Thought scope was at fault -- Loose Barrel!

[joshb]

All my barrels are done by Bob Green. He does a fantastic job. I torque mine to 40 lbs. I have never had one come loose.

 

[dgeesaman]

I haven’t seen loctite mentioned for barrel retention. Would that make it too difficult to remove the barrel when needed.

With that amount of precision threads, yes. Appropriate torque works very well.

 

[jackieschmidt]

I do mine at 80 ft lb. That is what my gunsmith recommended. Jackie what do you recommend? Thanks.

75 to 80 pound feet is what I use.

That is an arbitrary figure. Keep in mind, in order for a properly installed threaded joint to function properly, it must be placed in tension. I am skeptical that 35 to 40 pound feet of torque places a 1.062 or larger thread in proper tension. The important thing is to insure that the barrel thread actually advances upon one another.

Several things come in to play. The two most obvious are the finish and quality of the threads and the type of lubricant used.

I use Jet Lube, simply because my shop buys it by the case. We use it to coat shafts when we are shrinking large liners on to the shaft.

https://www.grainger.com/product/30...kwcid=AL!2966!3!281698275537!!!g!472123448796!

To insure that your barrel does advance, I bump it up firmly, then with a sharpie pen, put a line connecting the barrel shank to the action. Then tighten until the marks are about 3/32 apart. That is about 80 pound feet.

Years ago, some well known shooters told others that on a Benchrest Rifle, all you had to do was snap it tight by hand. Shooters that believe that have no understanding of how a threaded joint performs in application.

 

[Shooter13]

I got my new gun a few months ago and shot in 2 matches after some range time, never acted right so after the 2nd match I went to the range to shoot and was all over the place so I thought maybe the tuner needed a big twist and noticed the velcro was 90* from vertical! move the barrel to "hand tight" shot a few round and did see some promise, now after torquing the barrel the gun is shooting lights out.

 

[Paw precision]

The mating between barrel and action threads will have anomolies meaning particulates, unvisible burring, and sometimes deviations that are minute from the tooling process in operation. These things can be so subtle that you cant even see it. For that reason i find that a barrel needs to be worked in to assure a proper set. Using lube - go through the process of tightening. Take it bake loose , scrub clean and do it again. The third time once it gets tight then back off and tighten a couple of times. Think of it as a lapping process. Do this with a new barrel and this will help to set the threads to mesh. Doesnt take long and worth it..

 

[4xforfun]

"proper specs"? What's that?? LOLOL Never had a problem. Don't own one of them torque wrench thingies...wouldn't know how to use one. And I'll bet NO ONE changes BBLs more often at a match (600 and 1K) than I do....not to mention here at home when I clean, test, and load develop.

Of course...I have never had a "donut" in my life either.....till this week!!


Tod

 

[Rdlningcltchdmpr]

A tiny tack weld with a tig welder will prevent loosening.☺☺

 

[Texas10]

75 to 80 pound feet is what I use.

That is an arbitrary figure. Keep in mind, in order for a properly installed threaded joint to function properly, it must be placed in tension. I am skeptical that 35 to 40 pound feet of torque places a 1.062 or larger thread in proper tension. The important thing is to insure that the barrel thread actually advances upon one another.

Several things come in to play. The two most obvious are the finish and quality of the threads and the type of lubricant used.

I use Jet Lube, simply because my shop buys it by the case. We use it to coat shafts when we are shrinking large liners on to the shaft.

https://www.grainger.com/product/30...kwcid=AL!2966!3!281698275537!!!g!472123448796!

To insure that your barrel does advance, I bump it up firmly, then with a sharpie pen, put a line connecting the barrel shank to the action. Then tighten until the marks are about 3/32 apart. That is about 80 pound feet.

Years ago, some well known shooters told others that on a Benchrest Rifle, all you had to do was snap it tight by hand. Shooters that believe that have no understanding of how a threaded joint performs in application.

Can you illuminate me on the idea of "advancing". Are you describing stretching? Some high strength bolts have to be stretched to an OAL dimension during torque.

I have read about using lapping paste on tenon threads to bring more of the threads into full contact, but never heard of advancing threads, so I'm ready to learn something new.

 

[jackieschmidt]

Can you illuminate me on the idea of "advancing". Are you describing stretching? Some high strength bolts have to be stretched to an OAL dimension during torque.

I have read about using lapping paste on tenon threads to bring more of the threads into full contact, but never heard of advancing threads, so I'm ready to learn something new.

I put a new barrel on my LV last week, and here are the marks I placed on it and how they appear after torquing.

As I said I bum it up firm, then put the marks in line. I then tighten the action on the barrel until the marks are a little less than 1/8 inch apart.

From past experience, it takes about 75 to 80 pound feet to do this.

This is simply to insure that the threads did advance on one another.