EmericD said:

The US TM9-1985-3 from 1953 lists the capability of the SmK(H) as 19 mm of HHA at 91 m for 0° impact angle

Since its HHA, would that mean that the SMKH exceeds the penetration of the 'ADVAP' style exposed tungsten tip projectile tested here, which penetrates 19mm RHA?

https://ndiastorage.blob.core.usgovcloudapi.net/ndia/2012/armaments/Thursday14062tran.pdf

gatnerd said:

Since its HHA, would that mean that the SMKH exceeds the penetration of the 'ADVAP' style exposed tungsten tip projectile tested here, which penetrates 19mm RHA?

Can't answer that.

In the US document, the standard SmK is rated at 12 mm of "hard armor", and the "high velocity SmK" (SmK v ?) is rated at 14.5 mm (at 100 yards).

https://apps.dtic.mil/sti/pdfs/ADA376695.pdf

In the German document, the SmK v is rated at 12 mm (at 100 m) against a 140-150 kg/mm² plate (or 400-410 Brinell hardness), which is the upper bound of the RHA (300-400 Brinell, depending on the plate thickness), but not really "Hard Armor" (as the current meaning).

https://www.lexpev.nl/downloads/handbuchderflugzeugbordwaffenmunition19361945.pdf

All in all, the SmK(H) is a solid performer even by current standards, due to the core size (8.25 g and 22.5 mm long) and the impact velocity, but it's not magic.

The core of the current 7.62 mm DM151 is nearly as large (22 mm long), but the MV is significantly lower.

The exposed tip 7.62 mm AP in GD-OTS paper was able to defeat ~21 mm of RHA at 100 m. The plate hardness was only 300 Brinell, but against WC core the steel hardness does not play a significant role.

EmericD said:

I've also found those wild claims of 20 mm RHA at 500 m for the Smk(H), but they simply don't make sense to me.

I also find this number rather unbelievable.
Since the data on penetrate at range is even more sketchy than that for 100 m I basically only looked at this.

Its also noteworthy that the Smk(H) has not been intended to be used at such distances. The pre and early war AT doctrine of the German army focussed on ambushing by fire at short and very short range. Which is propably why there is little data on lots of pre and early war German equipment for longer ranges.

EmericD said:

The US TM9-1985-3 from 1953 lists the capability of the SmK(H) as 19 mm of HHA at 91 m for 0° impact angle, and 13.5 mm at the same range for 30° impact angle.

In this case the SmK(H) would outperform the M993. Even though the numbers are lower than some other sources.
Regardless I think the 20 mm range for 0° at 100 m seems plausible to me for the SmK(H). The deviation around the 20 mm plate thickness are very likely due to different grades and kinds of steel being used as targets.

gatnerd said:

Thats really pretty remarkable. Nammo's current .338 is rated for 12mm @ 550 - 600m

Yes but I don't think it is really the case. I just mentioned the number because I found it. My fault I did not make that perfectly clear.

The .338 AP is a pretty tame loading. The SmK(H) is a super hot load. Just like the M993 the .338 AP suffers from the fact that its not really loaded hotter than the standart ball type ammo. Same pressure, same ME etc. The SmK(H) is not. It really goes above and behond. I guess it has not been pleasant to shoot it out of a rifle.
I think this is why the SmK(H) seems to be so good in comparison to more modern AP ammo. If the M993 or .338 AP would be hot loaded to the same extend as the SmK(H) they would certainly outperfom it.

schnuersi said:

In this case the SmK(H) would outperform the M993. Even though the numbers are lower than some other sources.

I agree that the SmK(H) is certainly outperforming the M993 at normal impact angle. 

The core is 12.5% longer, and the impact velocity at 100 m is probably similar (the M993 being ~30 m/s faster at the muzzle, but it's a light bullet with a low BC), so there are no reasons it can't outperform M993. By the way, the core of the SmK(H) is nearly as heavy than the whole M993 bullet. 

Against sloped armor, I think that the M993 will be more competitive. 

The penetration diagrams (as a function of the impact angle) of both the 15 mm H-Pzgr and the 30 mm H-Pzgr are very steep, much more than the slope of comparable steel core AP ammo, so I still think that those very hard WC-Ni cores are not performing "as well" as softer WC-Co cores against sloped armor (but it's just my opinion). 

I need to review again the literature of the "Stiletto" company, They claimed impressive AP capability for their rounds, but I don't remember the kind of WC they were using.

schnuersi said:

Regardless I think the 20 mm range for 0° at 100 m seems plausible to me for the SmK(H). The deviation around the 20 mm plate thickness are very likely due to different grades and kinds of steel being used as targets.

It's difficult to evaluate the effect of steel plate hardness on the penetration of a WC core bullet.

When you increase the steel plate hardness, you generally reduce the bullet penetration, but only to a point (I would say, around 360-380 Brinell). After that, the steel starts to behave like a brittle medium and WC bullet penetration is increasing again, mostly because steel hardness can't match the hardness of WC.

You can see this effect on the performance of the 15 mm H-Pzgr, which could defeat >52 mm of 100 kg/mm² steel (290 HB, below RHA) at 100 m, ~48 mm of ~150 kg/mm² steel (433 HB, above RHA) at the same distance, but "only" 44 mm of 125 kg/mm² steel (363 HB, representative of RHA).

Anyway, something like 19-20 mm of RHA at 100 m and 0° impact angle is a probable performance level for the SmK(H), so very similar to the .50 BMG steel AP.

schnuersi said:

If the M993 or .338 AP would be hot loaded to the same extend as the SmK(H) they would certainly outperfom it.

Well thats just the thing. In that test I shared, M993 was loaded into the .300 WinMag, and fired into the plate at an astounding 3,436fps / 1047m/s, which is 3,410ft/lbs / 4620j of energy. It still failed, and where the WW2 SMKH zips through.

Pretty massive boost compared to M993 standard which is 130gr @ 3000fps / 2600 ft/lbs / 3500j. 

The Time Traveler tungsten technology of the SMKH really is better then whats in M993, at least for surviving impact with ceramics. 

At basically all velocities I've seen tested by Buffman, the M993 shatters (even when it penetrates a plate it does so as a collection of fragments.)

The SMKH in both tests zips through the plate with relatively minimal energy loss, then zips through the clay backer behind the plate, and the core is never seen again - very suggestive that its not shattering or even that deformed by slamming into ceramic. 

Hence my belief that theres more at work here then core weight / length / energy. But rather that the formulation of the core, and its method of sintering (or alloying or magic), produces a much more ceramic impact resistant penetrator. 

EmericD said:

The penetration diagrams (as a function of the impact angle) of both the 15 mm H-Pzgr and the 30 mm H-Pzgr are very steep, much more than the slope of comparable steel core AP ammo, so I still think that those very hard WC-Ni cores are not performing "as well" as softer WC-Co cores against sloped armor (but it's just my opinion). 

This could be the case.
But again the type of steel used is of conciderable importance. If face hardened plates have been used it would have made a conciderable difference.

EmericD said:

but only to a point (I would say, around 360-380 Brinell).

Depends on the alloy and exact heat treatment.

EmericD said:

After that, the steel starts to behave like a brittle medium

If they are trough harneded.
Usually high hardness armor is face hardened. 500+ HB 10-3000 is pretty common for modern armor material. With extremes going up to 600 and these plates do not shatter... at least not if they are not made in China.
Armor penetration is extremly complex. Lots of variable and usually the information available to the public and especially on the internet doesn't define them. So its really difficult to compare.
This is also why a batch of steel for use in armor is being tested for its balistical properties befor being released for manufacturing.

EmericD said:

I need to review again the literature of the "Stiletto" company, They claimed impressive AP capability for their rounds, but I don't remember the kind of WC they were using

If you've got better / more in depth data on them that would be awesome.

Their website makes pretty astounding claims, it would be great to know how grounded in reality they are.

gatnerd said:

The SMKH in both tests zips through the plate with relatively minimal energy loss, then zips through the clay backer behind the plate, and the core is never seen again - very suggestive that its not shattering or even that deformed by slamming into ceramic.

I agree.  However, the plate had already been hit by three, very high velocity/energy rounds, I think the armor had been effectively destroyed before the SMKH test.

Notice that the SMKH bullet hit right on the edge of the back face bulge caused by the M993 bullet.  It seems very unlikely that the SMKH actually hit intact ceramic.

gatnerd said:

If you've got better / more in depth data on them that would be awesome.

In their report, Stiletto wrote that the core of their BS-13 bullet (13 grams / 200 grs, .308" or .311" diameter), is TSF22 which is ultrafine WC with a Cobalt binder.

This material is very hard (1930 HV30) and the density is 14.55 g/cm3.

Launched from a 7.62x51 mm case (or a 7.62x54 mm R case), the muzzle velocity is around 770 m/s and this bullet could defeat 20.5 mm of RHA / 2P / Armstal 500 steel plate at 100 m (several tests with different plates).

Launched at a MV around 840 m/s from a .300 WSM case, this bullet can defeat this same plate (20.5 mm) at 220 m.

For their smaller cores (5.45 mm / 5.56 mm) they are using VK8 (92/8 WC-Co).