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).

Great info as always, thank you. Based on those specs, does that seem to offer comparable or better performance to the ADVAP style exposed tungsten tip bullet from the GD slide?

...

Similar to M993, they are binding it with Cobalt (as opposed to the Nickel of the SMKH and you said SLAP). 

I wonder whether their core is similarly vulnerable to shattering on impact with ceramics as the M993 core is? 

Heres the best video example of M993 shattering. It penetrates the plate, but enters the gel as multiple fragments, rather then a solid core.

Video should begin at 3:00

YouTube

Tungsten Core M993 and API B32 VS @AR500 Armor® Level IV - Super RARE!

Aimed Research: https://goo.gl/SgOpkGAR500 Armor: https://alnk.to/9mgN4JxFacebook: https://www.facebook.com/BuffmanVids/Instagram: https://www.instagram.com/...

My concern is these cobalt sintered projectiles show very good performance on steel (M993 is pretty solid on steel) but may shatter when encountering harder ceramics. 

gatnerd said:

My concern is these cobalt sintered projectiles show very good performance on steel (M993 is pretty solid on steel) but may shatter when encountering harder ceramics.

Unfortunately, I can't answer that question.

I've got a very effective ammo lot of 7.62x51 mm DM151 (high density WC-Co core, MV around 880 m/s from a 22" test barrel @+52°C, and 855 m/s @+21°C) that will be tested against ceramic armor, but not before 2023.

Against RHA, an exposed tip .277 Fury ADVAP (main hypothesis: a 32 mm long WC core, a MV of 3000 fps and a 0.29 C7) could probably defeat someting like 29-30 mm of RHA at 100 m, and 16-17 mm at 600 m which is (from my limited experience) the "entry ticket" to expect being able to defeat lvl IV ceramic armor.

EDIT : with the above set of hypothesis, a .277 Fury ADVAP is duplicating the performance of the XM948 SLAP up to 500 m, and is slightly better after 500 m due to it's higher BC.

gatnerd said:

My concern is these cobalt sintered projectiles show very good performance on steel (M993 is pretty solid on steel) but may shatter when encountering harder ceramics.

Why concern? In the picture the penetrator fragments look awefully effective.
It might even be intentional to get good behind armor effect?

One of the main functions of the Cobalt in the WC Co sinter mix is to increase the resistance to impacts. To improve the flexibility and ductility of the material. Prue WC is very hard but very brittle. This is why there are different mixtures of WC and Co available for different uses.

I am not convinced that a WC-Ni-Fe mixture would give better shatter resitance.

The material EmericD mentions, TSF22, also is a tool grade WC-Co mix. With ~8 % Co. Special about it is the super fine graine structure. Its about as hard as you can get without using pure WC.

What I find intresting is that is seems nowadays the ammo manufacturers just use tool grade WC materials they can purchase on the market. My guess is they don't even shape the penetrators themself. They just order them from a company specialised in sintering. The ammo manufacturers just assemble the cartidge from parts that are delivered to them.
This of course has implications for the performance. The tool grade WC materials are all a compromise tailored for one specific application. Which is why milling workshops usually have a selection of different cutting tools. But armor penetration is a very complicated process and unlike milling in a workshop the surounding factors are not known in advance and can not be controlled. So its virtually impossible to select the ideal penetrator material in advance. Actually it seems necessary to pick the best compromise that will allmost allways work in a usefull way.
Getting trough hard ceramic plates but shattering and working fine against steel armor might be such a compromise. Allthough for the M993 I rather think penetration of ceramic body armor has not been a factor at all concidering the time of development.

schnuersi said:

Why concern? In the picture the penetrator fragments look awefully effective. It might even be intentional to get good behind armor effect

The issue is that Ceramic plates function by shattering penetrators into 'un-piercy' sized fragments that can then be caught by the UHMWPE backer. 

If the penetrator doesn't shatter (or if the penetrator only shatters mildly in the case of that test) after passing through the ceramic gauntlet, it can then zip through the UHMWPE backer.

So they key for Ceramic defeat is a penetrator that can survive its impact with the ceramic to the fullest extent possible.

In that M993 test, it was able to make it through. But many other M993 tests from Buffman have shown failure due to shattering.