RIFLE CLUB AMMUNITION

Taranaki Daily News, 1 December 1932, Page 12

RIFLE CLUB AMMUNITION

ITS UNIFORMITY QUESTIONED

INVESTIGATIONS BY A RIFLEMAN.

SEARCHING INQUIRY CONDUCTED. (By J. Vinten, Secretary Hawera Defence Rifle Club.) In recent years the standard of rifle •hooting has been considerably below that obtained prior to the introduction of Mark VH ammunition. The scores -registered at the national meeting each year at Trentham since the compulsory use of Mark VH have been well below those attained by the use of Mark VI, and this would seem to indicate a deterioration in the quality of the new iMues of ammunition. This contention is apparently substantiated by the complaints made by riflemen concerning the uniformity and dependability of the ammunition. . The effects upon the rifle, of a bullet feeing discharged are several. The bullet on leaving the case in the breech fits tightly, and as nearly as possible reals the barrel, meeting a frictional resistance during its passage towards the muzzle. Any variation from shot to shot in size or weight of bullet will •fleet the resistance which it meets •rtd will therefore either diminish or increase its velocity. MOVEMENTS OF BARREL. The shock of discharge and the friction and movement of the bullet in the barrel produce certain movements of the barrel during the time that the bullet i« still in the rifle. The first of these, known as the “jump,” is a bodily movement of the barrel in its bedding, while the second, called the “flip,” is a bending of the barrel resulting in an upward or a downward movement of . the muzzle. The amount of the jump depends upon the size of the charge as well as upon the style of -the bedding. The flip iS also, governed by the size Of the charge, •nd is further affected by the weight of the bullet and the frictional resistance which it receives. With Mark VI ammunition the barrel first bends downwards, and is half-way back when the bullet leaves the muzzle from a normal charge. With Mark VII ammunition the muzzle is at the bottom of the downward flip when the bullet leaves. It is therefore evident that any variation in the weight and size of the projectile, or in the amount or rate of ignition of the charge, has a tendency to vary the velocity of the bullet and the position of the barrel when the bullet departs, thus considerably affecting elevation. Any of these variations will give an elongated diagram of shots upon a target, instead of the circular diagram with approximately 95 per cent, of the •hots in the centre, which occurs with uniform ammunition. Therefore, it is manifest that uniformity is essential in the weight and diameter of the base of the bullet and in the weight of the charge if consistent •hooting is to be obtained. With these ■ premises in view, I have examined various issues of ammunition. VARIATIONS MEASURED. In the above characteristics the ammunition of recent issues tends to bear •way from the necessities of a firstclass article.

I have examined the cartridges, bullate and charges of 10 packets, of Mark VII 1928 cordite chosen at random from • case. The diameters of the bullet base varied from 7.825 millimetres 9 to 7.925 millimetres. The following table •hows the variation in weight of bullet and charge in four examples selected for their varying diameter of bullet base: —

In a proved issue of ammunition such ag: Mark VI 1910 C.A.C. cordite the weight of the bullet varied no more than - from 13.89 grammes to 13.88 grammes and the weight of the charge (2.05 grammes) showed no variation. In Mark VH 1924 English cordite the weight of the bullet varied only from 11.31 to 11.30 grammes and the weight of the charge (2.28 grammes) showed no variation. These two issues of ammunition have been well proved and their capabilities for the making of good scores are well recognised. It is noticeable how constant the weights are in these two issues and .it points to the type of ammunition required for consistent shooting. In the manufacture of ammunition the case and the bullet are made separately after which the case is passed through a machine which fills it with the charge. This machine is stopped at short intervals and the case, plus the charge, .is weighed to check the amount of«charge being given. The bullet is then inserted, and packed ready for sale. Therefore the uniformity of the charge demands uniformity in weight of case, but from the tables below the weight is not uniform in recent issues:—

It is therefore probable that variations in the weight of the cartridge case are, in themselves, one of the sources of variation in the weight of charge. In many quarters there has been a suspicion that the velocity imparted to the Mark VII bullet is too great, and that a gyroscopic flight results. In consequence, grouping at short 'ranges is difficult, whereas at longer ranges the bullet has “settled down” in . flight and gives more consistent grouping. Support is lent to this view by the observation that English Mark VII cordite of proved consistency has not only a smaller charge, but also a heavier bullet than the more erratic C.A.C. issue. This comparison is made all the more significant by observing the still smaller charge and Still heavier bullet of the once famous 1910 Mark VI C.A.C. cartridge. More recent issues of ammunition appear to be of a higher standard, and riflemen throughout the Dominion would welcome a decision by the authorities to make these issues immediately available for target use, while reserving for less exacting military purposes the batches of ammunition whose defects have been revealed by this investigation. In conclusion I would like to thank Mr. P. O. Veale for the advice and assistance given and the Federation of Taranaki Co-operative Dairy Factories for the use of their scientific apparatus.

Diam. of base Weight of bullet Weight of chge. No. m.m. grms. • grms. 1 ...... 7.825 11.19 2.41 2 ..... 7.885 11.10 2.40 3 ...... 7.905 11.15 2.30 4 ..... ...... 7.925 11.41 2.36

C.A.C. 1924 Mark VII English 1924 1910 Mark VII Mark VI No. grms. grms. grms. 1 ...... 11.10 10.00 11.60 2 11.36 9.99 11.60 n* r - - - - ...... 11.62 , 9.98 11.62 4 11.71 •9.97 t 11.60