| | | | | | | Cordite 0.4 inch | 5,413 | 5,994 | 6,950 | 7,478 | | Ballistite 0.3 inch cubes | 4,227 | 4,754 | 5,479 | 5,852 | | French B.N. | 4,047 | 4,463 | 5,104 | 5,460 | | Prismatic amide | 3,507 | 3,862 | 4.460 | 4,745 | |____________________________|__________|__________|________
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And again, in speaking of his own experiments, he says:  “One 4.7-inch gun has fired 1,219 rounds, and another 953, all with full charges of cordite, while a 6-inch gun has fired 588 rounds with full charges, of which 355 were cordite.  In the whole of these guns, so far as I can judge, the erosion is certainly not greater than with ordinary powder, and differs from it remarkably in appearance.  With ordinary powder a gun, when much eroded, is deeply furrowed (these furrows having a great tendency to develop into cracks), and presents much the appearance in miniature of a very roughly ploughed field.  With cordite, on the contrary, the surface appears to be pretty smoothly swept away, while the length of the surface eroded is considerably less.”

[Illustration:  FIG. 39.—­COMPARATIVE PRESSURE CURVES OF CORDITE AND BLACK POWDER. a, Charge, 48 lbs. powder; b, charge, 13 lbs. 4 oz. cordite; c, charge, 13 lbs. 4 oz. powder.  Weight of projectile, 100 lbs. in 6-inch gun.  M.V.  Cordite = 1960 feet seconds.]

The pressures given by cordite compared with those given by black powder in the 6-inch gun will be seen upon reference to Fig. 39, which is taken from Professor V.B.  Lewes’s paper, read before the Society of Arts; and due to Dr W. Anderson, F.R.S., the Director-General of Ordnance Factories.

It has been found that the erosive effect is in direct proportion to the nitro-glycerine present.  The cordite M.D., which contains only 30 per cent. nitro-glycerine, gives only about half the erosive effect of the old service cordite.  With regard to the heating effect of cordite and cordite M.D. on a rifle, Mr T.W.  Jones made some experiments.  He fired fifty rounds of .303 cartridges in fifteen minutes in the service rifle.  Cordite raised the temperature of the rifle 270 deg.  F., and cordite M.D. 160 deg.  F. only.

With regard to the effect of heat upon cordite, there is some difference of opinion.  Dr W. Anderson, F.R.S., says that there is no doubt that the effect of heat upon cordite is greater than upon black powder.  At a temperature of 110 deg.  F. the cordite used in the 4.7-inch gun is considerably affected as regards pressure.