142 THE INFLUENCE OF AMMUNITION ON SHOOTING. 
the range were found with a cartridge made of one lot of powder and. 
the next round were fired with a cartridge of another lot, the gun 
might shoot entirely differently. Assuming that all the cartridges are 
of one lot, and, neglecting for the present items 2 and 8, it is clear 
that once the range is found the gun will continue to shoot to that 
range within the limits of error of its “probable rectangle.” The 
minor variations in muzzle velocity, due to variations in the powder, 
are part of the cause of errors in shooting which are summed in the 
term ‘probable rectangle.’ ‘The mean range corresponds to the mean 
muzzle velocity of the series. I wish to clearly distirguish between 
minor variations of muzzle velocity in rounds of the same lot and the 
variations between the mean muzzle velocity of rounds of different lots. 
The latter only will be considered in this paper, as being within the 
province of the battery officer to correct for. The former is for the 
consideration of the manufacturer. 
The range table for the 15-pr. B.L. gun is made out for a velocity of © 
1550 fis. Taking the specification limit of 40 f.s. there are lots in the 
service which may give a mean velocity of anything between 1570 f.s. 
and 1530 fis. The range table gives the elevation for 2000 yards with 
the Mark II. carriage as 3°12’. My calculations with the range 
table data give the range for 8° 12’ as 1994 yards. This isa sufficiently 
close result to justify my other calculations which are made ina similar 
manner to the ‘ test’ one. 
The following table shows the results assuming the three muzzle 
velocities of 1530, 1550 and 1570 f.s. In each case the gun is fired at 
an elevation of 3° 12’ and the range is on the horizontal plane passing 
through the resting points of the wheels. 
: : ; ini A ; 
Muzzle velocity. | Range. Yards. | Time of Flight. Saude ; eee 
1530 f.s. 1962 4915 secs. 940 fis. 4°602° 
1550 fis. 1994 4-991 secs. 947 f.3. 461° 
1570 fis. 2037 5:055 secs. 947 fis, 4 658° 
At the outset then we are face to face with the fact that, when 
shooting at the range table elevation for 2000 yards, it is possible with 
different lots to get a variation in range of 75 yards.' But if we con- 
tinue to use the same lot of powder for consecutive rounds it is 
immaterial which of these velocities the powder is giving. ‘The guns 
can be elevated so as to range correctly for the velocity at which they 
are shooting, and if they hit it matters not whether they are shooting 
to the range table or otherwise. ‘ale 
Before passing to the consideration of fuzes, it will be well to notice 
here another point in the above table. Column 1 on the range table 
gives the remaining velocity at any range, assuming a muzzle velocity 
of 1550 f.s. I find that the remaining velocities, so given, agree with 
aa 
1 This does not take into account the variations in velocity due to various ages, and conditions 
of different lots. 
