Barrel tension?

[MagnumManiac]

Hey all,
Have a question about barrel tension.
What do you guys think of the theory that a less than desirable tension will result in varying harmonic vibration?
I have switch barrel rifles, I do not torque my barrels on, I simply spin them on until the snap closed, grab the barrel and tighten by hand. I've never experienced any problems, none of my barrels have come loose, in fact, after 200 rounds, they appear tighter to remove.

Do you think this barrel harmonics theory has any validity?
What do you torque your permanent barrels to?
I simply tighten by hand, then give a 1/4 turn past that with the torque wrench, I do not 'torque' to a setting.

Cheers.
gun)

 

[Darkker]

Harmonics are real, and I can see them in the output from the Pressure Trace.
That said, I haven't been able to "see" that more or less is anything better it worse; simply different.

 

[FearNoWind]

Barrel harmonics is a factor of the barrels movement (bending moment) throughout it's length, Obviously a barrel that isn't properly seated in the action is going to be a problem but once it's secured the affect of harmonic influences appear as the projectile moves through the bore.

https://www.google.com/search?q=rif...pdPKAhVKwGMKHSFDDbEQ_AUICSgD&biw=1231&bih=895

http://www.geoffrey-kolbe.com/articles/rimfire_accuracy/tuning_a_barrel.htm

 

[Gene]

That is why they make barrel tuners - they help find the right harmonics.

I have a barrel vise and do what I have seen my smith do - tighten by hand, then insert a side entry wrench in the action and smack the wrench several times with a 2 lb. hammer.

 

[Canadian Bushman]

Hey all,
Have a question about barrel tension.
What do you guys think of the theory that a less than desirable tension will result in varying harmonic vibration?
I have switch barrel rifles, I do not torque my barrels on, I simply spin them on until the snap closed, grab the barrel and tighten by hand. I've never experienced any problems, none of my barrels have come loose, in fact, after 200 rounds, they appear tighter to remove.

Do you think this barrel harmonics theory has any validity?
What do you torque your permanent barrels to?
I simply tighten by hand, then give a 1/4 turn past that with the torque wrench, I do not 'torque' to a setting.

Cheers.
gun)

Do you ever notice a change in accuracy from immediately after you put one on to right before you take one off?



Next time you switch a barrel and tighten by hand could you do a small experiment?

Just draw a line across the action barrel joint and see how much it tightens from shooting?

Maybe check the torque with a wrench when you break it loose?

Id be real curious to know where it settles.

 

[Hired Gun]

I have always believed on barrels it's better to be too tight than a little loose. Are you sure about 1/4 turn? 90 degrees on a 16 TPI you would be crushing (.0625"/360 degrees)90 = .0156". of steel somewhere. Most likely the threads distorting.

On one of my barrel fits to get to 100+ foot pounds I can only move the joint 20 degrees and that changes headspace about .001". Only another couple degrees takes 250 foot pounds.

Vanguard rifles have the tightest barrels in the industry. I never measured how far one has to move once they touch to get back to the reference mark. The are known to shoot pretty good right out of the box. I wonder if that isn't part of their design?

 

[Edd]

What kind of lubricant do you guys use on your barrel threads?

 

[Hired Gun]

Just a dab of this is all we use.

 

[Canadian Bushman]

+1

I use a copper based anti-seize from permatex.

 

[Edd]

I don't have any of that stuff. I have got plenty of Dow Molykote P37. I was considering using it. Anyone think that would be a bad idea?

http://www.swantek.com/html/molykote_p37.pdf

 

[MagnumManiac]

Do you ever notice a change in accuracy from immediately after you put one on to right before you take one off?



Next time you switch a barrel and tighten by hand could you do a small experiment?

Just draw a line across the action barrel joint and see how much it tightens from shooting?

Maybe check the torque with a wrench when you break it loose?

Id be real curious to know where it settles.

First off, sorry for not responding earlier, been away.
There is no discernable difference in accuracy, I have removed a barrel and put it back on during a match due to a stuck case, accuracy never changed. I also cannot see any change in the barrel fit after 200 rounds, it appears tighter to remove, but, there is no evidence the barrel is turning in the action. All my rifles have witness marks, and I have often looked to see if the barrel moves, as far as I can tell, they don't.
Have checked with a torque wrench, no barrel has ever needed more than 10ft/lbs to loosen.
I used to torque, but, no matter how much force was used, due to the positive stop of the shoulder, did the barrel go in anymore.

Cheers.
gun)

 

[MagnumManiac]

I have always believed on barrels it's better to be too tight than a little loose. Are you sure about 1/4 turn? 90 degrees on a 16 TPI you would be crushing (.0625"/360 degrees)90 = .0156". of steel somewhere. Most likely the threads distorting.

On one of my barrel fits to get to 100+ foot pounds I can only move the joint 20 degrees and that changes headspace about .001". Only another couple degrees takes 250 foot pounds.

Vanguard rifles have the tightest barrels in the industry. I never measured how far one has to move once they touch to get back to the reference mark. The are known to shoot pretty good right out of the box. I wonder if that isn't part of their design?

Yes, I think you're right, it is barely 1/16 of a turn to TORQUE the barrel, but roughly a quarter turn to get it tight prior to torquing it down.
As I said, I don't torque my barrels anymore, my barrel vice and wrench sit gathering dust. It is not designed for excessive torquing of permanent barrels, maxes out at around 25ft/lbs before the barrel slips.

Cheers.
gun)

 

[MagnumManiac]

What kind of lubricant do you guys use on your barrel threads?

I use Loctite nickel anti-seize every time I change out a barrel.
I use the nickel because I was told it helps to stop galling on stainless threads better than copper.

Cheers.
gun)

 

[Hired Gun]

I used to use the nickel but as an experiment I tried the copper stick and discovered it doesn't bleed out of the barrel joint as bad when I gas out a barreled action for Cerakote. The joint still pushes out some lube with copper but only a fraction as much as the silver stuff. An interesting note is some actions contain oil deep in the castings that takes a couple acetone soak/heat cycles to get it prepped proper for Cerakote so even steel actions fitted to stainless barrels dry can still bleed oil.

Barring Cerakote prep I would probably go back to the nickel formula. The sticks are the only way to use any of them.

Never fit stainless to a stainless action dry. I have never galled a barrel but have seen lots of stainless fasteners galled up and broken from being assembled dry.