Correcting Barrel Indexing

Sporterized and unofficial modified Krags
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butlersrangers
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Location: Below the Bridge, Michigan

Correcting Barrel Indexing

Post by butlersrangers » Tue Jan 12, 2021 6:38 am

Some time ago, I put a 'sportered' Krag carbine barrel on a stripped model 1898 action. This resulted in a practical short Krag, assembled from accumulated loose parts.

One thing that bothered me about the outcome was that the barrel index-mark ended up about 2 to 3 degrees "North" of the action index-mark.
A little file work widened the barrel's extractor-notch and solved the problem of the extractor tip catching or rubbing.

It was a safe parts gun and things worked, but, it was irritating that the rear-sight was canted a few degrees to the left. This also created position problems and friction at the hand-guard sight opening.

The other day, I noticed 'head-space' with this Krag was a bit tight. The bolt-face put slight rub marks on the base of old Remington factory ammo.

I looked into possible corrective action. The 'Cast Bullets' forum had some discussion of correcting the same type of "over indexing" problem on 1903 Springfield rifles.

A very practical and frequently suggested remedy was carefully 'dimpling' the barrel breech-face, with a center-punch, to raise some metal.
The disrupted metal adds a few thousandths of 'depth' for earlier contact with the flange inside the action 'ring'.

I gave this a try on the Krag barrel and also applied some 'blue' Loctite to the threads. The action was hand tightened onto the barrel and came to a 'stop' about 4 or 5 degrees short of the mark.
Judicious force on a barrel-wrench allowed a 'crush fit' with the extractor-notch and index marks in great alignment.

The sights are now nice and level.
Attachments
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barrel fix-3.jpg
barrel fix-3.jpg (331.1 KiB) Viewed 105 times
Last edited by butlersrangers on Tue Jan 12, 2021 4:19 pm, edited 3 times in total.

FredC
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Location: Dewees Texas

Re: Correcting Barrel Indexing

Post by FredC » Tue Jan 12, 2021 3:23 pm

The making of all these parts and getting them 100% interchangeable was pushing the technology of the time. it would even be hard today to get the timing that good. I only have experience with 2 rifles so far mine and the member I lent my tools to. Mine was a piece of cake and the torque to unscrew it was at the bottom end of the practical range. The member that borrowed my tools had a very hard time unscrewing his. So at the arsenal they improvised with the tightness. After a barrel or receiver is made you hate to throw it away because it is ever so slightly out of tolerance.

Your solution is very much like what my dad would have done. And I mean that is the best possible way. I watched him repair lawn mowers for the local Western Auto store (you remember them?) when I was a kid. After I started working in a machine shop he told me some of hit tricks that I did not catch back then. Knurling a piston to enlarge it with a round end punch and a hammer was one of his tricks. For next time you could sand or hone the surface before putting it together. The material will still be displaced around the punch marks but the sharp edges will not be there to mar the receiver. Practical solution, I like it better than a beer can shim.

Added thought:
Now I see the method to your madness, the spot skipped is visible in the locking lug recess. A mark there would have done no good anyway.

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butlersrangers
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Re: Correcting Barrel Indexing

Post by butlersrangers » Tue Jan 12, 2021 4:10 pm

Hey, I've got $45 invested in that old Krag carbine barrel!
The bore finish has gotten better after each Range session and cleaning.

I wasn't about to deface that original 'steel lot-number', visible at the 'locking-lug' recess.
Patina and color on the barrel-breech made it pretty obvious where contact is made and punch marks should go.

(BTW - I did protect the chamber mouth, by inserting an empty cartridge-case, during the punch/peening process).

FredC
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Re: Correcting Barrel Indexing

Post by FredC » Tue Jan 12, 2021 4:21 pm

"(BTW - I did protect the chamber mouth, by inserting an empty cartridge-case, during the punch/peening process)." Quote

You are giving away your secrets.

Oh, that is what a forum is about!

todd444
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Location: windber, pa

Re: Correcting Barrel Indexing

Post by todd444 » Tue Jan 12, 2021 5:38 pm

ssssssshhhhhhhhhhh!!!!!!!!!! if you don't tell anyone, then i won't!!! :D
The clock of communism has stopped striking. But its concrete building has not yet come crashing down. For that reason, instead of freeing ourselves, we must try to save ourselves from being crushed by its rubble.
Aleksandr Solzhenitsyn

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Local Boy
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Re: Correcting Barrel Indexing

Post by Local Boy » Tue Jan 12, 2021 6:36 pm

GREAT solution to a barrel alignment problem BR!

I have a similar problem with a Model 1917 Eddystone..

I've had to correct the issue by tapping the front sight all the way to the left to the point of almost touching the left side of the front sight wing guard.

Actually, I could probably use the left side of the wing guard as my front sight. :roll:

Think I'll steal your idea but don't worry...you secret is safe with me. 8-)

BTW: Before some smarty pants corrects me its: U.S. Rifle .30 Model of 1917

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carbon outlaw
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Re: Correcting Barrel Indexing

Post by carbon outlaw » Tue Jan 12, 2021 6:57 pm

one solution is to buy brass shim stock ... the brass shim stock I use comes in 1 thousand inch on up ... It is easy to cut out and you put in on your barrel and screw it in and add shims ... Now the hard part what if your head space is off ... blaaaa ... what I do is I have a hole drawer full of bolt handles and some times you can find one that works ,\... although Krag precision is so close our lucky to to find one or two thousands difference ...

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carbon outlaw
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Re: Correcting Barrel Indexing

Post by carbon outlaw » Tue Jan 12, 2021 7:10 pm

my bolt handle collection ..
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FredC
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Re: Correcting Barrel Indexing

Post by FredC » Tue Jan 12, 2021 8:07 pm

LocalBoy, a shim in the Krag while not impossible is problematic with the cut out for the extractor slot. There is a risk of getting a partial double thickness with a fold or something. I am with Carbon Outlaw that for the 1917 Eddystone :-) a shim is a better solution than dimpling. If cut accurately there will be little chance of getting a double thickness anywhere. It would not be heresy to use plastic shim stock either. Hardinge used to sell sets of color coded shims for correcting tool center line with ground cutting tools for use on their HC chuckers. I have a set of them I have been using for 30+ years. Between 2 flat surfaces they do not compress or ooze out. Plastic shim material would be easier to cut with an Exacto or Excel knife.

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Local Boy
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Re: Correcting Barrel Indexing

Post by Local Boy » Tue Jan 12, 2021 9:42 pm

Hmmm...things to think about?

Thanks FreadC!!!

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