<7 
i 
20 O. N. Rood on Elongated Projectiles. 
Tt will be seen from these experiments that a ball of the above 
model, and 1°67 diameters in length, must make 280 revolutions 
r second to ensure its accurate flight, when discharged with an 
initial velocity of 1100 feet per second; what rate of revolution 
would be necessary to sustain it point foremost, were the initial 
velocity different, is another question, and one which will pres- 
ently be noti 
tus examine the case of a ball slightly longer than the 
above. Rifle No. 2 was now employed, its ball was slightly 
blunter than No. 4; it had often made excellent practice at 220 
and 500 yards, 
Ball No. 2. 
1°77 diameters in length. Weight 10501 grains. 
Taitial Ve locity. | No. Rev. | Distance. [Point >premost. Sidewise 
1051 298 165 ft. all 
1199 340 |660,“ | all | 
By a comparison with the last table, it will be seen that this 
slight increase of the length has carried with it the necessity of 
50 additional revolutions per second. The lowest initial velocity 
have ever actually employed in this rifle for target practice 
was 1774 feet, the highest 1917 feet, so that the number of revo- 
lutions made by the ball in actual practice was either 503 or 543. 
Balls 2 and 25 diameters in length. 
A longer balf for barrel No. 4 was now constructed : its weight 
was 141°5 grains, diameter ‘36 in., length ‘74, so that it was in 
” fact 2°05 diameters in length. The following results were 
obtained : 
Ball 2:05 diameters long. 
Initial Velocity. No. of Rev. Distance. 
968 BAS 05 ASE all sidewise. 
The above shows that with this model 269 revolutions are al- 
| oo insufficient, if the initial velocity be as high as 1063 ft. 
he length of the ball used in the Swiss federal rifle is 1-0039 
inches, its diameter 0-41 inches, or it is 2-44 diameters in length, 
Weight 257 grains, weight of the charge 62 grains, Making use of 
the British empirical formula V = 1600 4/ 2”, we have the ini- 
w 
tial velocity = 16004/ ; o = 1861 ft., and as the twist is one 
turn in three feet the ball leaves the barrel making 453 revolu- 
tions per second. 
ie 3 
