From: [n--hn--n] at [nosc.mil] (Norman F. Johnson)
Newsgroups: rec.guns
Subject: falling bullets
Date: 19 Apr 1995 22:02:44 -0400

Sean,

# I don't know what terminal velocity for a bullet is,  but I do know that
# it's still moving fast enough to cause injury.  Every year around the
# Fourth of July,  the newspapers in the Bay Area where I used to live
# would always have one or two stories of someone who got hit with a
# falling bullet.  The injuries were occasionally severe.  The speed is
# much less than muzzle velocity,  for sure,  but it's still dangerous.

Regarding the above from, Hatcher's Notebook:

"Among the many experiments carried out at Miami and Daytona, was
this same one of vertical firing.  It was desired to find out how
fast a bullet returned to earth and how dangerous such a bullet
would be if it struck a soldier after dropping from a great
height.  Many interesting things were learned from this test, and
they are given in detail in the "Official Report of Vertical Time
Flight for Small Arms Ammunition," in the files of the Ordnance
Department.  Much of the information given below is from that
source.

"At Miami the firing was done from a platform built in the shal-
low water of a protected inlet, where water was often calm.  A
frame was built to hold a machine gun tripod so that the barrel
pointed vertically.  Instruments were provided to check the angle
of the barrel, and the tripod controls permitted any necessary
changes in the barrel inclination to be made with ease and preci-
sion.

"Out of more than 500 shots fired after adjusting the gun--only
four shots hit the platform.  One of the shots was a service
30.06, 150 grain flat based bullet, which came down base
first...it left a mark about 1/16 inch deep in the soft pine
board.

"Two more bullets struck in a pail of water and left only a
perceptible dent in the bottom of the pail.  One struck the edge
of the thwart (seat across a boat, used by an oarsman) in the
boat, and left a shallow indent...The last two bullets were 175
grain boat-tailed.

"It was concluded from these tests that the return velocity was
about 300 feet per second.  With the 150 grain bullet, this
corresponds to an energy of 30 foot pounds.  Previously, the army
had decided that on the average, an energy of 60 foot pounds is
required to produce a disabling wound.  Thus, service bullets
returning from extreme heights cannot be considered lethal by
this standard.

"Most .30 caliber bullets seem to attain this final velocity, and
it doesn't make any difference how far they fall.  Even if a
bullet was fired downward from a very high plane, it would still
reach the ground at the same velocity.  That is because the
resistance increases very rapidly with increases in air speed.
If the air resists the motion of the bullet a certain amount at
300 feet per second, it will resist three times as much at 600
feet per second and nearly nine times as much at 1000 feet per
second.

"A 150 grain bullet weights .021 pounds, and when, in falling, it
reaches a velocity where the air resistance balances the weight,
the velocity of the fall will no longer increase.

"For a .30 caliber bullet of standard experimental shape, having
a pointed nose of two caliber radius, the air resistance on the
nose at 2700 fps. would be about 2.3 pounds; at 2000 fps. 1.5
pounds; at 1500 fps. .89 pounds; at 1000 fps. .17 pounds; at 500
fps. .04 pounds; at 350 fps. .025 pounds; at 320 fps. .021
pounds, balancing the weight of the bullet and stopping any
further increase in velocity in the case of a falling bullet."

     ****************************************************

God Bless!

Norm