From: ahahma@utu.fi (Arno Hahma)
Newsgroups: rec.guns
Subject: Re: Uranium penetrators (was: Are Portable MIniguns Possible?)
Date: 13 Nov 1994 11:32:03 -0500

In article <3a13kn$4bg@xring.cs.umd.edu>,
aaron r clements <arc@alumni.caltech.edu> wrote:

#11.3437 g/cc for lead; although my CRC doesn't have uranium listed in 
#its hardness tables, I suspect, based on melting points, that depleted
#uranium is also quite a bit harder in addition to the density factor.

Pure U is about as soft as lead. However, certain elements make uranium
very hard when mixed with it. That kind of behaviour gives you a good
advantage: adjustable hardness and brittleness. That is pretty
hard to do accurately with tungsten, as you have to work with powder
metallurgy.

#All of which is more than you probably wanted to know.  :)

You forget a couple of most important things.

First, uranium can be melt cast and alloyed. Compared to most high
density materials, this is a great advantage and makes fabrication a
lot cheaper and easier.

Second, uranium is dynamically self sharpening, when alloyed suitably.
Tungsten is not. That means, on impact, the penetrator rod nose
fractures in a way that makes the nose sharp again.  This kind of
behaviour significantly reduces the energy required for penetration and
gives the uranium penetrator a large advantage over tungsten, even
though tungsten is as dense and strong as uranium.


ArNO
    2

Newsgroups: sci.military
From: Arno Hahma <ahahma@utu.fi>
Subject: Re: APFSDS-T
Message-ID: <C5J9sz.HEF@law7.DaytonOH.NCR.COM>
Date: Thu, 15 Apr 1993 16:29:22 GMT

From Arno Hahma <ahahma@utu.fi>

In article <C5DL4z.I00@law7.DaytonOH.NCR.COM> "Mark J. Stock" <mstock@engin.umich.edu> writes:

>reserves of heavy elements in their country.  In America, because Uranium
>is not quite as easy to get, they use Tungsten Carbide, a harder and just
>as massive metal.

I don't think anyone uses carbides, as they are very brittle. Using a
metal alloy is a better choice.

>	The russian!s penetrators are wider, but the US!s are longer (I think).

Possible. The russian penetrators I have seen were all much wider than
the western counterparts. The russian projectiles were of a
significantly lower quality material, too.

>I also think that with the new tanks coming out, the American round will
>travel faster, too.

I doubt. The Rheinmetall 120 mm gun fires at about 1650 m/s while the
125 mm russian gun fires at 1890 m/s. There is quite a difference
there. The ammo weight is very close to each other.

>	BTW, the specific gravity of Uranium and Tungsten is 19, Gold being the
>only other element as dense (19 too).
>	If someone know any of this for sure, please tell us!

While the theoretical densities of those two metals are almost equal,
it is an entirely different matter, what the densities are in the
projectile.  Tungsten, being a very high melting metal, can only be
fabricated by powder metallurgy. That means, you _never_ reach the
theoretical density. In addition, pure tungsten is soft, just like
construction steel, you can file it, cut it etc. Despite of that, it
is brittle - just try how weak a lamp filament is compared to a wire
of the same thickness and made of say, copper or steel. Tungsten is by
no means an ideal material.

To correct the problem, you have to get the material more ductile or
harder or both. This is done by alloying. If you choose anything less
dense than tungsten itself as the additive, you end up with an alloy
less dense.  Unfortunately, there are barely choices denser than
tungsten, so you have to compromise. The final density will be
something in the order of 11 to 15 g/ccm. The russians are closer to
the lower and the western closer to the upper limit.

With uranium, you can do it much easier: by casting. Uranium melts
relatively low and certainly dissolves suitable additives to reach
enough hardness. Uranium is also very ductile by itself, so you only
have to worry about keeping that property, not gaining it. As a
result, it is easy to reach densities in excess of 15 g/ccm, despite
of problems with the casting process (such as keeping the air out of
it). I think uranium has not been introduced earlier, as they have not
found good additives for getting it tough enough. As a pure metal, it
is soft like lead, which is really not strong enough for the
accelerations needed.

I have these nice, cylindrical paperweights on my table, shaped,
strangely enough, ogivally at one end. One is supposed to contain
about 90 % W and the rest something ferrous and it also has some odd,
5-pointed star shaped stamps on its ogival end. It's quite heavy,
density as high as 11,7 g/ccm and da** hard. Then there is this other
paperweight, without the mentioned stamps and much smoother and nicer
looking and extremely hard - it even scratches quartz!. It seems to
contain 89 % of W, 10 % of Ni, the rest being too long to write in
this limited bandwidth. The other weight is also very heavy having a
density of 14,8 g/ccm. Then there's this third one, which I don't have
on my desk... ;->.

>Mark J.Stock

ArNO
    2