From: bbx!bbxrbk!russ@unmvax.cs.unm.edu (Russ Kepler)
Newsgroups: rec.guns
Subject: Great Armor Plate Shoot
Date: 22 Dec 92 15:06:23 GMT
Organization: russ at home in Albuquerque New Mexico

The Great Armor Plate Shoot of 1992

The Armor Plate shoot finally came through, after 3-4 attempts aborted
by snowfall, on Saturday December 19 1992.  The Armor Plate Shoot was
an attempt to once and for all settle the Ackley claim that a .220
Swift could and would penetrate the armor plate found on the front of
a 1/2 track vehicle.

The calibers fired included .30-06 (M1 Garand), 7mm Magnum and
7.62x39.  In the absence of a .220 Swift Remington .30-06 Accelerators
were used as a replacement - .220 Swift factory ammo should clock
3650 fps at the muzzle, the .30-06 Accelerator is said to clock
4080 - giving the Accelerator rounds a slight advantage[1].

In case anyone out there isn't familiar with the .30-06 Accelerator
the "bullet" in this round is a normal softpoint .224 bullet in a
"sabot", or shoe.  This sabot holds the bullet during it's travel
down the barrel until it exits the bore whereupon the sabot departs
the bullet.  The advantage in using a sabot is that it makes it
possible to file a sub-caliber bullet in a larger bore and achieve
much higher than normal bullet velocities.

The top of the plate was placed at an angle of approximately 30
degrees back from the vertical and rested on a metal brace set on the
ground.  No serious effort was made to resist the motion of the plate.

All firing was done through a Crony Chronograph[2] in an attempt to 
get bullet velocities.  The chronograph was placed approximately 12
feet in front of the firing position.  Approaching darkness made it
difficult to get chronograph readings.

The .30-06 Armor Piercing (WWII vintage) round completely penetrated
the plate, and no sign of the penetrator could be found.  The path of
the penetrator seems to have been completely normal and parallel to
the ground.  The size of the hole was very close to the expected
penetrator diameter - .25".  There was a small lip on the entry and
exit hole.  The round clocked at 2804 fps.

The .30-06 Accelerator failed to penetrate the armor in either of 2
shots.  The shots did crater the armor to a depth of .25" and .3" and
crater diameters of .6" and .55".  The shots fired raised a high lip
about the craters and bulged the rear of the plate .065" and .055"
respectively.  The chronograph failed to register either of the
shots[3].

Interestingly enough the 7mm Magnum (.284") firing a 125 grain bullet
did almost as well as the .30-06 Accelerator.  The crater from the
firing was .2" in depth and .5" in diameter.  There was no significant
lip around the hole and a large bulge on the rear of the plate about
.090" high.  The shot clocked at 3314 fps.

As a point of interest we fired a round each of East German 7.62x39
and Chinese steel core neither of which did much more than a light
scoring of the plate.  This surprised both of the shooters after
hearing of damage done to facilities from the inexpensive steel core
ammo.  This ammo clocked 2520 and 2440 fps.

A .308 caliber AP round (1972 Israel production) was fired at the
plate and penetrated, but failed to clear the plate.  The penetrator
was left sticking out the back of the plate and into my target stand.
The penetrator seems to be welded to the plate and cannot be removed
from the plate (and attempts to hammer it out from the rear simply beat
up the hammer face - a result expected in hindsight).  A small piece
of jacket material is still visible in the rear of the entry hole.  It
seems likely that it would have penetrated fully if it hadn't hit the
target stand.  This round clocked at 2790 fps.

One more round was fired - a .375 H&H Magnum.  This round didn't
penetrate significantly but was the only round fired that flipped the
plate over the holder, an impressive display of momentum transfer. 
The round clocked at 2734 fps.

Further firings will be done including a real .220 Swift and a .17
Remington.  We really tried to get SS109 for a test firing in a Mouse
gun, but failed to suceed in finding any.  When the data is available
I'll try to post it.


[1] - data from Gun Digest 1993.  The data in the NRA Firearms Fact
Book gives a .220 Swift 4110 fps with a 50 grain bullet.

[2] - Just above, actually.  Through would have been a bit too low.

[3] - I'd suggest to anyone performing this experiment to remove the
screens from their chronograph - the discarding sabot seems to break
up quickly in flight, but not quite quickly enough to fail to act as a
bunch of shotgun pellets to the chronograph...


-- 
Russ Kepler, posting from home   bbxrbk!russ@bbx.basis.com
Will hack unix for food