TABLE GIVING SOME OF SIR. A. NOBLE'S EXPERIMENTS. ________________________________________________________________________ | | | VELOCITIES OBTAINED. | |________________________________________________________________________| | | | | | | | | In a 40 | In a 50 | In a 75 | In a 100 | | | Cal. Gun.| Cal. Gun.| Cal. Gun.| Cal. Gun.| |____________________________|__________|__________|__________|__________| | | | | | | | |Foot Secs.|Foot Secs.|Foot Sees.|Foot Secs.| | | | | | | |With cordite 0.4 in. diam. | 2,794 | 2,940 | 3,166 | 3,286 | | " " 0.3 " | 2,469 | 2,619 | 2,811 | 2,905 | | " ballistite 0.3 in. cubes| 2,416 | 2,537 | 2,713 | 2,806 | | " French B.N. for | | | | | | 6-inch guns | 2,249 | 2,360 | 2,536 | 2,616 | | " prismatic amide | 2,218 | 2,342 | 2,511 | 2,574 | | | | | | | |____________________________|__________|__________|__________|__________| | | | ENERGIES REPRESENTED BY ABOVE VELOCITIES. | |________________________________________________________________________| | | | | | | | |Foot Tons.|Foot Tons.|Foot Tons.|Foot Tons.| | | | | | | | 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 | |____________________________|__________|__________|__________|__________|
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° F., and cordite M.D. 160° 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° F. the cordite used in the 4.7-inch gun is considerably affected as regards pressure.
Colonel Barker, R.A., in reply to a question raised by Colonel Trench, R.A. (at the Royal Artillery Institution), concerning the shooting qualities of cordite heated to a temperature of 110° F., said: "Heating cordite and firing it hot undoubtedly does disturb its shooting qualities, but as far as we can see, not much more than gunpowder. I fear that we must always expect abnormal results with heated propellants, either gunpowder or cordite; and when fired hot, the increase in pressure and velocities will depend upon the heat above the normal or average temperature at which firing takes place." Colonel Barker also, in referring to experiments that had been made in foreign climates, said: "Climatic trials have been carried out all over the world, and they have so far proved eminently satisfactory. The Arctic cold of the winter in Canada, with the temperature below zero, and the tropical sun of India, have as yet failed to shake the stability of the composition, or abnormally injure its shooting qualities." Dr Anderson is of opinion that cordite should not be stored in naval magazines near to the boilers. Professor Vivian B. Lewes, in his recent Cantor Lectures before the Society of Arts, suggests that the magazines of warships should be water- jacketed, and maintained at a temperature that does not rise above 100° F.
~Axite.~—This powder is manufactured by Messrs Kynock Limited, at their works at Witton, Birmingham. The main constituents of cordite are retained although the proportions are altered; ingredients are added which impart properties not possessed by cordite, and the methods of its manufacture have been modified. The form has also been altered. Axite is made in the form of a ribbon, the cross section being similar in shape to a double- headed rail. It is claimed for this powder, that it does not corrode the barrel in the way cordite does, that with equal pressure it gives greatly increased velocity, and therefore flatter trajectory. That the effect of temperature on the pressure and velocity with axite is only half that with cordite. That the maximum flame temperature of axite is considerably less than that of cordite, and the erosive effect is therefore considerably less. That the deposit left in the barrel after firing axite cartridges reduces the friction between the bullet and the barrel. It is therefore practicable to use axite cartridges giving higher velocities than can be employed with cordite, as with such velocities the latter would nickel the barrel by excessive friction. It is also claimed that the accuracy is greatly increased. The following results have been obtained with this same time, and under the same conditions:—
~Axite~ Cartridges with 200-grain bullets.
Velocity 2,726 F.S.
Pressure 20.95 tons.
~Axite~ Cartridges with 215-grain bullets.
Velocity 2,498 F.S.
Pressure 19.24 tons.