Maximum Safe Radial Expansion for Brass Cased Rifle Cartridges

[jmoore]

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.

[Edward Horton]

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.

Mr. jmoore

YOU decided to bring the radial expansion topic from the Enfield forum to this forum and mentioned ME by name specifically. You also decided to be the funny comic in the Enfield forum with your out of place comments.

I'm now the head comic here and I'm returning the favor, also talking about radial expansion in the Enfield Rifle is just like measuring the length of used bolt heads in relation to the number stamped on the bolt head, it doesn't prove anything.

Discussing radial cartridge expansion doesn't prove anything either because of the wide variations in Enfield chamber diameters and extreme variations in .303 cartridge manufacturing.

Therefore Mr. jmoore it proves even LESS talking about radial expansion of SAAMI commercially made .303 cartridge cases when these cases were NEVER designed to to be shot in a military chamber.

The Enfield rifle has two types of chambers, good ol' biggins and big ol' gooduns' and our skinny poorly made American .303 cartridge cases are built like an old bias ply tire in a radial filled world.

In closing Mr. jmoore I have learned all I want to know about American made .303 cases that stretch radially and axially and fall apart. I'm looking for .303 cases made of Kryptonite and I think the Prvi Partizan .303 cases fill that need.



The shame of it is some people actually grease their cartridges to stop case stretching but this doubles the bolt thrust and damages their rifles in the process.



Mr. jmoore, someday we will have to "do lunch", and I'm very good at serving crow.

[jmoore]

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....

[Edward Horton]

Mr. jmoore

If I wanted to shoot .303 ammunition out of a mosin I would join the Communist Party.

You did not read what I said in my postings about checking and measuring 500 once fired Greek HXP cases for case stretching. Each case was checked at three different locations in the web area, which was very time consuming and NO case stretching was found on any of the 500 HXP cases.

I bought these once fired cases from Brian Dick and these cases had been fired in Vickers machine guns, Bren machine guns and various Enfield Rifles and these cases had no thinning or stretching.

My point being that after testing three different lot numbers of unfired Winchester cases and two different boxes of factory Winchester .303 ammunition the Winchester cases all stretched and thinned.

It's the quality of the brass and how the cases are made today that makes the difference and my two rear locking Remington 788s didn't eat brass and my 30-30 Winchester doesn't eat brass with it's rear locking lugs either.

Commercial American .303 ammunition is only loaded to approximately 43,000 CUP and it still stretches and thins, and the Greek HXP military ammunition is loaded much hotter and these cases did not stretch.

So you just keep your commie pinko pervert mosin out of the Enfield forum comrade or you will be sent to a Siberian Gulag.

If you want to do some serious testing then pick one enfield and test fire different make cases at different pressures at different head space settings and report your findings.

[ireload2]

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.

[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.

[Edward Horton]

How many single shot disposable battle rifles do you know of that the cases fail immediately when fired.

[jmoore]

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.

[Edward Horton]

Mr. jmoore

The bolt pictured below is resting on a .064 head space gauge, this means I have the head space set on this Enfield .003 over my Winchester case rim thickness or between .061-.062 and this is under the minimum head space standard.





The commercial factory loaded Winchester ammunition fired in this Enfield stretched and thinned .001 average in the web area. With the original bolt head and the head space set at .067 these some Winchesters cases stretched .009 in the web area on first firing.



With a rubber o-ring installed around the case and a #0 bolt head lapped to over .084 head space the same Winchester cases had “ZERO” stretching in the web area.

Please notice I didn’t need a Mosin to get these results and this thread started in the Enfield forum. Lets NOT mix apples and oranges, this thread is getting a little too fruity with the addition any non-Enfield rifles.


The .303 case below has suffered from excess radial expansion at the speed of light and collapsed into a Black hole sucking the surrounding shooters into an alternate universe.



Rumor has it this .303 cartridge was fired in a converted Mosin by so called galactic "experts".

[Parashooter]

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.