Weird rifling

Paul B. · March 23, 2000, 02:00 PM

I recently picked up a Mauser 98 (1912-61) that had been converted for Chile to 7.62 Nato. It has a two groove barrel with weird rifling. If you look at it head on, one side looks like conventional rifling, but the other side fades into the bore. Looks like an isocolese (sp) triangle. Slugging the bore was no help. Slug came out at .300 on one side and .309 after a quarter turn.
Like I said, it's a weird barrel.
Paul B.

Jim V · March 23, 2000, 08:39 PM

It has an two groove Springfield '06 barrel recontoured, set back and rechambered. It should have 7.62 electric pencile engraved on the chamber as well as a date in the '60's.

------------------
Ne Conjuge Nobiscum
"If there be treachery, let there be jehad!"

Paul B. · March 24, 2000, 02:50 AM

Jim. Thanks. Somehow, I don't think it is a Springfield barrel. It is a full 23.5 inches. If it had been set back, I would think that it would be shorter. The difference is only 3/8's inch. You'd have to set back a full half inch at least to rechamber to .308. I've seen the Springfield two groove barrels, and this one is different. If memory serves, the lands on the Springfield would look almost rectangular with a very shallow "U" on what would be the top, allowing for the curve of the bore. This rifle, if you were again looking head on into the barrel has one high side (the side that "bites" into the bullet to impart spin) but there is no other side. It tapers into the groove and looks like a shallow triangle. I guess I'm not explaining this very well. If I could draw a picture, you could see it right away.
I'll have to take the gun out of the wood tomorrow and see if that marking you mentioned is there. I'll say this though. The rifling is very very shallow. It hardly shows up on the slug.
Again, thanks for the help.
Paul B.

Paul B. · March 24, 2000, 03:35 PM

Jim. Follow up on my previous post. Double checked the barrel length, definitely 23.5 inches. Tore the gun down to action and barrel. No markings on barrel with electric pencil. Rifling kind of reminds me of a description I read a long time ago about a type of rifling used by Charles Newton in some of his early rifles. I think it was him anyway.
Just double checked in a book I haven't looked at in Years. AMERICAN RIFLE DESIGH AND PERFORMANCE by L. R. Wallack. It is similar to newton's parabolic rifling system. A quote,"Realizing that only the driving edge of the lands did any work, Newton eliminated the other edge." Still doesn't tell me anything, but at least I have an idea of who designed the rifling. Wonder why they used it?
Paul B.

[This message has been edited by Paul B. (edited March 24, 2000).]

March 23, 2000, 02:00 PM	#1
Paul B. Senior Member Join Date: March 28, 1999 Location: Tucson, AZ Posts: 3,802	I recently picked up a Mauser 98 (1912-61) that had been converted for Chile to 7.62 Nato. It has a two groove barrel with weird rifling. If you look at it head on, one side looks like conventional rifling, but the other side fades into the bore. Looks like an isocolese (sp) triangle. Slugging the bore was no help. Slug came out at .300 on one side and .309 after a quarter turn. Like I said, it's a weird barrel. Paul B.

March 23, 2000, 08:39 PM	#2
Jim V Senior Member Join Date: January 31, 1999 Location: SE Michigan - USA Posts: 4,038	It has an two groove Springfield '06 barrel recontoured, set back and rechambered. It should have 7.62 electric pencile engraved on the chamber as well as a date in the '60's. ------------------ *Ne Conjuge Nobiscum* "If there be treachery, let there be jehad!"

March 24, 2000, 02:50 AM	#3
Paul B. Senior Member Join Date: March 28, 1999 Location: Tucson, AZ Posts: 3,802	Jim. Thanks. Somehow, I don't think it is a Springfield barrel. It is a full 23.5 inches. If it had been set back, I would think that it would be shorter. The difference is only 3/8's inch. You'd have to set back a full half inch at least to rechamber to .308. I've seen the Springfield two groove barrels, and this one is different. If memory serves, the lands on the Springfield would look almost rectangular with a very shallow "U" on what would be the top, allowing for the curve of the bore. This rifle, if you were again looking head on into the barrel has one high side (the side that "bites" into the bullet to impart spin) but there is no other side. It tapers into the groove and looks like a shallow triangle. I guess I'm not explaining this very well. If I could draw a picture, you could see it right away. I'll have to take the gun out of the wood tomorrow and see if that marking you mentioned is there. I'll say this though. The rifling is very very shallow. It hardly shows up on the slug. Again, thanks for the help. Paul B.

March 24, 2000, 03:35 PM	#4
Paul B. Senior Member Join Date: March 28, 1999 Location: Tucson, AZ Posts: 3,802	Jim. Follow up on my previous post. Double checked the barrel length, definitely 23.5 inches. Tore the gun down to action and barrel. No markings on barrel with electric pencil. Rifling kind of reminds me of a description I read a long time ago about a type of rifling used by Charles Newton in some of his early rifles. I think it was him anyway. Just double checked in a book I haven't looked at in Years. AMERICAN RIFLE DESIGH AND PERFORMANCE by L. R. Wallack. It is similar to newton's parabolic rifling system. A quote,"Realizing that only the driving edge of the lands did any work, Newton eliminated the other edge." Still doesn't tell me anything, but at least I have an idea of who designed the rifling. Wonder why they used it? Paul B. [This message has been edited by Paul B. (edited March 24, 2000).]