THE ROYAL ARTILLERY INSTITUTION. 
203 
After each series of 200 rounds the bore was carefully examined and 
its dimensions taken. At the termination of the first 200, the bore 
about the middle of its length had expanded very slightly (0"*036 about) 
whilst a few small flaws (from tin spots), of lenticular shape, had been 
developed in the powder chamber and at the commencement of the 
rifling. These flaws slightly increased up to 300 th round, but from 
that to the 2000 th they remained constant both in number and size. 
The diameter of the powder chamber remained nearly the same, for 
though measurement showed an enlargement of (0*l m - m *) 0.0039 inches; 
this was due merely to the depth of a flaw and not to a real expansion of 
the chamber.* 
The committee carrying on these trials also tested a steel 8*7c B.L. 
gun of the same construction under similar conditions, and the follow¬ 
ing is a brief summary of their provisional report rendered in January, 
1875, when 2147 rounds had been fired from the bronze steel, and 1196 
from the steel gun. 
1. “The bronze steel gun shows sufficient ‘ resistance ’ (as to hard¬ 
ness, tensile strength, &c.), since after 2147 rounds with service 
charges the bore shows no degradation of form while the increase in 
diameter is within admissable limits.” 
2. “The experiments prove that in accuracy of fire the bronze steel 
equals the steel gun. The doubts expressed prior to trial as to the 
inability of bronze, even when treated by the Uchatius process, to 
withstand the action of the gas at a high temperature without erosion 
were not without foundation. The erosions caused do not however seem 
to affect the accuracy of fire as was expected.” 
“At the 2121st round the committee caused a shell to be exploded 
in the bore of the bronze steel gun, by which almost all the lands were 
more or less injured. Notwithstanding this damage and the erosions 
caused by much fire, the accuracy of the piece was not diminished, and 
the committee do not, therefore, consider such erosions of much 
importance, unless occurring in the neighbourhood of the gas check in 
the breech-end of the powder-chamber. Tin spots in that part of the 
gun are readily discovered, and it is recommended that any gun showing 
such should be rejected.” 
“The committee believe that the remarkable results obtained in 
these experiments are due partly to the Uchatius mode of constructing 
bronze guns, and partly to the use of copper rings for giving rotation 
to the projectiles.” 
Since the date of this report the committee have resumed their 
experiments, and 800 rounds more have been fired from the bronze 
steel gun mentioned, making a total of 2947 without material injury to 
the piece. Ten other guns have been constructed of the same material, 
from two of which 1500 rounds a-piece have been fired without their 
being injured in the slightest degree (according to Austrian news¬ 
papers) . 
# The mean expansions of chamber after firing above 2000 rounds, were steel gun 17 , 
bronze steel 14 in lOOOths of a millimetre. 
27 
