Barrel Joint Movement??

DenisA · Post by **DenisA** » Mon Dec 30, 2013 3:55 pm

I've been reading a book recommended to me called Rifle Accuracy Facts by Harold R. Vaughn. A subject thats bouncing around in my head is barrel joint movement.
Apparantly it can shift randomly after any number of shots, allowing great accuracy while its stable but significant POI change when it does move.
Vaughns testing (on his rifle) using different lubricants, loctites and grades of recoil lug found that 250 ft/lbs of torque gave most consistant results.

My concerns are:

I've never toqued my barrels and know a lot of people that don't and don't seem to need to. Just make them tight.

I get excellent accuracy out of my rifles, but I do get POI changes which have returned to the original POI after a few shots. I've always wondered why, blamed wind calls and/or focused more intesly on my technique or my handloading which is comprehensive.
(its not the scope) NF and March.

I shoot Savages and still utilise the barrel nut system which means theres no barrel shoulder to square up against the action. Im wondering if a barrel nut system is any more or less subject to this issue..

I'm going to start torquing my nuts :oops:

, but I'm interested if anyone else has any experience with this effect and can elaborate?

Cheers, Denis.

DenisA · Post by **DenisA** » Mon Dec 30, 2013 4:09 pm

Also, whos read and like or dislikes this book?

DaveMc · Post by **DaveMc** » Mon Dec 30, 2013 5:01 pm

I love that book but if you read it too much you will start to wonder how we shoot well at all.

A lot of atmospheric changes (mirage and heat etc) will move you around and bring you back. Some ranges are notoriously bad for it.

DenisA · Post by **DenisA** » Mon Dec 30, 2013 5:08 pm

DaveMc wrote:I love that book but if you read it too much you will start to wonder how we shoot well at all.

A lot of atmospheric changes (mirage and heat etc) will move you around and bring you back. Some ranges are notoriously bad for it.

LMAO................ simple but effective answer.

johnk · Post by **johnk** » Mon Dec 30, 2013 5:25 pm

Additionally, I suspect that since that book was written, there has been significant work done on the dimensions of tenons & in some instances, the quality of barrel threading.

DenisA · Post by **DenisA** » Mon Dec 30, 2013 5:32 pm

Good point John. Though the tenon threads on the barrels I have are not as snug fitting as I would have thought they could be.

I have read some reviews on Rifle Accuracy Facts that suggest it may be a little predated in areas.

mike H · Post by **mike H** » Mon Dec 30, 2013 7:22 pm

With 250 foot pounds tension methinks you will need a good barrel vice.:

DenisA · Post by **DenisA** » Mon Dec 30, 2013 7:29 pm

Agreed Mike, I won't be going anywhere near that tight. The author said at that tension it felt like the threads were going to giveway :shock:

I'll try 50 and see how that feels for a start.

Matt P · Post by **Matt P** » Mon Dec 30, 2013 7:58 pm

FWIW, I torque all barrels to 120 Foot/pound, this one area the Barnard has an advantage over it's rivals when barrels are fitted correctly.
Matt P

DenisA · Post by **DenisA** » Mon Dec 30, 2013 8:03 pm

Matt P wrote:FWIW, I torque all barrels to 120 Foot/pound, this one area the Barnard has an advantage over it's rivals when barrels are fitted correctly.
Matt P

Thanks for the input Matt. I'll work on that then.

When you cut tenon threads, do you make them quite a prcise fit to the action?
If you've got the tenon wound 7/8 of the way in to the action, can the barrel be wiggled at all?

johnk · Post by **johnk** » Mon Dec 30, 2013 8:13 pm

I've never had an issue with 80 ft/pounds on the Millenniums. Once lubed with antigall, I generally need to lean on them (sometimes seriously) to break them out.

Matt P · Post by **Matt P** » Mon Dec 30, 2013 8:17 pm

I like them to have minimal "movement", it's very hard to explain, but I'm not convinced it makes a difference, recently I rechambered a very old and tired 6mm barrel for myself, this barrel has done 6000 plus rounds in 3 actions and 4 different chambers but has always shot very well, anyway I rechambered it again, this time in Dasher, it's quite short and didn't want to lose anymore length so I chased the the thread and moved the chamber forward about 8mm, while chasing the thread it ended up very loose (unacceptably loose for a customer) but I put it together anyway not expecting to much but does this thing shoot !!! back to 600m it's my No 1 barrel.
The more we learn the less we know.
Matt P

DaveMc · Post by **DaveMc** » Tue Dec 31, 2013 9:11 am

I believe you can sometimes get an indication of barrel joint movement. I was asked to help someone develop a load for a rifle and when we ran it through its paces it was getting excessive bolt lift pressure very early. After ripping off the barrel it was obvious it was a very poor fit (missing half the threads due to a scope mount screw binding on thread in previous life). I believe this heavy bolt lift was actually the tenon joint stretching (case expanding) and then coming back after pressure dissipated. It still shot very well but could not be pushed. No case head issues - just case stretch. I had the feeling there was something amiss so checked by removing barrel and then politely suggested he should have it seen to by a gunsmith :shock:

ecomeat · Post by **ecomeat** » Tue Dec 31, 2013 12:14 pm

Tony Boyer is one of the best ever Bench Rest shooters in the US and in his book "The Book of Rifle Accuracy" he says he tightens to 50 ft/lbs.

Phil Jones explained it to me, along the lines of "it will just snap to a position, where you know that it's metal face meeting metal face and it doesn't want to go any tighter"...... And that that is all it needs.

Tony Boyer explains it as [b]"when the face of the action hits the shoulder of the barrel it should feel like it comes to a sudden stop. Same as when two perfectly parallel faces hit each other."[/b]
I guess it isn't like that with a Savage nut ?

Denis,
I have read Vaughn's book cover to cover a couple of times too, and just like Dave said, it scared the pants off me, left me wondering how we ever hit anything !!

johnk · Post by **johnk** » Tue Dec 31, 2013 12:34 pm

I recall when Nev Madden started gunsmithing commercially. He was the talk of the town - the person whose threading was so precise that the slop would stop when you'd run the barrel in just a few threads. As an innocent, I had my little Sako L461 rebarrelled in the late sixties. I pulled that tube out recently & found that the threading was so rough that it might have been done with a pipe tap.