From: gherbert@gw.retro.com (George William Herbert)
Newsgroups: sci.military.moderated
Subject: Re: P90
Date: 29 Oct 2000 18:39:38 -0800

Steve Won <swon@uiuc.edu> wrote:
>> Now, myself, I'd rather have a M4 (with full-auto option) than a MP-5
>> pretty much any time. Not sure about the P90 - looks good on paper but
>> it's designed as a PDW rather than a frontline weapon.
>
>I can think of one place where I'd rather have the MP5: when I'm worried
>about overpentration, such as when I'm inside a structure with thin walls.
>Like a house.

Except that this is in fact a small arms urban legend.  Take a look at
the following set of rounds and guess their US wall penetration (2 layers
of gypsum wallboard with 2x4 standoff, assuming the projectiles hit
between not on the studs):

5.56mm hollowpoint
5.56mm FMJ
9mm frangible
9mm hollowpoint
9mm FMJ

Now order them in the order least to most likely to penetrate specified wall:

9mm frangible
5.56mm hollowpoint
5.56mm FMJ
9mm hollowpoint
9mm FMJ

As it turns out, most 5.56mm ammo, *including* FMJ military ammo,
will fail to penetrate the far side of the wall.  5.56mm hollowpoints
were tested as reliably being stopped by the wall, and FMJ as fairly
reliably.  9mm hollowpoints often fail to expand or fragment in the
first wallboard and thus penetrate the second one, though they are
usually stopped by the wall.  9mm FMJ penetrated the best.  The only
9mm ammo reliably stopped in a wall is frangible (Magsafe, Glaser, etc).


-george william herbert
gherbert@retro.com