Barrel torque vs precision?

[jackieschmidt]

I could care less what Savage, Remington, or any other says about how tight to install a barrel on a typical bolt action tenon. I use around 80 ft pounds, and the rifles shoot great.

For these size threads, 80 ft pounds is really not much. It might seem like a lot, until you look at the torque specs on a 1/2 inch main bearing bolt on a big block Chevy.

Threads work in the function of securing a joint by being placed in tension. That means you have to actually stretch the metal in order to accomplish this. This amount of yield in the material is so slight on a barrel tenon that it would be difficult to qualify. But if the barrel joint has zero movement during the firing cycle, it is in tension.
I personally think 40 is too light. But if the Rifle shoots up to your expectations, who am I to argue with that.

 

[M-61]

There was a video a long time ago where the president of Savage said it. It was probably back in 2012 or earlier.

I’ll try to find it unless you know where to search.
Thanks

 

[rijndael]

I’ll try to find it unless you know where to search.
Thanks

I did a quick look but can't find it anymore.

 

[Dave M.]

Speedy recommends 100ft-lbs

 

[JFrank]

I’m not sure if a guy could advance the threads enough to make any difference in tune, but a different receiver with a different ignition will certainly change the tune.
I use 60# to torque the barrel on my Bat B.

 

[jamesdmock]

While changing barrels at the SS one year, Dwight Scott walked by and I asked him if he thought that my torque was sufficient. He told me that he preferred a tighter fit. I asked about ft lbs and he said that that depends on several things like lube and thread quality. However, he said that he would not be afraid of 100 ft lbs. I was somewhat surprised, but have used more torque since then.

 

[urbanrifleman]

I recently 'upgraded' the action to a Mack Bros Evo II on my Rem 700 .308 Win Remage & torqued the barrel to 50 ft lbs. I believe on the Rem 700 action I had it at 40 ft lbs... anyway. Same barrel.. It seems to shoot my 110gr (Note 1) reloads about the same, but doesn't seem to shoot the 175SMK FGMM near as well, and not too happy with my 175SMK reloads either (1"+ at 100yds.). Does barrel torque have an effect on tuning?

Note: only shot 6 of them as my stock is LOW and my new Varget is much different than my old; over 100 fps for same load, and precision seems not as good with the new stuff.

Got the new action for the 308 so I could use the Rem 700 action on a 243 build.

I suspect it's something else. Like the 100 fps.

 

[SKWERLZ]

Isn’t it tactical ops that runs a butt load of torque on their barrels?
I think they use a modified buttress thread as well.

I’ve ran anything from snap tight on smaller cartridges to 100ft lbs on my bigger magnums.

 

[rijndael]

Isn’t it tactical ops that runs a butt load of torque on their barrels?

Yes. I've read it's 220-280 ft./lbs.
https://www.snipershide.com/shootin...ig-deal-with-tacops-rifle.168727/post-2959024

 

[jackieschmidt]

Yes. I've read it's 220-280 ft./lbs.
https://www.snipershide.com/shootin...ig-deal-with-tacops-rifle.168727/post-2959024

That’s an asinine marketing ploy to sell rifles to guys who have fake plastic winches bolted to the front of their trucks so people will think they “off-road”.

 

[swd]

Re tune the rifle for the new lot of powder. If the barrel is in reasonably tight it’s not barrel torque. Check action screws for touching things they shouldn’t, check bedding, check the trigger/safety for touching the stock and trigger guard, does the mag jam hard against the action? etc etc.. When you change something as major as an action there are lots of little things that need to be checked. It’s just like building a new rifle. Let alone the 100+fps change from the Varget lot change..

 

[urbanrifleman]

Re tune the rifle for the new lot of powder. If the barrel is in reasonably tight it’s not barrel torque. Check action screws for touching things they shouldn’t, check bedding, check the trigger/safety for touching the stock and trigger guard, does the mag jam hard against the action? etc etc.. When you change something as major as an action there are lots of little things that need to be checked. It’s just like building a new rifle. Let alone the 100+fps change from the Varget lot change..

Yah, I'm thinking it MIGHT be the powder.

 

[Jayplace]

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.

 

[Old Navy]

That’s an asinine marketing ploy to sell rifles to guys who have fake plastic winches bolted to the front of their trucks so people will think they “off-road”.

You better have a big wrench and a lot of lead in your butt for that much torque.

 

[Dusty Stevens]

The actual torque for a barrel joint is well over 300lbft if you go into actual fastener engineering for that size

 

[Old Navy]

The actual torque for a barrel joint is well over 300lbft if you go into actual fastener engineering for that size

No thanks. Don't need to know any more that what my torque wrench is set at.

 

[Lynn Brase]

With thread/in at 16, 18, 20. Would you tourqe 20 tpi somewhat lower than 18 tpi and 18 a bit less than 16 tpi.?

 

[Dusty Stevens]

With thread/in at 16, 18, 20. Would you tourqe 20 tpi somewhat lower than 18 tpi and 18 a bit less than 16 tpi.?

Yes

 

[Keith Glasscock]

The actual torque for a barrel joint is well over 300lbft if you go into actual fastener engineering for that size

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...

 

[WSnyder]

For his system the barrel tenon was turned smaller by enough so that there was a piece over it that was threaded to match the action on its outside, and for the tenon on the inside. This insert was shorter than the action threads so that it could be adjusted in and out so that the location of the thread start could be changed. I believe his tests showed an effect on accuracy from different index positions of the same barrel, but it has been a long time since I read about it.

Although that would be a fun experiment, the amount of rotation caused by torquing a barrel 40 ft/lbs vs 50 ft/lbs is negligible.

Gene used a differentially threaded bushing so he could index the barrel 360°. If I remember correctly tests in his tunnel seemed to show an accuracy preference to indicate the muzzle down. I’m sure I could dig up old posts off BR Central about it.

His original experiments were in a Panda or Viper action I believe in 6PPC. The biggest issue was the reduced tenon diameter on the barrel allowed too much expansion which caused a big clicker issue which could not be fixed with the high PPC pressures so he eventually abandoned that. I was not aware of a .223 that he did but that would make more sense for testing with a thicker wall to handle pressures better than the PPC.