30-40 krag reloading

Discussion in 'The Ammo & Reloading Forum' started by GMFWoodchuck, Oct 26, 2008.

  1. GMFWoodchuck

    GMFWoodchuck New Member

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    I have done some reading on the 30-40 krags. Supposedly the bore diameters runall over the map. .308 all the way to .314. From what I have read (I forget the book, I was browsing in the store, speer maybe.) they suggested to check the bore diameter and to use the .310 bullets (for the
    .303 brittish) and to size the cases as such. I am probably going to buy my reloading stuff sometime after cristmas and I (currently) planning on the rcbs rock chucker supreme master kit. Assuming that my dad's krag is the "wrong" diameter what else would I need to get to recitfy this situation. It would seem to me that the 30-40 dies would be for the wrong diameter.
    I will check the diameter before buying anything, but I just wanted to know what kind of budget I am dealing with.

    Thanks alot.
  2. GMFWoodchuck

    GMFWoodchuck New Member

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    What I have read confuses me a little bit, that's why I am asking.
  3. Bindernut

    Bindernut Well-Known Member

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    You'll need to slug the bore of the rifle in question to get a positive measurement of it's bore diameter. If it's oversize, you can substitute a larger expander ball for the .308 diameter one on the decapping stem to closer match the bullets that you'll be using. If you're going to wind up using .310 bullets, then get a spare expander ball in .310 diameter and swap it with the original one. Be sure to note this change on the dies for future reference.

    You won't need completely different dies...the expander ball is the final step of the resizing die and the neck will be sized to it's diameter on the press ram downstroke.
    Last edited: Oct 26, 2008
  4. GMFWoodchuck

    GMFWoodchuck New Member

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    I see. How do I slug the bore?
  5. Bindernut

    Bindernut Well-Known Member

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    You'll need a soft lead slug. An unsized cast lead bullet or pretty much anything lightly larger than the bore will do...just make sure it's pure lead and not a hard-lead alloy. You could use a #0 or #00 buckshot BB as the slug for your Krag (.32" and .34" respectively).

    Drive the slug through the bore using a wooden dowel. Do NOT use a metal cleaning rod to drive it through the bore you can damage the rifling very easily!!!
    I use a very light machine/penetrating oil as lubricant when slugging a barrel...PB Blaster, JB80 or WD40 will work. Once you've driven the slug through the bore, it will be swaged down into the rifling and you can measure the diameter of the slug afterwards to determine the bore diameter. You probably won't be able to get a very accurate measurement down to ten thousands of an inch with a caliper...would be best to use a micrometer if you can borrow one.
    Here's an article by Mike Venturino that describes the process even better.
    http://findarticles.com/p/articles/mi_m0BQY/is_2_54/ai_n21175826
  6. Bindernut

    Bindernut Well-Known Member

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    I should also add that I'd bet that you'll probably wind up just using .308 diameter bullets but this will give you a better idea if the bore is horribly oversize, which can cause groups to be really erratic.

    Also keep in mind that the Krags are old rifles and if you do wind up using a larger diameter bullet that this might affect chamber pressures so be sure to keep the loads in the light end of the data you're using if the data was worked up using .308 diameter bullets. Don't try to "hot-rod" it, but by all means enjoy shooting it!
  7. GMFWoodchuck

    GMFWoodchuck New Member

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    Okay. Thanks for the info! I was imagining pour hot lead and I was like no way dude. But that makes sense. On a side note though, some calipers can measure inside diameters would that be sufficient? I am probably going to slug it anyway just in case.
  8. Bindernut

    Bindernut Well-Known Member

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    You probably could use an inside-measuring device to get the diameter at the muzzle. This will only get ya the diameter up front though.

    In theory, the bore should be the same diameter all the way through, but if it's an old rifle it might be eroded more at the muzzle (from many years of cleaning rods or even dust/bullet erosion...you get more dust in your barrel at the muzzle and it'll slowly lap away the bore with each shot).
    Slugging would be the best option. This will ensure that you measure the smallest bore diameter in the entire barrel.
  9. GMFWoodchuck

    GMFWoodchuck New Member

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    Ahh...That does make sense.
  10. LDBennett

    LDBennett Well-Known Member

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    I would add that the barrel dimension you are after is the grove diameter, not the bore diameter.

    The cast bullets have to be a few thousandths larger (how many I don't know as I don't cast bullets???) than the diameter of the grooves, not the bore. It depends on how many grooves there are (odd or even number) as to whether you can even measure the groove diameter with any instrument from just measuring the barrel muzzle without slugging it.

    I do shoot 30-40 Krag ammo in a Winchester replica 1895 imported by Browning from Japan and it indeed takes 308 bullets because it is a modern firearm regardless that it looks like a Winchester 1895.

    LDBennnett
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