THE ROYAL ARTILLERY INSTITUTION. 
259 
How far, then, is it probable that the gun and carriage, weighing 
together 2664 lb., would have recoiled in the one-hundredth part of a 
second ? Is it likely that the difference in quickness of recoil—even if 
such existed—between the 3‘3-in. and 3*6-in. guns would in this time 
have had the smallest appreciable effect on the angle of departure of 
the projectile ? 
During the trial of the 3*3-in. and 3'6-in. guns, the recoil was 
“ checked ” by means of sand-bags placed six feet in rear of the wheels . 
The recoil was unchecked up to the sand-bags. Under these circum¬ 
stances, is it possible that the checking could have had the slightest 
effect whatever ? Would not the shell have been out of the muzzle, 
either at 2°, 5°, or 10° elevation, long before the gun had recoiled 6 ft. ? 
Let me not be misunderstood. I am not here arguing that the angle 
of projection is unaffected by the reaction of gun and carriage. It is 
a well-known fact that the apparent elevation of a gun is increased by 
an—as it were—involuntary movement of the system on the discharge of 
the piece.* This motion, or tendency which the gun and carriage have to 
rotate on the trail, is however quite distinct from any backward motion 
of the wheels. Experiment has shown that this “jump” which the 
system makes before the projectile leaves the muzzle is much affected by 
the nature of the rifling. A breech-loading gun in which the shot is 
forced through the bore, “jumps” more than a muzzle-loading gun 
of the same weight and length. 
There have been several experiments made, from time to time, with 
a view of ascertaining the value of the “jump” with different guns, 
and the results, on the whole, show that [cceteris paribus) the preponder¬ 
ance of a gun, or the method in which the breech is attached to the 
elevating arrangement has no appreciable effect.f 
Now, the difference in preponderance between the 3'3-in. and 3'6-in. 
guns was only lib. Both guns were fired off the same carriage and 
same nature of ground. I think, therefore, that, looking to the above 
facts, it is exceedingly improbable that the 3'6-in. gun threw higher 
than the 3'3-in.; and that in the absence of some more satisfactory 
reason than the one alleged, it is only fair to assume that the observed 
ranges are correct, and the calculated ranges incorrect. 
The following table gives the results of some trials to ascertain the 
“jump ” of various guns. 
The method usually followed at Shoeburyness in carrying on such 
experiments, is this :— 
A wooden target, 9 ft. square, is erected at 120 ft. from the gun. 
The axis of bore of the latter is truly levelled by a quadrant, so 
as to be horizontal. The corresponding height of this level is then 
found on the target by a theodolite. The gun is then fired, and 
the position of the hits on the target determines the amount or 
value of the “jump.” It is evident that if there were no “jump,” the 
* See “ Second Report on Ballistics,” bj Captain W. H. Noble, R.A. 1865, p. 268. 
f See “ Report of Special Committee on Eield Artillery Equipment for India.” 1869, p. 25. 
The results of these experiments have recently been corroborated by similar trials in France. 
