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For those of you who think the Krag has a weak action...

Discussion in 'Rifle Country' started by .455_Hunter, Nov 11, 2009.

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  1. .455_Hunter

    .455_Hunter Member

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  2. saturno_v

    saturno_v Member

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    I don't know much about the Krag action but the 405 Winchester is a low pressure round (I believe around 30,000 PSI SAAMI specs).
    The 30-40 Krag should be higher pressure.

    Yes the 405 Win is powerful but low pressure nevertheless.
     
  3. natman

    natman Member

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    The 405 Winchester is in the same ballpark as the 30-40 Krag in pressure, so drawing conclusions about the strength of the action because one guy converted one and it isn't in splinters yet is a bit of a stretch.
     
  4. saturno_v

    saturno_v Member

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    natman

    Actually I think the 30-40 Krag is a bit higher pressure than a 405 WCF...
     
  5. Slamfire

    Slamfire Member

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    Pre 1900 metallurgy is primitive beyond belief. They barely understood phase changes, phase diagrams, transition temperatures, you name it. Pre 1920 metallurgy was inexact science and it is not till you get into the 30’s does metal science become a mature science.

    Just saw a show on the Titanic. They made a big point on how much slag was in the wrough iron rivets. That was 1912.

    US Krag’s were all built around 1898. The plain carbon steels used then are now considered suitable for rebar. These rifles have been known to crack the single locking lug with 30-40 Krag ammo. I saw one cracked lug at the range. A 30-40 Krag will push a 220 bullet 2200 fps. That is pretty mild in today’s world.

    This guy increased the bore diameter which should make a difference in total load, or maybe total impulse on the bolt.

    I would not buy the rifle even though the workmanship looks decent. I think it is an accident waiting to happen.

    This might be a feasible conversion if he had used a Norwegian krag from the 30’s.
     
  6. Avenger29

    Avenger29 Member

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    And remember folks, just because somebody came up with a harebrained idea and made it, does not automatically make it a good idea to try it out for yourself, nor does it prove anything.
     
  7. Kernel

    Kernel Member

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    SAAMI spec on the .405 WCF is 44,000 psi. Pressurewise, that puts it between the .30-30 (42k) and the .300 Savage (47k).
     
  8. Art Eatman

    Art Eatman Administrator Staff Member

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    The rule of thumb for any single-lug bolt-gun or a rear-locking action like the Winchester Model 94 is about 40,000 psi. At or below that you might get cracking, but it's not gonna come all apart at the seams...
     
  9. Gordon

    Gordon Member

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    FWIW Col. Cooper had more 30-40 Krag ammo stashed in his bunker the last couple years before his demise than any other caliber. He a nice Krag sporter with ghostring that he could use quite well! His "rough rifle" of choice. I have one too, for the heck of it.Sure is slick and handy and reliable on anything in the Americas though......
     
  10. Jim K

    Jim K Member

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    Well, the strength of an action does not depend on how many rifles or ammunition of that type someone had stashed away.

    The .405 is a higher pressure round than the .30-40 as well as having a slightly larger internal base diameter. The base size is critical, because it determines the amount of actual pressure pressing on the breech face. Pressure per square inch is good enough for comparison, but when determining the suitability of a given action, the critical figure is the absolute pressure at the breech face.

    Jim
     
  11. RonE

    RonE Member

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    That is a great looking rifle. It has been modified to feed the modified .405 cartridges which doesn't appeal to me. I also notice that it looks like a $1,500 rifle but no one seems to be in the market of such a combination of oddities. I notice no bids. It was quite and artist that built that gun.
     
  12. jim in Anchorage

    jim in Anchorage Member

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    I wonder how much bolt face pressure that straight wall .405 really has. In my handbook for shooters & reloaders volume 1 by Ackley. he rechambered a94 Winchester to a improved 30-30 with minimum case taper. The locking lug was removed leaving only the finger lever to support the bolt. It was then fired several times with 40,000 psi loads, with no damage to gun or brass. Apparently the straight wall case clings tightly enough to the chamber that back trust is non existent, at least to a psi level that would separate the solid base.
     
  13. Maverick223

    Maverick223 Member

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    Very true, that is the only aspect that actually regards the action and not the bbl. The bolt thrust would be significantly higher in the .405Win., and for that reason I wouldn't feel comfortable with the rifle (not knowing if it is truly safe).

    That is incredibly dangerous, and if it really was tried I am surprised that someone was not hurt or killed in the process.
    There is no way that friction can support that kind of pressure (straight walled or not), it is thousands of pounds of force pushing back, you must contain the entire cartridge (save for the obvious...the projectile) in a very stout pressure vessel, this must include the rear of the cartridge.

    :)
     
  14. jim in Anchorage

    jim in Anchorage Member

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    I think P.O Ackley would know how to conduct a gun test safely. You DO know who he is, right?
    No need to belive me. Get P.O. Ackley's hand book for shooters and reloaders,volume 1, copyright 1962, by publishers press. Chapter on pressure. pages 137-149.
     
  15. R.W.Dale

    R.W.Dale Member

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    You guys need to look at this mans work for what it is. A work on internal ballistics and rife smithing based on what was known a half century ago. Much of his work particularly as it relates to internal ballistics has time and time again been proven to be completely erroneous and based on the same false assumptions everyone used 50 or 60yrs ago. Particularly his pressure sign masking AI'ing of cartridges.

    Two words. STRAIGHT BLOWBACK

    try to hold the bolt closed after firing a 9mm or 45acp carbine. After you get your thumb sewn back on you'll realize that just cause someone wrote a book and gets their name mentioned in magazines doesn't make their entire work correct
     
  16. Maverick223

    Maverick223 Member

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    If the above account was correct, apparently he did not. Never met...but I know of him very well...Your point? Do you think he was a faultless god...superhuman in all of his endeavors? I can't help but notice that none of his cartridges have gained mainstream success...I suppose everyone else just doesn't realize his genius. I am not saying that he didn't make some improvements or that all of his work was flawed...but he made mistakes just like everyone else.

    Is this where he states that "a rifle needs no containment at the base of the cartridge due to case friction"? I don't think that anyone with any general knowledge of firearms mechanics, pressure vessels, fluid dynamics, or any form of basic physics would be stupid enough to make that claim.

    Exactly, and that is with a low pressure, low bolt thrust pistol cartridge. A rifle cartridge is MUCH more severe. If a rifle (firing a full power rifle cartridge) used a blowback mechanism like a pistol, the weight of the slide or bolt would be astronomical (over 100lbs for some rifles).

    :)
     
  17. jim in Anchorage

    jim in Anchorage Member

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    I never defended every thing the man wrote. But the fact remains he DID remove the bolt from a 94, he DID fire it with a straight case 30-30 developing 40,000 psi, and the gun and case DID survive. In fact the only abnormality noted was the primer protruded somewhat-which makes perfect sense-the firing pin shoved the case forward, the pressure locked it in place and the primer backed into the available headspace

    This was not theory, guesswork or speculation. It was a actual experiment carried out on a real gun.

    No I would not try to hold a 9mm or .45 in the chamber for the simple reason it dosn't GENERATE ENOUGH PRESSURE TO LOCK THE CASE. Have you not noticed blow backs are confined to low pressure cartages?
     
  18. R.W.Dale

    R.W.Dale Member

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    9mm Luger +P 38,500psi
    40 S&W 35,000psi
    according to your theory then the margin for saftey is only 1500psi of course this assumes PO Ackley had any idea what the pressures involved in the test were beyond pretty much guessing

    Really then why are the Handi rifle folks stretching the piss out of frames frames when they shoot a bunch of warm 500magnum loads?

    Bolt thrust is an easily calculated variable that always increases as pressure does. The brass itself WILL not contain pressure at the case head if unsupported
     
  19. jim in Anchorage

    jim in Anchorage Member

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    This seems to be controversial. Before anyone else replays let me make two things clear;

    #1 it only applies to straight wall,clean cases. No oil can be present in the chamber or on the case.
    #2 It only applies till pressures exceed the yield point of the brass; commonly accepted at approximately 40,000 psi even by us modern, enlightened folk.
     
  20. jim in Anchorage

    jim in Anchorage Member

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    I am not a pistol guy but I am not aware of any straight blowback design meant for 38,500 psi loads.

    Factory loads.
     
    Last edited: Nov 12, 2009
  21. R.W.Dale

    R.W.Dale Member

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    Just about any 9mm carbine other than the marlin is going to be a straight blowback operated arm that'll digest 9mm+p without a hiccup

    factory loads? What cartridge? A straight walled 30/30 50years ago was a 38/55 a cartridge loaded to much lower pressures than 40,000psi. Either way you really really contradict your own theory with the statment that 35,000 to 38,500psi isn't enough pressure but 40k+ is too much

    plus a m94 with the bolt cut off isn't exactly unlocked. The hand lever and the hammer are both at a state of conciderable of mechanical advantage resisting the bolts ability to be pushed rearward.

    Of course none of this has any bearing whatsoever on the safety of a Krag in 405
     
  22. Maverick223

    Maverick223 Member

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    My point exactly.

    I take it that you are not aware of the .357Sig cartridge then. It has a (non +P) SAAMI specified maximum pressure of 40,000psi, so I am sure that some factory defense loads exceed 38.5kpsi.

    The only thing that might keep one from having the bolt come undone during firing.

    :)
     
  23. jim in Anchorage

    jim in Anchorage Member

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    Examples?
    A factory 30-30 with the normal case taper. As you know, the 30-30 headspaces on the rim. When fired the case walls conform to the straight chamber
    Wrong. The action only contains the back thrust; The barrel contains the pressure of the body of the cartridge.
     
  24. R.W.Dale

    R.W.Dale Member

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    Examples?

    Ruger pc9 & 40
    keltec sub 2k
    high point 995
    beretta storm
    9mm ar15's
    and just about any other 9mm carbine you can think of
    sounds like you're describing a fireform load with a grossly undersized bullet IE no pressure
     
  25. Jim K

    Jim K Member

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    When a round is fired, the case expands and the pressure pushes it against the chamber wall. But unless the case is made of some material that cannot stretch ("unobtanium"), the base of the case will be pushed back by the same pressure, stretching the case. If headspace allows, the case will stretch far enough to break. While this is rarely dangerous to the shooter, it will tie up the rifle, which is why the military puts much more emphasis on checking headspace than most civilians. In civilian life, an inoperable rifle rarely results in the death of its user.

    So, no, when high pressures are involved, the case clinging to the chamber wall will not reduce pressure on the breech face "tightly enough ... that back trust is non existent".

    For a case like the 7.62 NATO, the absolute pressure on the breech face is roughly 5000 pounds, and it is applied suddenly in a blow, not a gentle push. For an idea what that means, imagine a rifle with its butt on the ground and barrel pointing upward, with a steel rod down the barrel. On the rod is a platform onto which a Ford F150 Crew Cab pickup truck is dropped from a crane. Of course, such a thing could only be imagined, but it serves to give an idea of the kind of pressure involved in an ordinary rifle.

    Jim
     
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