Hi my friend Franta has sent me a photo of 7,92x57 SMKH cut . What is interesting why is the core crashed. Can it somebody explain. Thx.
Maybe it wasn’t an SMKH but a phosphorus projectile that burned out?
The Pmk patrone had also an armor piercing core even if it as not the same design than a smkH
Correct, not a PmK. Something incendiary(phosphorus) is what I said.
It’s too short to really be anything regular?
Bullet length 28.55 mm would be correct for SmK(H), the internal layout (lead core in the tip), too. Someone knowledgeable in sintered tungsten carbide manufacture and properties is needed in my view.
My bad. I thought the SMKH was of the longer, boattail type. Thanks for the education.
It still looks like the core was replaced by something or a burned out incendiary mix. Maybe manufacturing sabotage by forced labor?
The cores, internally called “Bohrspitzen” were ordered by the Waffenamt.
The two major factories were the companies; Krupp and Röchling Buderus, Plant Finowfurt.
This means the cores became in ownership of HWA. The cores were shipped from Abnahmestelle Eberswalde, for Röchling Boderus cores, to the Abnahmestelle from Polte.
They checked them and Polte loaded them. After the testing (Beschuss) for example by Wa Prüf 1/IIb the cartridges were shipped back to HWA. Polte get paid for preparing the bullet and loading the cartridge.
I don’t know if I read the head stamp correctly.
This is P S* 13 39.
This head stamp is, until now, not known from a cartridge with a SmK-H bullet.
By all the checking and controlling it is a mystery to me the way the bullet looks inside.
I don’t think it came out of the plant this way.
Which method are done for section the bullet?
Perhaps just a manufacturing error of the tungsten core. -Ger
Sorry, no, a manufacturing error is no plausible explanation in my view.
As Dutch already explained, core manufacture was done at highly specialized factories that delivered the cores to the bullet manufacturers. Archive records show that the completed cores had relatively large tolerances and were required to be sorted by weight. That means every single core had to be checked and sorted in the factory and was re-checked at the bullet manufacturing plant. I see no realistic chance for a manufacturing error of the dimension shown in the photo getting through.
These cores were absolutely high-tech at the time, not an ordinary mass-produced item.
Sabotage by coerced labourers as mentioned in an earlier message is possible (at the bullet making plant) and is known to have happened with other items. But considering that SmK(H) was only made very early in the war because tungsten was to be saved for larger calibers, I consider this also as not probable. Germany ran its economy on a peacetime footing early in the war, the crime of using coerced labour was commited mostly later, from 1942/43 onwards.
It would be interesting to see a second 1939 dated SmKH specimen sectioned to see how it compares. Yes, I do realize that these are quite scarce. -Ger
@JPeelen So it’s the wrong projectile for the case? Have a guess as to what it is?
This looks like a classic brittle fracture, probably caused during the process to join a (possibly) defective core with the jacket. The light gray areas between the polished surfaces look like textbook brittle fracture surfaces. It looks like some pieces fell out when the projectile was sectioned.
If the core was unusually brittle or had large residual stresses built up, it would look normal to the naked eye (and also to any non-destructive inspection method existing at that time). However, it would not take too much stress when putting the jacket over the core to cause a catastrophic failure (some metals can even spontaneously “explode” due to high residual stresses building up due to heat, etc.).
Whether the core is tungsten carbide, tungsten alloy or hardened steel, any of these can be extremely brittle if the manufacturing and heat treating process weren’t quite right during core manufacturing. They may appear normal until external stress or somewhat elevated temperature initiates the failure. Another possibility is a normal core (but still somewhat brittle as is the nature of AP cores) that was simply overstressed during assembly to the jacket (crushed with too much force).
I do not have the slightest idea what created the core structure in franta’s photo. As I wrote in an earlier message, we need someone experienced in the sintered tungsten carbide field.
I looked at it again and you guys are right. I thought the whole time it was an ash matrix from something burning up… It’s definitely a fractured solid and the “crashed” description of it makes a lot more sense.
I’ve done failure analysis of many brittle fractures under an electron microscope and the photo above is a good representation of one (regardless of the material or method of viewing it). Photos can be deceiving, but there is little doubt that this is simply a brittle fracture caused by tensile stress overload. How exactly the overload took place is open to some conjecture.
One other possibility for the failure is it may have been caused by sectioning the projectile. If too much heat built up during sectioning or grinding, it could also cause the fracture. Excessive heat or force both have the end result of causing too much stress.
Larry, when it got so hot the TC core got affected shouldn’t the lead sleeve be molten?
Alex, you are right about the lead. I need to pay more attention to all of the components. So it seems more likely to have been overstressed (crushed) when it was assembled into the jacket. Plus, whoever sectioned it must have known something because very few abrasives are hard enough to cut TC.
When I first looked at the photo, it appeared to be like a sponge. But looking more closely I could see what looks like the TC core material ground or polished showing up as dark “islands” (it looks like there may be some scratches on the polished core toward the base). It is very easy to see more than one thing when looking at this image (at least for me).
Zdravím přátelé, řezi 7,92 x 57 dělám pro svou sbírku (tablo) na této magnetické brusce.
Střela S.m.K. (H) byla opravdu velmi tvrdá. Střela byla mnou vyjmuta z náboje 7,92x57 P S* 13 39
Polte Werke. Pulver (prách) NP. Gew. RP. 1,8 x 1,3/0,2.
Hello friends, řezi 7, 92 x 57 fastened my collection () on this magnetic grinder. The S. M.K. (H) was very hard. The shot was me has been removed from our fight 7, P S * 13 39 92x57 Polte Werke. Pulver (prách) NP. Gew. RP. 1, 3, 8 x 1 / 0, 2.![M%20bruska|690x920]