Barrel torque vs precision?

[dcali]

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?

There are a few things in his book a guy might quibble with, a mistake or two, and the main thing people seem to have a problem with (myself included) is the chapter on threads. He leaves a lot unexplained, as well. But almost all of what Vaughn wrote is right. It's a very good book.

But he did compete in benchrest, and was a very competent engineer and ballistician. If someone were to repeat his experiments on modern rifles with modern instrumentation, we'd learn a heck of a lot.

 

[RGRobinett]

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.

BUT . . . at least, using a decent torque wrench, one will achieve consistency, which is usually, "not a bad thing". RG

 

[dcali]

BUT . . . at least, using a decent torque wrench, one will achieve consistency, which is usually, "not a bad thing". RG

Right. I may have overstated that a bit.

I still think they’re far less useful than commonly thought. Like +/- 20% or more when it comes to measuring bolt stretch. They’re also useful for people who have not yet developed a feel for torque.

 

[AlNyhus]

This is a Model 70 here for pillar bedding. The barrel is just hand tight in this pic. Notice the factory witness mark on the barrel shank and the corresponding mark on the front of the recoil lug area.

It seems like it would be a s-t-r-e-t-c-h (pun intended) to get there...but when you look at the stamping on the barrel relative to where it should be along the top of the stock, it's where it needs to go.

Good shootin' -Al

 

[M-61]

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

Yes. Important is to re-check the torque after 50-100 miles. Mag style 8 lug wheels seem to be more susceptible to loosening than others. Why? No clue.

 

[M-61]

They’re also useful for people who have not yet developed a feel for torque.

In lieu of using a torque wrench? You can test yourself on this development. It’s usually a nightmare at low inch pound levels. In mid range it depends on the individual. Higher torque is generally terrible.
60 years of this work and I’ll always use a torque wrench. Maybe I’m still working on ‘feel’ but my guess is that ship sailed.

 

[dcali]

In lieu of using a torque wrench? You can test yourself on this development. It’s usually a nightmare at low inch pound levels. In mid range it depends on the individual. Higher torque is generally terrible.
60 years of this work and I’ll always use a torque wrench. Maybe I’m still working on ‘feel’ but my guess is that ship sailed.

The point is that when friction effects have such a dramatic and uncontrollable impact, you don't need a very good feel. Torque wrenches are pretty accurate at measuring torque. They're not very good at measuring bolt stretch. 99% of what shooters do doesn't require this level of care.

 

[M-61]

The point is that when friction effects have such a dramatic and uncontrollable impact, you don't need a very good feel. Torque wrenches are pretty accurate at measuring torque. They're not very good at measuring bolt stretch. 99% of what shooters do doesn't require this level of care.

Agree. When accessibility allows bolt stretch is the preferred (required) method. Not possible or needed here as you said.

 

[Old Navy]

Yes. Important is to re-check the torque after 50-100 miles. Mag style 8 lug wheels seem to be more susceptible to loosening than others. Why? No clue.

Over torqued?

 

[Old Navy]

After reading this thread from the beginning I have decided my Millwright hammer wrench might not be very consistent, or over or under torqued. I ordered a barrel vise last night. I don't really know how to check the torque on my two Savages. I seem to remember years ago it took less force to unscrew something that it did to screw it together. My memory is a little foggy on this. Been 30 years since I turned wrenches for a living. I do remember that we had high pressure water jet cutters that worked at 45K psi day in and day out that never leaked a drop. My son designed some of those systems.

 

[M-61]

Over torqued?

No. I have found them loose. On a number of occasions I have 2500’s or 3500’s come in with two or three studs broken off of the 8.Jacked it up and the whole wheel is wobbling due to loose nuts. Some loose enough to snap the studs off. Never on steel wheels always on some version of a mag.

 

[Bob3700]

This is a Model 70 here for pillar bedding. The barrel is just hand tight in this pic. Notice the factory witness mark on the barrel shank and the corresponding mark on the front of the recoil lug area.

It seems like it would be a s-t-r-e-t-c-h (pun intended) to get there...but when you look at the stamping on the barrel relative to where it should be along the top of the stock, it's where it needs to go.

Good shootin' -Al

Al,
I cannot imagine the amount of torque it will take to match up those witness marks!
Bob

 

[M-61]

I don't really know how to check the torque on my two Savages.

Barrel nut wrench and a torque wrench. As far as “checking” goes well if you want to be sure NOT to let the Barrel or in your case the receiver turn. There goes your head space.
I’m a switch barrel person and I know of some folks who tighten the nut HAND tight only! They seem to be ok.
Me, 50 ft lbs. I do have a witness mark stamped on them so I can at least see if anything has moved for whatever reason. Never have seen one move yet. So that’s all the ‘ checking’ I do. Never a problem.
Although I’ll admit to making myself crazier by wondering if the bullet traveling down a right hand twist barrel imparts a loosening or tightening force in the barrel. I guess that’s why they make aprazolom.

 

[Bob3700]

No. I have found them loose. On a number of occasions I have 2500’s or 3500’s come in with two or three studs broken off of the 8.Jacked it up and the whole wheel is wobbling due to loose nuts. Some loose enough to snap the studs off. Never on steel wheels always on some version of a mag.

M-61,
I would suspect that the heating and cooling of the aluminum wheel vs the steel hub is what causes the loosening. Aluminum having a different expansion rate when heated and then cooled. You see it in electrical wiring where aluminum has been used. Need to go re-tighten the connections every so often,

 

[Bob3700]

I torque the bbls on my LR prone rifles 55-60 ft/lbs and use synthetic moly greese (Mobile 1). Have not had any issues with bbls coming loose.
Bob

 

[Walt Krafft]

A number of years ago, I had a tire going down on my way to work. I made it to the new tire store in town. They fixed the leak, then stripped three nuts and broke two studs torquing the nuts to 160 pounds with a torque wrench. Never been so po'd before or since.

 

[AlNyhus]

Al,
I cannot imagine the amount of torque it will take to match up those witness marks!
Bob

Bob, it might not take too much on this one. The thread fit is very generous and the factory had some sort of sealer on the threads. Rather than a 'sealer' it may like what Howa uses to stop the creep from the bluing salts. -Al

 

[Old Navy]

Barrel nut wrench and a torque wrench. As far as “checking” goes well if you want to be sure NOT to let the Barrel or in your case the receiver turn. There goes your head space.
I’m a switch barrel person and I know of some folks who tighten the nut HAND tight only! They seem to be ok.
Me, 50 ft lbs. I do have a witness mark stamped on them so I can at least see if anything has moved for whatever reason. Never have seen one move yet. So that’s all the ‘ checking’ I do. Never a problem.
Although I’ll admit to making myself crazier by wondering if the bullet traveling down a right hand twist barrel imparts a loosening or tightening force in the barrel. I guess that’s why they make aprazolom.

I am not worrying about changing the headspace. I have a technique for resetting it that works well.

 

[D Coots]

But he did compete in benchrest, and was a very competent engineer and ballistician. If someone were to repeat his experiments on modern rifles with modern instrumentation, we'd learn a heck of a lot.

Thanks for the reply.

Tony Boyer shooting in SR BR didn't write any books on theories, but he has set a record of Hall Of Fame Points attained that will never be surpassed. His book is of more value when shooting knowledge comes into play due to his record. If you want theories buy Vaughn's book. If you want the real world of SR BR buy Boyer's.

I once overheard a conversation Boyer was having with a well known barrel maker and a couple of well known shooters at the Supershoot one year. He listened to their conversation about looking inside a barrel to evaluate the barrels shooting capabilities. When they were done, Boyer said, THERE AIN'T BUT ONE WAY TO TELL IF A BARREL WILL SHOOT.....and he walked off.

Anyone can read about it, all can't do it...Boyer put in the time and thought.

There'll never be another Tony Boyer.

PS...Theory never beat actually doing it when the rubber meets the road.

Later
Dave

 

[Dusty Stevens]

Thanks for the reply.

Tony Boyer shooting in SR BR didn't write any books on theories, but he has set a record of Hall Of Fame Points attained that will never be surpassed. His book is of more value when shooting knowledge comes into play due to his record. If you want theories buy Vaughn's book. If you want the real world of SR BR buy Boyer's.

I once overheard a conversation Boyer was having with a well known barrel maker and a couple of well known shooters at the Supershoot one year. He listened to their conversation about looking inside a barrel to evaluate the barrels shooting capabilities. When they were done, Boyer said, THERE AIN'T BUT ONE WAY TO TELL IF A BARREL WILL SHOOT.....and he walked off.

Anyone can read about it, all can't do it...Boyer put in the time and thought.

There'll never be another Tony Boyer.

PS...Theory never beat actually doing it when the rubber meets the road.

Later
Dave

I bet ole vaughan neck sized that 270 to benchrest standards.