From: watt-alan@net.yale.edu (Alan Watt)
Newsgroups: rec.guns
Subject: Re: Guns fired under water
Date: 12 Aug 92 23:33:37 GMT
Organization: Yale University, Computing & Information Systems



The following is derived from "NRA Firearms Fact Book", Second Edition,
Revised.  This book belongs in every gun-owner's library -- available
from the NRA publications division (703) 481-3340.

1. .22 fired under water
------------------------
A curious experimenter fired a .22 rifle under water at a target
3 feet away: "there were a few bubbles given off at each shot, but
there was little or no noise, and the target was hit with each shot.
There was no damage to gun or shooter".

Julian S. Hatcher then conducted some controlled tests.

2. .45 ACP fired under water
----------------------------
A M1911 service pistol loaded with 230 gr service ball cartridge
was mounted in a vise at the bottom of a 40" x 24" x 24" tank of
water.  Care was taken to insure the barrel was filled with water.

	"On firing (by remote control), there was quite a disturbance,
	with a lot of the water being splashed out of the tank.  The
	bullet passed successively through 16" of water, a 7/8" soft
	pine board, 6" more of water, and finally came to rest
	against a second board, making a deep dent in it.  The pistol
	did not quite eject the empty cartridge, but jammed with the
	slide part way open and the cartridge caught in the ejection
	opening.  The pistol was not damaged."


3. .30-'06 fired under water
----------------------------
The barrel and action of a M1911A3 service rifle were placed in the
same tank and loaded with an M2 service round (152 gr. bullet at
about 2800 f.p.s. muzzle velocity).  This time, as there was only
about 6" of water between the muzzle and the side of the tank,
four 7/8" pine boards were placed outside the tank in line with
the bore.

	"When the rifle was fired (by remote control), the bullet
	penetrated about 6" of water, the 3/64" steel side of the
	tank, all four boards, and disappeared inside a solid oak
	plank to a depth of about 2".

	"The bolt could not be opened by hand, but yielded easily
	to a few light taps with a rawhide hammer."

	"The case just back of the cannelure had expanded by about
	.032" and the primer pocket had opened up from the standard
	.209" to .228" and the primer was punctured so that a
	quantity of black smoke was observed to escape from the
	surface of the water near the breech when the gun was fired.
	The case and primer pocket expansion noted above are greater
	than those usually seen when a 70,000 p.s.i. high pressure
	test cartridge is fired in the same type of gun, so the
	pressure was probably quite a bit higher than 70,000 p.s.i.
	This is understandable, as the bore full of water would
	weigh about 385 grs., which is equivalent to adding 2.5
	additional bullets to the mass that the powder pressure
	has to move.

	"In spite of this additional resistance, the rifle showed
	no bulging of the barrel or other damage."

It would seem that if you intend to do any shooting under water you
should stick to handguns for safety, and pass up autoloaders in
favor of revolvers.

The next set of questions related to "how far under water do you
have to go to be safe from strafing with .50 BMG"?  The very
next section in the same book is titled "Bullet Travel in Water".

	"The Bureau of Ordinance conducted tests to determine
	depths of water necessary to give protection against cal.
	.50 and cal .30 AP bullets fired with service charges from
	a few inches above the water surface.  A target of 1"
	pine boards was suspended at various depths with its surface
	at right angles to the line of fire.  Complete penetration
	of the board was termed a lethal impact.

	"With cal. .50 fired vertically downward, the critical
	distance for complete penetration was found to lie between
	4 and 5 ft.  When firing at oblique angles (barrel inclined
	45 and 60 degrees from vertical), the lethal travel was
	reduced by approximately 1 ft. The ca. .30 was fired
	vertically only; complete penetrations wer obtained at
	1 ft. but not at 2 ft."


The author fails to note that in the case of strafing from aircraft,
the velocity of the bullet when striking the water will be augmented
by the forward speed of the aircraft, and will therefore carry a
lethal impact energy to a greater depth than the same gun fired
while stationary.

In any case, 6 feet down would seem to be safe, unless the attacking
aircraft were armed with crossbows :-) 

-- 

- Alan S. Watt
  Yale University			Computing and Information Systems
  Box 2112 Yale Station			(203) 432-6602