1984 7.62x51mm NATO SLAP Prototype


#1

I was lucky enough to pick up this box a few years ago from a retired person that worked for Winchester / Olin in 1984. He said these were from the factory and used in testing.
Note:
Unlike most production which states “SLAP” on the head-stamp these state: “WCC 84” on the head-stamp (1984) before production began in 1985. They also have a red primer sealant on the crimped primer, and the sabot is the translucent and same type used in the SLAP production.
I have no doubt these are real and were used in the testing phase.
My question is why have the projectiles darken vs. the normal steel finish? They are magnetic and most likely tungsten. Maybe tungsten darkens with time? any ideas?

Thank you,
Dave Call
A Call to Arms,LLC
ammo-one.com


#2

Dave

Tungsten is gray in color, which could account for the color of those penetrators. But, if they are magnetic, that means the tungsten is alloyed with other metals because pure tungsten is not magnetic.

Most AP bullets are simply hardened steel and even the so-called tungsten AP bullets of the WW II years were actually ony about 5% tungsten. I believe the modern AP that is made overseas and imported for our military (M993 and M995) are either tungsten or an alloy.

Ray


#3

Thanks Ray, I did not know Tungsten was not magnetic, I learned something today :-) Most likely Tungsten steel. I will have to take a metallurgy coarse, but at my age I will most likely forget it, after I learn it :-)
Best,
Dave


#4

[quote=“RayMeketa”]Dave

Tungsten is gray in color, which could account for the color of those penetrators. But, if they are magnetic, that means the tungsten is alloyed with other metals because pure tungsten is not magnetic.

Most AP bullets are simply hardened steel and even the so-called tungsten AP bullets of the WW II years were actually ony about 5% tungsten. I believe the modern AP that is made overseas and imported for our military (M993 and M995) are either tungsten or an alloy.

Ray[/quote]

Ray, pure Tungsten (not magnetic) is not used in projectile cores. The material used in AP cores is Tungsten carbide (which is ceramics and no metal actually - I do not mean the 5% or thelike Tungsten alloys). The Tungsten carbide of AP cores actually is magnetic (as it holds other metals too), just not as magnetic as steel.


#5

Yes - the cores were described as “tungsten steel” which has confused a lot of people. AP performance was not significantly better than other steels.

Tungsten carbide - which (other things being equal) increases the penetration by about 50% compared with steel AP cores.

I can think of one: the developmental 6.5 x 25 CBJ “ball” saboted round uses tungsten.

I understand that some of the latest APFSDS tank gun cores use more exotic alloys of tungsten, in an attempt to replicate the performance of DU.


#6

Tony, thanks for the update!

Good to know the approx. ratio of steel alloys vs. tungsten carbide cores.

6.5 x 25 CBJ “ball”: what purpose would this serve? As far as I know tungsten itself is not hard at all. So why making it so expensive when lead would do the same?
Unless environment is a factor but this will make the rounds unaffordable I’d say.

Can you say more about the “exotic tungsten alloys”? Sounds interersting.
In June (ES 2012 Paris) I had a talk to the head of development of Plansee (a French company):
plansee.com/en/About-us-Prod … ce-183.htm
He mentioned a tungsten alloy with a high percentage of tungsten in their penetrator alloys (if I recall right like 80%+).


#7

[quote=“EOD”]6.5 x 25 CBJ “ball”: what purpose would this serve? As far as I know tungsten itself is not hard at all. So why making it so expensive when lead would do the same?
Unless environment is a factor but this will make the rounds unaffordable I’d say.[/quote]

Tungsten is more dense than lead (by 1.7x) providing improved velocity retention for long-range performance. The density also makes it a good hole-puncher even without hardening. The pic below shows the effect of 7.62mm M80, 5.56mm M855 and the 6.5x25 CBJ ball round on 9mm Russian LAFV armour plate:

Tungsten costs 20x as much as lead, but the CBJ penetrator is very small (only 4mm diam, and weighs 2 grams/31 grains) plus given the relatively small combat use of PDWs and pistols would probably keep the cost acceptable.

Various other heavy metals are involved, I believe, although it’s difficult to find specifics. The British 120mm L28A1 is said to use a tungsten-nickel-iron penetrator, the German DM 53 and DM 63 use a penetrator of “Rheinmetall Tungsten IV” , also known as WSMIV, but the rest just say “tungsten alloy”. The subject has been discussed in the past on the Tanknet forum, but you’ll have to search for it: 208.84.116.223/forums/index.php?showforum=18


#8

What distance was that plate tested at?


#9

Tony, at 2 grams it sounds reasonable then + we may assume this will be no regular issue by the million.


#10

I don’t know for sure, but probably only a few metres.