7.92 x57 pressure cartridge


#1

In the book German 7,9 military ammunition of D.Kent is on page 132 a drawing of a pressure cartridge. Does anyone more information or a life round of this ammunition? I have one empty case in my collection but I will come back later with a picture.

451kr.


#2

This is a so called Messpatrone.

Drilled a hole and on the side they put a piece of copper in a measure barrel were the hole is.
Later they measured the size of the copper. With a formula they calculate the pressure inside the case. (piezo)

Now the ammo factory


#3

Dutch–You have the two types of pressure testing mixed up. The Piezo type is the current electric method. The older type used copper crushers to measure the pressure in CUP (Copper Units of Pressure).


#4

Ron, Thank you.

Did not know how the name of the copper method

Dutch


#5

I have two of these rounds in my own collection. One I know is correct; the other I cannot vouch for its authenticity. Both are NPE cases - no powder or bullet. I suspect that these rounds may have actually been handloded at whatever facilities were testing the pressures, in the developments of loads using different lots of powder (although the German 7.9 load for at least ball ammunition was pretty uniform throughout production). They are both for the copper-crush method of pressure determination.

My first round is a lacquered-steel case, headstamped “cg St+ 4 ?.” there is a question mark at the year, as it cannot be read. These rounds have a slot cut in the head (rim) of the cartridge exactly opposite to the hole in the case, so that they may be positioned correctly in the test fixture. the primer is the standard steel-cupped Zdh. 30-40. There are no primer crimps nor primer seal, two things pointing to the authenticity of this round. The holw is covered with a piece of fabric, a rust-brown in color.

The second round is a brass case, headstamped “aux S* 36 4?” (the second digit of the year-date cannot be read due to the positioning slot cut in the rim), with Zdh. 30/40, but with primer stakes and a blue seal. There is an uncovered 9mm (.349-356") hole in the side of the case, about 4,5mm above the extractor-groove bevel. The primer crimps and colored seal make me question the authenticity of this round, but not enough to destroy it. Admiitedly, based on the other “cg” case, the hole in the side of the case is positioned properly.


#6

Picture or maybe a drawing on how it works and what it looked like, too interesting to just let it go with as description. Thanks Vic


#7

Vic - later, when I have a little more time, I will look through my fiels and see if I can find an easily reproduced picture of a copper crush test fixture, or even a gun so equipped. I am not artistically capable of drawing one, even though I have a pretty good idea of what the text fixtures looked like, as well as the alter rifles (and even a Nambu pistol) to be used as a pressure-test gun only. If I find anything, I will also post a scan of my two cartridges.

In the interim, if anyone beats me to it, I will be very happy.


#8

This is a bit tangential, but in Phil Sharpe’s Complete guide to handloading (1937, and probably later eds.) there is a picture of a tin of the small copper cylinders, the ones pictured being of French manufacture. A very interesting and, I assume, rather rare item. JG


#9

I have a photo or two of the old Frankford Arsenal pressure guns but they are not very good quality. If John can’t find anything in his files I’ll try and doctor one to show here.

It is important to note that the two methods Dutch outlined do not result in the same readings for any particular cartridge and there is no formula or chart for converting one to the other. The Piezo method does measure actual psi whereas the copper crusher method only measures copper units of pressure. They are not the same thing. The numbers can be close or very much different depending on a lot of factors such as how high the pressure is, the alloy of the copper pellets, the skill of the operator, etc.

Ray


#10

Here is some information on CUP from the SAAMI manual.I have some of the actual copper crushers someplace. If I can find them I wil post a scan.




#11

Here is a related URL:

ttp://www.reloadbench.com/gloss/cuppsi.html

Here is a quote from another Forum:

There are three Piezo methods, the copper crusher method and the strain gauge method. Of the three, the strain gauge method actually produces the lowest (best) sigma-E, a statistical projection of how likely results are to be accurate, and is the only one most amateurs can hope to afford. There were earlier problems with this method, partly to do with speed of analog elements of the measuring system and partly due to analog to digital pre-conversion filtering, but it has been improved upon since. The Piezo method, which had been presumed in the past to have best accuracy, has turned out to have some issues of its own.

Copper crusher and both SAMMI and CIP piezo transducers work by pressure applied to a piston through a hole in the side of the chamber. The SAMMI copper crusher and piezo transducers typically have the piston located in the side of the chamber 1


#12

John,

I seen already some of these 7.92 pressure cartridges in steel case by other collectors but no brass cases.
Recently I got a 7.92 aluminium pressure case in my collection. Is there any information about test with alu cases.

451kr


#13

Here is a SAAMI Size “B” copper crusher. The diminisions are 0.225 x 0.500 inches.


#14

I don’t have any information on the aluminum case tests concerning those cartridges with the headstamp “T” at 12 O’Clock and various letters at 6 O’Clock, like you show. I have not seen the pressure test rounds in these, although I have five or six pieces from the series. Most of mine are in pretty wretched condition. I could not afford the really nice specimens that turned up.

You have a great specimen. The hole in yours, and the slot, are virtually identical in size and placement to those on my own rounds. Makes me think that maybe my brass-cased one is legitimate after all.

Thanks for posting that. I needn’t post pictures of my rounds now - they appear, in anything that matters to this thread, exactly as yours, and you do a better job than I with pictures.


#15

Phil Sharpe’s Complete guide to handloading 1937 can be found at :
stevespages.com/zip/complete_gui … 201937.zip

Glenn


#16

451kr

Do my eyes decieve me?? Does that aluminum test case have a flashole??

Ray


#17
  1. I have seen a lot of French ctges with a crusher hole but all had a lot smaller hole (about 2 mm) was the one shown on your picture.

CIP pressure test with crushers must be different from Saami ones I think.

  1. Regarding the WWII 7.92 crusher ctges I have seen they had a small (2 mm) hole (they were with plastic body and brass base).

JP


#18

Ray,

Yes, the case has a flashole.
The case was found years ago in the ground I think oxidise of the aluminium closed the flashole.

451kr.


#19

Jean Pierre - while I am not especially scientifically-minded, and do not know the ins and outs of the copper-crush system (I do understand the basic principle, of course), I do not know why they vary, but the truth is, the holes on all copper-crush test cartridges are not the same, nor are they all located in the same position. As you stated, the French 9mm ones I have have a very small hole, but I have noted that they are found at different heights n the cases. I have three Swedish ones in 9mm, and they have holes of approximately 4.90mm - 4.95mm (they are very hard to measure, and are all located at the same height on the case as each other. The copper pellet for them, one of which I have, measures precisely 9.00mm in diameter and precisely 12.00mm in length.

Ray - I noticed the lack of a flash hole in the aluminum copper-crush round pictured as well. Doesn’t make any sense, does it? I don’t know what these tests were all about. I have six pieces from them in my own collection, all damaged in one way or another. (They were found in a dump in Eastern Germany, I hear, and time has ravaged them, although some of the damage appears to be not related to deterioration while in the ground. It appears that the tests were as much a test of primers and priming systems as of aluminum cases. I have the following:

TJ - Primer intact, but corroded to a point of not knowing material of cup, except that it is not steel. No visible flash hole inside the case.

TL - Primer intact, copper cup, 2 Berdan-type flash holes.

TL - No primer at all. Single, centered Boxer-type flash hole.

TM - No primer cup but a ring of copper proving without doubt that a copper primer cup has rotted out. No visible flash holes.

TM - Primer intact, copper primer cup, single, off-center Berdan-type flash hole.

TN - Primer intact, brass primer cup, 2 Berdan-type flash holes.

It would be interesting to know if those with a primer but no flash holes ever had priming compound in them, and if the Berdan types have an anvil built into the flash hole. It would also be interesting to know if the ones with no visibile flash hole have a thin center at the pocket for some sort of primer burn-through test. It would take a much bigger collection of them than I have to find these things out, and a willingness on someone’s part to section a few of these. With the small number in my own collection, despite their condition, I don’t want to chance destroying any of them tampering in any way with them. I understand that over twenty variations were found.

Perhaps someone with much more knowledge than I can fill us in on some of the reasons for the tests, what the headstamps mean (I have been told that a logical explanation of the “T” is for “Troisdorf,” but I don’t know what that interpretation is based on, and why some “primed” cases do not seem to have any flash holes, especially a pressure-test round that in its other features, looks completely legitimate.

Edited for content - some measurements were wrong or incomplete regarding the Swedish 9mm Pressure-test rounds.


#20

I missed 451kr’s reply that his aluminum pressure-test case does have a flash hole. I can see in the picture a small indentation. However, I am not knowledgeable enough to know if aluminum oxidation could so uniformily completely close the flash hole.

Seeing his answer prompted a re-examination of my round headstamped “TJ”. It has an intact primer cup, so examination from the outside was not practical. Instead, I used a .042" wire probe to try to find a flash hole internally, and I was successful in finding the same kind of indentation that appears on the outside in the flash hole of 451kr’s case. After using the end of the wire probe as a scraper, it was deep enough to firmly catch the probe and keep it from moving side to side, but it does not go all the way through, and is much solider than I would anticipate aluminum oxide to be. Again, I know little about thise things - I am not drawing any conclusion, but simply making a layman’s observation with the hope of soliciting a more scientific response. It seems to me, though, that this indentation is NOT drilled completely through. The scraping did yield some aluminum oxide dust when I tapped the mouth of the case on my work bench, but after the initial tiny amount, further scrapping yielded no residue, leading me to believe it was solid aluminum at that point. Again, this may be a totally wrong conclusion. this type of cartridge examination is new to me, even after 45 years of collecting and more of shooting ammunition.