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Title: Shallow rifling considerations 


After a pre-shooting cleaning session with my 'new' Krag, I notice that there seems to be considerably shallower rifling near the breech than there was when I started. I guess there was some crud built up on the lands and now it's gone. It looks like for about the first 2" of bore the lands aren't much more than speed bumps, then they get a little sharper down the line. My concern is the effect that this will have on the bullet as it goes down the bore. Will this cause some stripping to occur before engraving, thus allowing wider grooves to be cut on the bullet and gas cutting to happen? If so, is there anything I can do in loading/casting to reduce this possibility? Will this have a big effect on accuracy? Thanks, Stan

StanDahl posted on 02/15/2004 02:38:21

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After a pre-shooting cleaning session with my 'new' Krag, I notice that there seems to be considerably shallower rifling near the breech than there was when I started. I guess there was some crud built up on the lands and now it's gone. It looks like for about the first 2" of bore the lands aren't much more than speed bumps, then they get a little sharper down the line. My concern is the effect that this will have on the bullet as it goes down the bore. Will this cause some stripping to occur before engraving, thus allowing wider grooves to be cut on the bullet and gas cutting to happen? If so, is there anything I can do in loading/casting to reduce this possibility? Will this have a big effect on accuracy? Thanks, Stan

StanDahl posted on 02/15/2004 02:38:22

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"It looks like for about the first 2" of bore the lands aren't much more than speed bumps, then they get a little sharper down the line"

........The Krag had a fairly long throat/leade as a consequence of it's long blunt 220gr boolit. Pretty much like the 7x57 Mauser's. One of Lyman/Ideal's first bullet designs to take GC's was the 311284 which was concieved specificly for 30-40 Krag 600 yard shooting. It is certainly possible if your rifle has seen a lot of use that the leade has been eroded or worn deeper.

"Will this cause some stripping to occur before engraving, thus allowing wider grooves to be cut on the bullet and gas cutting to happen?"

........Possibly.

"Will this have a big effect on accuracy?"

........If it does happen, then yes. But the word 'Big' has to be qualified. Possibly you can just say, "Will this have AN effect on accuracy?"

"If so, is there anything I can do in loading/casting to reduce this possibility?"

........I like this post as I can speak with direct experience and not just a seat of the pants thing . In mentioning the 7x57 cartridge earlier it was with using one I have as an example. Most any military 7x57 has a generous throat and leade as they were also designed for a heavy RN slug of 173 to 175gr weight.

A gentle leade is actually a good thing with a cast boolit, but not if it ends somewhere up under the rear sight area. I have a 1895 Chilean Mauser infantry (29" bbl) which was apparently well taken care of as atthe muzzle the lands are in good shape and not oddly worn from thoughtless cleaning. On the other hand, the leade is waaaaaay looooooong from lots of shooting I guess.

My fa-vo-rite 7mm slug is the RCBS 7mm-168, which is a long bore rider. In a couple other rifles I have it's a superb shooter up to 2400 fps! In the M95 it'll do okay up to about 1400 fps. I think that the short drive band engraving surface MAY be slidding a bit or maybe even there is a bit of bullet tipping going on in it's long unsupported trip from the case.

So how do you mitigate the long distance? You move the full body diameter of the slug out closer. That's impossible with the RCBS slug as it'd be out of the caseneck so you switch bullet designs to a Loverin. That's what I used in the Chilean, the Lyman 150gr Loverin. With that slug I get pretty decent results up to about 1800 fps. You can also:

1) Cast your slugs hard
2) Shoot them big as the throat allows, as in 'as cast'
3) Use a slower powder that is a bit slower in accelerating the slug along
4) Seat your slug out as far as you can. The limitations being the length of the mag if you want to feed from it.

My 1898 Krag is also somewhat worn, yet it will shoot the 220gr 311284 pretty well. The other slugs I've tried in it could be a bit problematic in duplicating as one, the Ly 311407 which is a 185gr Loverin is NLA. The other is the Bator/Lee custom C311210F which was a custom item and also NLA. Short of finding a heavy Loverin a good design would seem to be that Lyman 30cal number 311644 which mimics the Lyman 150gr 6.5 mm mould (which is ALSO NLA). I think it's supposed to be 195grs, but has a very short bore size nose and a long full diameter body for good support.

Another possibility is to use a slug intended for the "Fat 30's". Usually these will have a nose of .302" or so and may allow you to actually reach out there and touch the lands. The Krags have been known on occasion to run a bit large, so being able to size the body to .310", .311", or maybe even .312" will help center in the throat with the nose touching, or at least very close and STILL feed through the magazine.

............Buckshot



Buckshot2 posted on 02/15/2004 08:27:22

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Stan:

The condition you describe is typical of a Krag barrel that has been fired more than about 1000 rounds with the old service ammunition.  The first generation smokeless powders were heavy on nitroglycerin, were uncoated, and burned at very high temperatures, resulting in rapid (by today's standards) erosion of the throat.  The rate was considered acceptable in the Krag loadings, but the heavier charges in the first M1903 ammunition (30-03) caused barrels to become unserviceable after less than 1000 rounds.  The "quick fix" for 30-03 was to decrease the charge to decrease the muzzle velocity  by 100 fps.  Shortly thereafter, coated double base powders gave more acceptable barrel life with higher velocities of the M1906 ammunition.

My 1898 and 1896 both have throats that are as you described.  My 1898 is otherwise new-looking: the balance of the bore is bright shiny, and sharp.  It is a joy to shoot with the 311284, 311291, 311467, and 311335.  I have found that "hard" bullets are unnecessary, plain wheelweights, untreated, suffice for the loads that I use.  The 1898 long rifle will punch out the X and ten-rings of the MR-51 target at 200 yards with satisfying regularity.  I'm still working with the 1896.

 

Resp'y,

Bob S.

 



Bob_S posted on 02/15/2004 14:35:41

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Reply to : StanDahl


After a pre-shooting cleaning session with my 'new' Krag, I notice that there seems to be considerably shallower rifling near the breech than there was when I started. I guess there was some crud built up on the lands and now it's gone. It looks like for about the first 2" of bore the lands aren't much more than speed bumps, then they get a little sharper down the line. My concern is the effect that this will have on the bullet as it goes down the bore. Will this cause some stripping to occur before engraving, thus allowing wider grooves to be cut on the bullet and gas cutting to happen? If so, is there anything I can do in loading/casting to reduce this possibility? Will this have a big effect on accuracy? Thanks, Stan

 

Stan what most BR cast shooters do in essense is cut a throating like yours. These tapered throats go from 1.5-1 degree per side down to the lowest I've observed is 30 minutes. Now that's a shallow angle.. Gas cutting isn't in play IF the bullet is throat dia at it's forward edge and is being swaged down into that throat by a larger driving section. But if the bullet is seated into or very near the land origin the lube should provide enough seal to forgo cutting. Then depending on alloy hardeness, powder speed and psi's you have obturation to bump the bullet.

My 03 has a similar throating being made 98 yrs ago and shooten's cast fine. I'd imagine mine acquired the same kind of throat as your Krag via yrs of use with older ammo. And looked similarily crude laden starting out. Shooten's fine now and never leads either.



I am Aladin posted on 02/15/2004 16:05:54

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Ah yes the cleaning!  Krags can contain alot of crud. As previously mentioned an erroded throat is not necessarily the kiss of death for cast bullets. As long as the bullet body is the size of the largest part of the worn throat, or a little larger..and...the nose is supported by the top of the lands you will be OK.  If you are into making a chamber and throat cast that will give you a world of information. If not you can do it by the trial and error.

Krags have generous chamber necks and throats and so you can use cast bullet up to .312 without any problems. go larger than that and you will probably have to turn the necks of your case to thin them. By turning the case necks you could use bullets up to .314 and that should be big enough to take care of any wear in the first couple of inches of the barrel. I would start with the biggest sizing diameter that will chamber without force.

Moulds with noses larger than .299-.300 are not all that common. I have a Lyman 311291 that goes .302 on the nose and a SAECO .303 British that runs .304. Either of those might work depending on how much wear there is on the lands.

I would also think of a Loverin style mould like 311467. With it's sucessive smaller nose bands, it would give a good fit if the body is the right size for the worn grooves. I have two of those moulds my 311467U casts .309 and my regular 311467 casts .312

Of course you can always "Beagle" just about any mould to increase the nose and/or body size.

Don't be disappointed in your Krag...I think it can be made to shoot cast just fine, but bullet fit will be inportant. Bullet fit is important in all cast bullet shooting, but in your case it becomes even more critical. have fun!!!



Chargar posted on 02/15/2004 18:29:45

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I AM Aladin--"These tapered throats go from 1.5-1 degrees per side down to the lowest one I observed 30 minutes". Hell.I looked at one for only 5 minutes once.

CarpetmanRay posted on 02/15/2004 20:43:52

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