Undersized Barrel Thread

[gzig5]

I've got a nice low mileage barrel that came off another action. It headspaces correctly on my action, but the pitch diameter of the barrel thread is 2-3 thou undersized compared to mine. So it goes on easily with more radial wobble than you'd want, but it locks up nicely without any squish. Essentially you snap it up against the shoulder and it stops abruptly. I don't think there is any issue with thread strength, and my brain tells me that the thread will be self centering when it is tightened up. But I wonder if there is any benefit to putting a couple wraps of Teflon tape (or other material?) on the thread to take up some of that slack and better center the barrel in the action as it comes in? I'd rather not cut and re-thread the tenon because though I have the go gage, I don't have a 6ppc reamer. Use will be for some paper punching and varmints. I don't plan on any BR competition. Thoughts? I will graciously endure the requisite gun plumber comments.

 

[Kleinfeldt]

Is it possible to align with a pin before you tighten ?

 

[BobbyBailey]

Greg,
What is the dia. of the thread you are looking for vs the thread you have.
A Rem. is 1.062 but most people cut them to anywhere from 1.050 to 1.060. So, a couple of thou. might not be that big of a deal. Now, you might not being dealing with a Rem. but, I used it as an example. Savages are also 1.062 but, are routinely cut to 1.050. Just another example.

Bobby

 

[RWO]

Forgetaboutit. There is nothing wrong with the barrel thread. Torque it to 75-90ftlbs. and go shooting.

RWO

 

[MilGunsmith]

Tighten it on and go shoot it.

 

[gzig5]

Bobby,
It’s a Panda. Don’t have the numbers in front of me but I measured about 2.5 thou less than the min recommended PD as stated by Kelbly’s using thread wires. Like I said it locks up nice but it’s a little looser than you’d prefer. I’ll be turning a spud and then a new barrel to fit the action soon and will then know what the action will accept on the top end of the tolerance. Sounds like I probably need not worry about it on this barrel but I’ll aim for a closer fit on the new Krieger.
Greg

 

[GGaskill]

A friend of mine screwed up a thread job on a rebarrel (for himself) by waiting too long to check the thread with the action. We tried using thin shim stock to take up the slop and it has worked well. The barrel has not moved and the headspace is still the same after much use.

He shoots long range with this rifle and is very successful.

 

[[486]]

Ever taken apart an enfield rifle?

They've got the threads set up so it just barely catches on the peaks of the threads, probably 20% engagement or worse.

They jam them on there to about a thousand ft/lb and they seem to do okay. Had to use a parting tool to take the tightness off in order to get it to budge, had the barrel in aluminum blocks with the 40 ton press doing all it could to grip the barrel.

Was setting back a barrel a few threads to rechamber to 54R, and just about pooped when I saw how floppy the fit was.

 

[Danny VanVoorn]

I wouldn't try and wrap it with anything, just use as is or not. If you wrap it with something and it is thicker in one area than others it will tighten off center. If the barrel thread is centered it will tighten on center in the receiver naturally.
Dan

 

[tdmidget]

Is it just me or wouldn't it be a good idea to figure out how this came about?

 

[Anthony]

As others have said I would use as is. I don't care for the teflon tape idea, it is too slippery and may let the barrel slowly loosen. I would consider a little low to medium strength thread locker. Tighten as you normally would and go shooting.

 

[gzig5]

Is it just me or wouldn't it be a good idea to figure out how this came about?

I think it's just you. As stated, it's a used barrel from another rifle chambered by an unknown 3rd party. What's to figure out? It may of fit that action fine, but it measures under the action maker's published spec.


The teflon tape is likely to shred once it is spun all the way in, so I think I'll leave it be and let the thread center itself and see how it goes.

 

[BobbyBailey]

Greg,
With what you've said, I can't see where you will have a problem. Over the years I've pulled apart several factory barrels that had pretty sloppy threads.
It's not the level of work we do nor is it the level you do, but it's not uncommon on a lot of factory rifles. A lot of the barrels had some thread locker I'm sure to take up the slop.
You'll be fine.

 

[300sniper]

I'd run it as is.

 

[WF Custom]

When I first started chambering barrels years ago, I thought a nice "micrometer" fit was a sign of superior workmanship. As the years went by I discovered that using the minimum spec for thread pitch saved you and the barrel owner a lot of potential angst. As I'm sure you know std thread form requires square mating surfaces inline with the threads much more then 100% thread contact. "Snap it against the shoulder and it stops" A small drop of light oil on the barrel shoulder can help with the centering, but screw it on and see if it shoots!
Regards,
Greg

 

[john.k]

In my experience,a barrel/action fit that is a two hand screw on,will end up sloppy if it is screwed up and unscrewed half a dozen times....I always coat the threads with never seize,after a few bad experiences over the years..........I believe Rossi get their barrels to line up by the use of loose threads and Loctite.

 

[tobnpr]

I spoke with Dave Manson on this subject (asked his opinion on a nearly identical scenario as this) suffice to say thread fit isn't as critical as the receiver and barrel shoulders mating at precisely 90 degrees is what I was told- and I'll take his advice to the bank any day.

 

[WF Custom]

"A few bad experiences over the years" is exactly why I went to a min pitch spec on barrel threads. Been there done that won't go there anymore!