THE EOYAL ARTILLERY INSTITUTION. 
359 
ON THE 
PRESSURE REQUIRED TO GIVE ROTATION 
TO RIFLED PROJECTILES. 
BY 
CAPTAIN NOBLE, &c. 
(Late 1i.A.) 
1. In a paper published in Vol. III. of these “ Proceedings,” 
(p. 409), I gave some investigations on the ratio between the forces 
tending to produce translation and rotation in the bores of rifled guns. 
2. My object in these investigations was to show—1st, that in the 
rifled guns with which experiments were then being made, the force 
required to give rotation was generally only a small fraction of that 
required to give translation; 2ndly, that in all cases (and this was a 
point about which much discussion had taken place), the increment of 
gaseous pressure (that is, the increase of bursting force) due to rifling 
was quite insignificant. 
3. In the paper referred to, although the formulae were sufficiently 
general to embrace the various systems of rifling then under con¬ 
sideration in England, they did not include the case of an increasing 
twist, which has since been adopted for the 8-in. and all larger guns of 
the British service; neither was our knowledge of the pressure of fired 
gunpowder sufficient to enable me to place absolute values on either of 
the forces I was considering. 
4. Since the date at which I wrote, an extensive series of experi¬ 
ments has been made in this country; and the results of these 
experiments enable me to give with very considerable accuracy both 
the pressure acting on the base of the projectile and the velocity at 
any point of the bore. I am therefore now able not only to assign 
absolute values where in my former paper I only gave ratios, but also to 
show the amount by which the studs of the projectiles of heavy guns 
have been relieved by the introduction of the accelerating twist known 
as the parabolic system of rifling. 
5. Very little consideration will satisfy anyone conversant with the 
subject, that in the ordinary uniform spiral or twist the pressure on the 
studs or other driving-surface is a maximum when the pressure on the 
