Barrel Torque

[jesilva]

What effect would a barrel that is minimally torqued to the action versus one that is tightly torqued to the action. Could barrel heat cause problems with a lightly torqued barrel?

 

[OldManTA]

Shooting through a lightly torqued barrel could conceivably cause the barrel to loosen resulting in increased headspace and insufficiently supported/contained cartridge cases. When you fire a round you can generate a peak pressure spike in excess of 60,000 pounds/square inch. If the barrel unscrews significantly you are running a serious risk of catastrophic failure of the cartridge case, destruction of the action and physical harm--severe injury/death--to the shooter.

It has been a long time but if you can get access to a Machinist Handbook, an Engineering Design text or similar you might be able to find the recommended torque for the size of the thread of the barrel shank. Better yet, get an experienced gunsmith to show you how to torque the barrel properly if you insist on taking the barrel out of the action and reinstalling it. THIS IS NOT SOMETHING TO TREAT CASUALLY.
Tom Alves

 

[carlsbad]

As the Old Man said, if the barrel isn't tight enough not to move when you pull the trigger, bad things will happen and it may involve blood and blindness.

That said, barrel threads are usually very high quality and not much torque is required to seat them. Anybody who has ever tried to take a few barrels off the action knows they don't tend to loosen up.

So if by minimally torqued you mean good and wrench tight vs one of the 100+ ft-lb tightened barrels that in my opinion is way overdone, then you should have no problem. If you mean hand tight, you need to tighten it some more.

Here is a thread that may have more than you ever wanted to know about barrel torque.

http://forum.accurateshooter.com/index.php?topic=3842803.45

--Jerry

 

[jesilva]

The barrel was tightened using an action wrench with the barrel clamped into a padded vise. Then tightened until the barrel started slipping in the vise. I have never had a barrel come loose. However, I was interested to know if the heating of the barrel, ie, expansion would cause POI changes if not heavily torqued.

 

[carlsbad]

If you padded a good vise with leather, then you should have gotten the barrel good and tight. However, since I wasn't there, I can't say. There can be a lot of variation in a padded vise.

Doesn't sound like a gunsmith was involved. Was the headspace checked? Does the bolt properly engage the tenon?

--Jerry

 

[Keith Glasscock]

To answer the original question, no, not in my experience.

I get barrels very warm in F-class and my barrel walks the same at 30 ft-lbs as it does at 65. On the other hand, my shoulders are machined so square that there is nearly imperceptible movement as torqued. I have to draw a line with a sharpie to see when it moves. A less-square setup might behave differently.

All barrels walk some due to heating. I have a barrel that consistently puts the CBS 1/2 MOA above the next shot. A cold-bore x is inevitably followed by a 6 o-clock 10 or 9 right at the line. It then walks down really slowly at 1k yards.

I haven't tried freezing barrels yet. Might be a fun experiment.