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Proof
The formal approval date of the "Cartridge S.A. Proof 15mm Q Mark I" is uncertain and it does not appear to have been shown in List of Changes. It was to Design DD/L/10005 dated April 1941 so approval would have been about that time.It utilised the bullet of the Ball Mark I round and weighed 1160 grains The case was copper washed ("reddened") although some examples seem to have been left in the plain brass state. The headstamp included the code "Q I" with a yellow primer annulus. Early production rounds are headstamped simply "Q" or "Q.I" without manufacturer or date.The exact charge varied, Kynoch records for Order Z6911 showing 282 grains of Cordite MDT 7-2 whilst Ordnance Board Proceedings 6530 indicate a charge of 265 grains of Cordite MDT 7-2. The specification called for the pressure developed to be 28 - 30 tsi.The Proof Q Mark I was shown as obsolescent in October 1946.Illustrated are (left) early proof round headstamped only "Q" and (right) Proof Q Mark I headstamped "K 40 QI".Tracer
"Cartridge S.A. Tracer 15mm G Mark Iz" was approved in August 1941 and shown in LoC Paragraph B.5434 dated December 1941. It was to Design DD/L/11161.The boattailed bullet was similar to the Ball Mark I with a gilding metal envelope over a mild steel core with a lead/antimony tip filler. Unlike the ball bullet, the steel core was drilled at the base to accept the tracer compound which was the same as the WG Mark Iz, 6 grains of SR368 with 6 grains of SR370 priming compound. The trace was to 800 yards.The charge was 360 grains of nitrocellulose to give a velocity at 90 feet of 2,900 feet per second at a maximun mean pressure of 22 tsi.The headstamp included the code "G.IZ" with a red primer annulus. Early production had a red tip and some had a red stripe across the case head.The Tracer G Mark Iz was shown as obsolescent in October 1946.Illustrated is an early tracer round with red tip and red case head stripe.
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