Page 1 of 1

Krag barrel dimensions

Posted: Mon Jun 28, 2021 12:49 am
by waterman
I have a chance to acquire a couple of barrels that might or might not be intended for US Krag actions. What are the dimensions of the threaded end of the barrel for a Krag. Since they made upgrades, I assume all barrels were mechanically interchangeable. What are the stub dimensions, max & min diameter, stub length, thread pattern (square?), thread pitch?

I've looked in Mallory & Olson, Brophy, and Farmer's Notes. No one ever bothered with any more than an incomplete diagram. I would appreciate any info.

TIA,

Dick LaVen

Re: Krag barrel dimensions

Posted: Mon Jun 28, 2021 3:48 am
by butlersrangers
'waterman' - Frank de Haas gave Krag barrel thread information in his book, "Bolt Action Rifles". I have attached a diagram from his work.

From my experience all U.S. Krag barrels have the same thread dimensions and approach interchangeability.

The breech end of the U.S. barrel began to receive a slight radius at approximately, #218000, in July 1899.

Earlier 'square-cornered' barrels can be slightly beveled with a file, to correctly seat in later actions.
Late barrels, with the 'breech radius', will fit earlier (pre-#218000) actions.

(Also attached, is a photo of Krag threads with the 'square corner' at the breech end).

Re: Krag barrel dimensions

Posted: Mon Jun 28, 2021 1:58 pm
by butlersrangers
Some views of Krag barrel shanks:

#1 - Square corner of earlier barrel breech

#2 - The same barrel, slightly 'beveled', to fit a later Krag action

#3 - A model 1899 carbine barrel with rounded corner

Re: Krag barrel dimensions

Posted: Mon Jun 28, 2021 3:29 pm
by waterman
Thanks very much. Why did the authors of our main sources of information on the Krag fail to include a drawing like that?

Re: Krag barrel dimensions

Posted: Mon Jun 28, 2021 5:11 pm
by butlersrangers
I guess, there is no perfect book. (That is part of the reason gun forums exist).

Different authors have different interests and focus.

At least Frank Mallory came close in the "KRS", second edition.
Note - Mallory places the change, to the 'rounded corner' on the barrel-breech, at #213000, (rather than my 'off the cuff' guess of around #218000).

Re: Krag barrel dimensions

Posted: Mon Jun 28, 2021 6:16 pm
by butlersrangers
IMHO - Frank de Haas wrote about single-shot and bolt-actions from a gunsmith point of view.
He looked at the merits and faults of an action, with the idea of possibly re-purposing the action in a sporting rifle.
The information on barrel shanks and threads in his books seems very accurate and useful.

The ordnance drawing that Mallory used in "KRS", on close scrutiny, is a bit of a mystery.

I am not sure what the two numbers in the area, that I have enclosed in a yellow box, signify?
Also, The 'shoulder' in front of the threads and the barrel contour, (in the chamber area), is not how a Krag barrel actually appears.

A Krag barrel measures, approximately, .980 inches in diameter directly in front of the threads. There is no 'shoulder'.
Frank de Haas accurately depicted the reality of a Krag barrel breech-area.

Re: Krag barrel dimensions

Posted: Tue Jun 29, 2021 2:14 pm
by FredC
I am going to say it is a mystery. The 3 Krags I own are in that 1899 area and none show that shoulder. The numbers are a little smudged and if I read them correctly the taper would be backwards compared to any other rifle I know of.
Wild guessing here, he found an drawing of a prototype and someone who thought of making 2 bearing shoulders like the Mausers. Wild guess #2 drawing is for an intermediate stage of production and the shoulder is later turned down. Wild guess #3 he picked up the wrong drawing maybe for a prototype 03?

For Waterman measuring the distance from the chamber end of the barrel to the sight holes would be a good ID for sorting mystery barrels.

Re: Krag barrel dimensions

Posted: Tue Jun 29, 2021 5:51 pm
by butlersrangers
Fred - I think you are correct about the drawing that Mallory used. It is probably your #2 idea: some type of 'intermediate machining process/instructions', sort of thing.

The Krag barrel was machined to its final contour from an oversize 'tube'. Those odd dimensions could be from some 'datum line' that disappeared during machining?

Finished Krag barrels don't have or need a shoulder.

Re: Krag barrel dimensions

Posted: Wed Jun 30, 2021 2:18 pm
by FredC
Butlersrangers,
I remember a few years ago a similar drawing was posted with a change to the distance to the shoulder on the cartridge. We could not confirm the change had ever been made. If I remember right it was a rather drastic difference. On a similar rimless case it would have been a drastic change in head space, on the rimmed 30/40 there would have been no head space issue but each round fired would have been fire forming a short case to a longer one, not generally the way you get accuracy. I am wondering if that discussion back then was based on the same defective drawing?