The Elk County advocate. [volume] (Ridgway, Pa.) 1868-1883, 1876-09-28
RIFLE SHOOTING.

Elevation ana wilma AuoWnnce-'Euectt
of Atmospheric Resistance on the Pro-
iectiies.
Notwithstanding the popular interest
in the rifle contest OF Oreedmoor, very
few general readers, says the New York
Herald, have any correct idea of the
technique of rifle shooting and the mar
velous perfection to which it has been
brought. OF course the ordinary OBJ
server forms some estimate of the diff
Guilty OF hitting the small black speck on
the target which is called the bull l's-eye
and is amazed to see the marksmen put
ting bullet after bullet into it with q
precision which approaches the miracu-
lous. He measures the first by reference
to the great distance of the markaman
from the target and the size of object
aimed at, and the other he regards as
wonderful because of the skill displayed
in the face of the difficulties already
named. Beyond this he forms no opin-
ion of the craftsmanship and contents
himself with applauding the results as
deserving of great praise.
Take mau of the steadiest nerve and
the keeifest eyesight, but possessing no
knowledge of the laws governing the
flight of proiectiles, and put in his
hands the most perfect rifle that can be
manufactured; then place him before
the target at say five hundred yards,
and the chances are that in nine shots
out OF ten he will fail to hit the target at
all, not to say the bulls eye. This is
because there is a knowledge necessary
independent of mere good aiming and
n1a ic,n 10
tent himself with lying down and
steadily directing his rifle at the bulls
eye without any regard to the operation
of the forces acting on ball during its
flight, and would expect that it should
follow direct line to the object aimed
at.
But in this he would be entirely at
fault, and his eye would not be greeted
by the markers disk at the butts, show
ing that the shot was "on." A puff of
dust from the ground considerable
distance i'll front of the target would in
form him that his bullet fell short of its
mark. On inquiry as to the cause of
his failure he would receive from those
who knew all about it the following in
formation:
When bullet leaves the muzzle of a
rifle in its flight toward the target three
forces act upon it and influence its
movement until it is checked by striking
a resisting object. The first is the force
Of propulsion, impaired in the gun by
the energy of the expanding LAS, gene.
rated by the explosion of the charge.
This force receives direction from the
barrel of the gun, and if no other force
acted on the ball it would travel on an
exact line in continuation of that of the
axis of the barrel. The second force is
that of gravity, which tends to draw the
bullet downward toward the earth with
q constantly increasing velocity. Con.
sequently, instead of following straight
course coincident with the axis Of the
barrel it falls continuously from that
line during it's fight. The third force
is that represented by the resistance OF
the air, which tends to retard the bullet
i'll its progress toward the target and
acts in proportion to the square of the
velocity of the bullet and to the density
OF the atmosphere itself. Thus, instead
of traversing along the direct Or the
shortest line to the object, it follows @
course which is theoretically parabolic
but actually, and by reason of the at.
mospheric resistance, modification oi
that. curve.
In order, therefore, to insure the
flight of the bullet over the full distance
between the rifle and the target it is nee
essary to elevate the direction of the
barrel, so that the projectile will be
raised during its flight sufficient height
over the plane in which are located the
point of departure aud the object
sought to be hit to compensate for tht
loss by gravitation.
To regulate the angle, tangent scale
is fitted to the breech OF the gun, aud tC
this scale is attached the movable rea!
sight with which, with the vertically i'm
movable muzzle sight, the line of sigh
or aim is determined. The scale is di
vided into degrees, minutes and seconds
J the latter subdivision being obtained b,
means of vernier scale attached fu
the purpose. The fine division of tin
tangent scale is necessary in order Il
! regulate the changes in elevation re
quired for variations of range and th
resistance of the atmosphere. In tn
former case, let it be supposed that
marksman hits the bull 8, eye at an eigh
hundred yards range, with certain ele
vation of the rear sight on the tangen
scale. Ii he desires to hit it again a
$50 yardshe must increase the elevation
and decrease it for distance of II
yards. Thus the utmost accuracy CA
only be attained by fine adjustment Q
> the sights.
The influence of the wind on tn
fight of a bullet is very great, and, whe
the wind is variable, is constantly chang
ing. On perfectly calm day at Greed
7 moor the line of sight is in the sam
vertical plane as the line of fire; that is
the marksman adjusts his muzzle si2l
to correspond exactly in relation to th
breech sight with the axis of the riff
barrel. He shoots dead on" as it
l termed, making no allowance for th
force OF the wind. If, however, win
is blowing in the same direction as til
line of sigdt that is toward the target
the elevation of the breech sight mus
be lowered in proportion to the force {
the wind, because the moving air cul
rent has tendency to lift the ball, nc
actually, but relatively, by delaying th
fail due to gravity within the period {
! flight. On the other hand, if the win
blows toward the marksman the elevi
tion must be raised to compensate fo
> the increased resistance created by tn
: wind to the progress of the bullet, whic
is in addition to the normal resistance {
. the air at rest.
When the wind blows across the lin
D of fire it causes the bullet to drift in th
same direction as the wind blows, an
while it may not necessitate an alters
I tion of elevation it compels the rihema