THE ROYAL ARTILLERY INSTITUTION. 
129 
Table XII. 
Abstracts of Experiments made to determine the Effect on the Initial 
Velocity oj diminishing the Lead on the \2-pounder Armstrong 
Projectiles. 
6B|h 
4 
£ 
Projectile. 
Yelocity 
Initial 
Sh £ 
o 
at 
Charge. 
Remarks. 
II 
*o 
30 Yards. 
Velocity. 
o 
Weight. 
Diameter. 
lbs. oz. 
lbs. oz. 
ft. 
J 
4 
1 8 
11 9 
3*074 
1238*3 
1248*2 
C Shell fired under normal cir- 
l cumsfances. 
I 
fSame shell reduced to the di- 
!i 
2 
„ „ 
„ „ 
3*010 
1200*2 
1209*7 
J ameter of 3*01, with the ex- 
] ception of a ring at the base 
*L 
2 
” ” 
3*010 
1163*7 
1172*8 
L *25 inches broad. 
Same shell reduced throughout. 
29. The experiments with the Armstrong 12-pr. having been chiefly 
carried on with the same gun, the initial velocities obtained under 
similar circumstances become a measure of the variability, in strength, 
of the service gunpowder, and it is somewhat surprising to find so 
great a variation in powder recently made and professedly of the same 
make. For illustration of this remark, I may point to the differences in 
initial velocity exhibited in figs. 1 and 2. In this case, it is true, the 
results were obtained from different guns; but under similar circum¬ 
stances, these guns were found to give nearly identical velocities. Another 
even stronger case, however, may be taken from the velocities given on 
different occasions by the gun numbered 1050. Thus, on the 12th 
March 1861, with a service charge of powder marked (A. 4, W. A., 
5/9/60, lot 288), the initial velocity was found to be 1114*8 feet, while 
under precisely the same circumstances, on the 15th March 1861, with 
powder marked (A. 4, Hall and Sons, 11/7/60, lot 2), the initial 
velocity was 1248*2 feet per second. I may observe that with the 
Armstrong 12-pr., when the same powder is used, the variation in 
initial velocity is very slight, the extreme difference in 10 rounds 
rarely exceeding 20 feet. 
30. On actual service it is obvious that the strength of the poivder 
may be expected to vary considerably more than is here indicated ; 
and I venture to draw the attention of the Select Committee to this 
point, as one seriously affecting the precision of rifled, or indeed of 
any guns, and as a case in which the electro-ballistic apparatus might 
be most advantageously employed. 
31. My attention during these experiments was early drawn to the 
ranges obtained at P. B., and at small angles of elevation, with the 
12-pr. Armstrong. These ranges considerably exceeded those of the 
smooth bored field service guns, although, of course, the initial velocity 
in these latter is very much higher. I therefore took the usual steps 
for ascertaining the “ angle of departure,” and, as much additional 
trouble was not entailed, I also made arrangements for ascertaining 
the ordinates at various points of the trajectory. It will be seen by 
these observations that the angle of projection of a projectile fired from 
a 12-pr. gun, accurately laid with its bore horizontal, varied from 
0° 23' 30" to 0° 28' 28", the mean angle of projection being 25' 33", 
while in the same gun fired with an elevation of 30', the angle of 
projection varied from 47' 0" to 49' 6", the mean angle being 48' 18". 
