith just told me to snug them up good, I have checked my brass dimensions and they don't change after barrel is reinstalled.

 

[cal50]

Re: Barrel Torque?

Anytime I installed a barrel I threaded the barrel to fit the action with minimal or zero play (precision fit). Minimal torque and red loctite completed the job once headspaced.

I have never seen a barrel back out unless the threads were fitted poorly to begin with. If this is the case loctite and torque is not substitute for proper fitting.

 

[Keith Johns]

Re: Barrel Torque?

Red loctite?

Damn







Im not that worried about a right hand twisted barrel tightened on with a 14" 4lb wrench coming loose. Im not sure what poundage we tighten ours to but I cant imagine one coming loose.
It makes sense that a certain poundage might be required for 100% flank contact but it would depend on the thread quality/fit(as someone else already said) 0f both the barrel tenon and the receiver.


I would guess we tighten to about 50 or 60 foot pounds. And we degrease very well before screwing them together.

 

[Wheres-Waldo]

Re: Barrel Torque?

PCR, that is a good read.

I would be VERY suprised if 60 ft-lbs. manages to come loose from anything shy of intentionaly taking the barrel off.

I also would like to stay away from any kind of loc-tite, as the last thing I want it to have to disassemble the whole rig to pull out a barrel under heat.

I know my headspace reamains constant, and my barrel is physicly tight enough that I wouldnt at all worry about losening. Im gonna keep things at 60lbs I think.

 

[JFComfort]

Re: Barrel Torque?

What kind of thread/shoulder crush are you seeing?

I've heard anywhere from 0.0005" to 0.0015" Was thinking of going 0.001" deep on the head space to account give myself some wiggle room.

 

[Keith Johns]

Re: Barrel Torque?

I get .001" on average of crush.

So I aim for "Go"+.003

After crush, I end up at Go+.002 (perfect)

 

[Clark]

Re: Barrel Torque?

Here is a video of me needing 540 foot pounds of torque + Kroil to get 1937 Mosin Nagant receiver off the barrel.

I cleaned it up, lubed it, and put it back on to the same original location marks on barrel and receiver, and it took 200 foot pounds to get it there.

http://www.youtube.com/watch?v=YOjYro4w0Bc

 

[MikeeBooshay]

Re: Barrel Torque?

Clark, I loosen lots of big nuts and bolts (gas turbines ). One very simple rule is twice the torque to loosen as tighten, unless heat, corrosion or poor material choice, then sky is the limit.

One 2 3/8th diameter stud comes to mind. Proper torque is .009 to .011 stretch, about 2700 ft pounds if all is new and clean. Used bolts may be 4000 ft # to tighten. I have stalled a 10,000 ft pound hydraulic wrench trying to loosen these, AFTER heating the core (3/8" thru hole for bolt heaters) to ease the stretch. And drilled more than one out bad bad news.

For barrels, most manufactors specify the torque, for a reason. They don't want it loose either, but dont want to destroy it to take it apart.

Me , torque wrench checked with go no go afterwards, machine to .002 plus on the go, gives a .001 to .002 with torque. Check with plastigage if you are paranoid.

 

[Clark]

Re: Barrel Torque?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Mikee Booshay</div><div class="ubbcode-body">Clark, I loosen lots of big nuts and bolts (gas turbines ). One very simple rule is twice the torque to loosen as tighten, unless heat, corrosion or poor material choice, then sky is the limit.

One 2 3/8th diameter stud comes to mind. Proper torque is .009 to .011 stretch, about 2700 ft pounds if all is new and clean. Used bolts may be 4000 ft # to tighten. I have stalled a 10,000 ft pound hydraulic wrench trying to loosen these, AFTER heating the core (3/8" thru hole for bolt heaters) to ease the stretch. And drilled more than one out bad bad news.

For barrels, most manufactors specify the torque, for a reason. They don't want it loose either, but dont want to destroy it to take it apart.

Me , torque wrench checked with go no go afterwards, machine to .002 plus on the go, gives a .001 to .002 with torque. Check with plastigage if you are paranoid. </div></div>

Never heard of plastigage before
http://www.plastigaugeusa.com/how.html
They say it is for measuring clearance.

 

[nashlaw]

Re: Barrel Torque?

Red loctite? Please, no!

I had a Mauser that had been rebarreled and too it to a 'smith of have it changed out. Lots of heat and sweat it took to remove.

 

[oneeyedmac]

Re: Barrel Torque?

If you read Vaughn's book "Rifle Accuracy Facts" he talks about axial preload and barrel-receiver threaded joint motion. In his experiments he found that loctite usually jarred loose after a few shots. I don't know if he specified which loctite formula he was using though. Vaughn also discusses what you'd need to torque your barrel to in order to maintain 10,500 lbs of axial preload. He suggest 250 ft/pounds. I have a torque wrench that'll max out at 250 ft pounds and I've experimented with it. I get nervous about thread failure once I get over 200 foot pounds. Another way of maintaining a consistent axial preload is the use of proper thread lubricant. Vaughn tested motor oil, teflon tape, lanolin and rosin and consistent preload was an issue. I use ARP thread lube as it's been shown to maintain consistent axial preload through it's life span. On a Remington 700 I torque the barrel to between 150 and 175 foot pounds. It won't accidentally come unscrewed.

The basis of the chapter in Vaughn's book is that the barrel moves in the action, especially when hot because the barrel and receiver change temperature at different rates and therefore expand and contract differently. It's an interesting read.

 

[mdavis78102]

Re: Barrel Torque?

Witness marks.
When I get a barreled action back from the smith, I mark the relationship of the barrel to the action. Just tighten the barrel back to align the marks, and you're back to where the smith tightened it to.

 

[RWSGunsmithing]

Re: Barrel Torque?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mdavis78102</div><div class="ubbcode-body">Witness marks.
When I get a barreled action back from the smith, I mark the relationship of the barrel to the action. Just tighten the barrel back to align the marks, and you're back to where the smith tightened it to. </div></div>

That might work for a time or two but if you do this repeatedly I can guantee you that your not getting the same torque setting.

 

[mheckman]

Re: Barrel Torque?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Clark</div><div class="ubbcode-body">Here is a video of me needing 540 foot pounds of torque + Kroil to get 1937 Mosin Nagant receiver off the barrel.

I cleaned it up, lubed it, and put it back on to the same original location marks on barrel and receiver, and it took 200 foot pounds to get it there.</div></div>

A good friend of mine worked at Crane building Navy M1 match rifles. They had a barrel puller that would screw on and index barrels with shoulders .005 short of indexing. That had to be a pretty high torque value.

 

[mdavis78102]

Re: Barrel Torque?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: RWSGunsmithing</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: mdavis78102</div><div class="ubbcode-body">Witness marks.
When I get a barreled action back from the smith, I mark the relationship of the barrel to the action. Just tighten the barrel back to align the marks, and you're back to where the smith tightened it to. </div></div>

That might work for a time or two but if you do this repeatedly I can guantee you that your not getting the same torque setting. </div></div>

The changes in "torque value" will only effect headspacing by the most .001-.0015" unless someome has cut some really sloppy threads. So, an exact torque to me is of little concern. As long as the barrel butts up to the action and doesn't fall off during a match, all is well.
This is barrel number four on the same action that I've used for three seasons now. Two barrels in the same caliber. I have yet to have to make any adjustments to my dies
to compensate for headspace.

 

[seanh]

Re: Barrel Torque?

I've actually done this test on a remingon 700 and savage 110 about 10 years ago. I found that guns shoot better when properly torqued. What you're doing is pre-tensioning the barrel. It helps to dampen the harmonics/whip action of the bbl.

With the Remington I was using, around 70 Lbs did the trick while the Savage was about 60.

I haven't tested this on what I call high quality large diameter barrels...just the factory HB.

There was a muzzle break that incorporated a torquing technique a while back. You'd fit the break on then start shooting. After a few rounds, you'd check your group and tightening a few lbs. You keept going through this process till the groups opened up again.