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Knot hole won't develop enough pressure as there's no way to control the powder burn one the bullet leaves the barrel.
Evidently, you aren't really concerned about this aspect of cartridge dynamics. Go back to your headspace dungeon and contemplate your sins.
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02-27-2010 03:42 PM
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Last edited by Edward Horton; 02-27-2010 at 06:16 PM.
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Funny? I don't do funny. Very serious I am.
Even went and collected Moisin parts to piece together the test mule. Going to order reloading dies straight away. Hopefully, will do live fire tests w/ Commercial and military brass until the test mule breaks or results can be finalized under the above stated conditions.
May take a few weeks as I'm working too much to shoot right now.
ETA: I believe that you have misconstrued my intentions re. these two threads.
I also think that if those 0.005-0.007" differences in cartridge OD are significant as to brass life, esp. in relation to the LE and No4 actions, then it might do to consider the variables separately.
Due to its rear locking design, even w/ good headspace, the action stretch, although temporary as it obviously springs back after the load is removed, may also induce a case stretching/ lengthening factor to the situation. Using a front locking Moisin action greatly reduces this factor....
Last edited by jmoore; 03-01-2010 at 02:07 AM.
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Successful use of WW .303 brass in a contemporary of the L-E.
However these bolts are front locking, the brass was loaded to a light drag when the bolt is closed and the chamber has very little radial clearance at the junction of the case head and case wall.
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I AM NOT CONCERNED ABOUT HEADSPACE FOR PURPOSES OF THIS EXPERIMENT! (Sorry, to those who understand the difference in failure modes being investigated.)
Do please read the thread title!
I want to see at what level cases fail immediately!
Also, no concern is being given to caliber or weapon except that it applies to, roughly, the most common 6.5 to 8mm class of "battle rifle" cartridges.
Last edited by jmoore; 03-02-2010 at 01:18 AM.
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How many single shot disposable battle rifles do you know of that the cases fail immediately when fired.
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In WWI SMLEs and Ross rifles come to mind, actually! Not single shots nor disposable, which made it rather worse!
Bad brass then, OLD and/or BAD (according to you) today. Actually, Probably all military rifles have suffered case separations for various reasons. Today there's added factors- no annual inspection by qualified personnel, poor quality ammo, both new and surplus, Bubba, etc.
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Advisory Panel
Originally Posted by
jmoore
I AM NOT CONCERNED ABOUT HEADSPACE FOR PURPOSES OF THIS EXPERIMENT! (Sorry, to those who understand the difference in failure modes being investigated.)
Do please read the thread title!
I want to see at what level cases fail immediately!
Also, no concern is being given to caliber or weapon except that it applies to, roughly, the most common 6.5 to 8mm class of "battle rifle" cartridges.
I think you should start this thread over. It's just too cluttered-up with irrelevant replies.
Here are a few of my thoughts on what I perceive to be the intended subject -
First of all, it's very much related to pressure.
Some examples -
Cases 1 and 2 are from the same lot. Number 1 has been fired and reloaded several times with moderate to heavy jacketed loads. Number 2's career ended when I neglected to trim excess length and the bullet was momentarily entrapped at the chamber mouth, running the pressure significantly above normal maximum. Notice the difference in the extent of radial expansion (blue arrow). Number 3 is a once-fired factory load but of a different make with a thinner solid web. Here are the two types sectioned -
This is to illustrate that we can make judgments about pressure by observing the axial progression of radial expansion - but only to compare cases of the same batch, with minimal variation in dimensions and hardness.
Case number 4 was originally a Lake City .30/06, reformed to 7.62 NATO and used until thoroughly battered, then loaded with fairly mild charge behind a cast bullet and fired in a Swiss 1931 carbine. Although the radial expansion amounts to some .035" (diameter), the low pressure ensured that expansion did not progress anywhere near the solid web, leaving the transition region at a very gentle slope with little danger of failure.
With good brass and low pressure, we can get away with lots of expansion. Take a look at the .45/70 re-formed to .41 Swiss on the right -
.45/70 case expands .045" to fit .41 Swiss chamber, but good brass and low pressure ease the hazard that would ordinarily be involved in such a stunt. (Normally, we'd use .348 Win. cases like the three on the left - or 8mm Lebel, also of appropriate base size)
Adding an outside belt can keep this kind of gross expansion away from the web, allowing significantly undersized brass to serve effectively if more appropriate cases are unavailable.
Although I don't have any sectioned samples showing a partially-cracked web resulting from an oversize chamber, one can be found in an old book from Naramore -
I suspect most cases are made of thicker, maybe better, material today than they were in the 1930's.
From my own experiments during over 50 years of handloading for medium military rifles (specifically 6.5 Arisaka through 7.5 Swiss) I've concluded that good cases made after WWII can normally handle .015" radial expansion at pressures in the 40-50,000 c.u.p. range. Examples are 6.5 Arisaka from .220 Swift, 6.5x55 and 7.5 MAS from .30/06, and 7.5 Swiss from 7.5 MAS. A couple of examples -
6.5 Arisaka from .220 Swift on left, Norma 6.5 Jap. center, from .35 Rem. right.
Finally, it appears to me that the expected failure mode from radial expansion is an axial body split, not a the kind of radial separation we see when a cartridge is fired with excess axial play and strong case/chamber adhesion. I've had very few such low-body splits over the years, and it's invariably been with either questionable or overworked brass fired at normal or even minimum radial clearance.
The axial split shown is a .284 Win. formed to 7.5x55. This is a tight fit, with a .500" case in a .501" chamber. Fatigue? Brass defect? I don't know.
.303 British case head separated after 10th use (fired dry, neck-sized, normal pressure loads). Note that the separation occurred at a very different place than the maximum radial expansion. My conclusion is that the two are not closely related, although there is undoubtedly a small correlation resulting from the minor thinning that results from the increase in diameter.
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Thank You to Parashooter For This Useful Post: