Topic of the Month: June
2002
Comments on a Bullet's
Travel in Water
A question we are sometimes asked is,
how far will a bullet travel in water and are objects underwater really safe from rifle
fire?
The answer to this question depends on many
factors, such as angle of fire, bullet shape, bullet nose construction and muzzle
velocity. Full-jacketed military bullets give better penetration in water than soft-nose
bullets. Soft-nose bullets often expand or break up. Bullets fired at a steep angle will
enter the water while bullets fired at shallow angles may glance from the surface and fly
off in unpredictable directions.
Near the end of World War II instances were
reported of navy survivors, adrift in the ocean, being strafed by enemy aircraft. When
attacked, the natural defense was to submerge. But did the few feet of water actually give
any protection against machine gun fire?
The Bureau of Ordnance conducted a series
of tests to determine depths of water required to give protection against .50 caliber and
.30 caliber AP bullets fired from a few inches above the surface of the water. A target of
1-inch pine boards was suspended at various depths with their surface at right angles to
the line of fire. The Complete penetration of a board was considered a lethal impact.
When the .50 caliber bullet was fired
vertically downward, the critical distance for complete penetration was found to lie
between 4 ft. and 5 ft. Firing at oblique angles of 45 to 60 degrees from the vertical
position reduced the lethal bullet travel by approximately 1 ft. When the .30 caliber
bullet was fired vertically downward, complete penetration was observed at 1 ft., but not
at 2 ft. Based on these observations a person must be submerged at least 5 ft. to feel
reasonably safe from .50 caliber machine gun fire and at least 2 ft. for .30 caliber
machine gun fire.
Watch our web site for the next
month’s topic of interest. Until then, shoot safely and know where you bullets are
going.
Sincerely,
The Ballistician
< Return
