Fulton County tribune. (Wauseon, Ohio) 1883-1925, 1918-05-03

above the level of the gun there is Il
ten-rnile wind blowing straight across
the line gun target, the thermometer
is up to 50 and the barometer has
dropped to 90 viii the prOjectile hit
the target now? Not unless you cor
rect the elevation Of the gun for some
of these conditions and it's laying for
the others. How are you going to
do It?
First, you must find the force with
which your projectile cleaves the air.
This is called the ballistic co-efficient,
and is reduced by a simple formula to
a figure. Knowing the weight of the
projectile, its form and it's diameter
the ballistic co-efIicient is easily cal
culated.
The Air as a Check.
You have now taken the first step.
You have the force of projectile to
penetrate the atmosphere under stand
ard conditions. But this force varies
with the atmosphere. On a heavy
muggy day the atmosphere is dense
and you will be surprised the check.
ing effect it will have on your projec.
tile. BY means of elaborate tables one
can find just what this effect is, and
we apply It to the original formula
Also In the atmospheric factor is in
cluded the temperature, for in hot
weather our powder charge when ig
nited exerts more strength in decom
posing into gases than it does on q
| cold day.
So far so good. What about this
troublesome wind that is blowing? II
It blows against the proiectile II
checks It; If with it, it helps it along
So we have two varying factors
which the ballistician juggles by utiliz
ing trigonometry until he gets them in
terms where he can once more change
his balllstic cO-efficient, making Il
larger or smaller as the wind i'm
pedes or accelerates the projectile.
Not quite so easy as you thought, Il
it? But we are not through yet.
We know that under range table
conditions our propelling charge ha.
a force that gives the projectile al
initial velocity of so many foot sec
onds, say 2,250. But our powder ha,
been stored In a dugout whose tenn
perature is not normal, so by more fig
uring we find out just what this rea
velocity for the day is. Now we cal
begin to figure what elevation tn,
gun must have TO travel that 10000
yard path to the target.
BY dividing our old friend c, as tn,
ballistic co-efficient is termed, by tn
distance in feet that the projectil
must travel, we get a reference mum
ber. This number we take with u
and bury our noses in more tables un
til we find opposite this number in
column headed by the muzzle velocit
another number. This number, multi
piled by @ again, gives us the sine o
twice the angle Of departure.
quick glance into a table of logaritf
mic sines gives this to us, and dividin
by two we have figure in degrees an
minutes that represents the angl
which the gun must be elevated fror
the horizontal to send its projectil
10000 yards today. Wait a minut,
Our target is 200 feet above the levC
of the gun. Also because of the cur,
ature of the earth this 200 feet heigf
has been reduced somewhat. SO ono
! more we delve into mathematics to CO..
, rect the curvature of the earth an
height of site of the target. The n
suit we subtract from the angle fOunt
} and this time our gun is ready fc
! business. Is it? No: it is not so eas,
The Influence of the Rifiing.
! Every rifled piece of ordnance in
parts twist to its projectile, an
this twist causes the projectile to dev
, ate from its course. In our service TIL
, deviation, called drift, is to the righ
! and Is In ratio with the range. 1t
= constant, therefore, for each range. an
{ we find it very easily, either by mat
ematic computation or from drift L
: bles. Also we go back to our wir
{ problem and find what effect the wir