MINUTES OF PROCEEDINGS OF 
U2 
Let us assume OC as the required parabolic curve, and let OM drawn 
through the origin of the parabola, perpendicular to its axis, represent the 
length of the bore to be rifled. The tangent at C makes an angle with 
OM or AB equal to the angle of rifling at the muzzle, and cuts off (by the 
property of the parabola), OA on the axis equal to the abscissa OK. 
Again, 
/. MC = MB. 
7r x calibre 
BC ___ ___ 
AB number of calibres x calibre number of calibres 
3-14159 
in this case = 
45 
but AB given length to be rifled is 107*5 ; 
■an 3-14159 x 107*5 „ K 
“ -45- = 7 ’ 5j 
^(=x)= 3 ' 76 - 
Having thus obtained the abscissa or X corresponding to the given 
co-ordinate OM, we can find the abscissa at any other measured distance 
on OM, and hence any number of points in OC. 
Lor, according to the equation of the parabola. 
— = y? which is true for all points; 
X 
. OJ / 2 
"MO 
. y 3 __ . 
” ~x ~MC J 
MC X y 2 
OM 3 * 
A practical way to get the curve, is to divide the distance OM into any 
number of equal parts, say ten— 
then the height x corresponding to any division, the 4th for example, is 
obtained thus :— 
a? MC 3*75 
