|Metric (mm)||Imperial (in)|
|Calibre||12.7 x 81||.5|
|Case Type:||Rimless, bottlenecked|
|Also known as:||
In British and Commonwealth service, the variants used are those shown in the Table below.
|Type||Mark||Charge||Bullet||Notes and acceptance tests||Identification|
|Ball||1z||Cupro-nickel envelope, lead/antimony core and aluminium tip. Two cannelures. Secured by coning into forward cannelure and indenting into rearward.||Obsolescent [As of 1945 publication]. Rimless case. Figures “469” on base.||Purple annulus.|
|2||142.5gr. Cordite 7/2||Weight 580gr. Coated steel envelope, lead/antimony core and aluminium tip. Slightly longer than Mk. 1.||Mk. 2 obsolescent [As of 1945 publication]. Accuracy: 9-in. F. of M. at 500 yards.||Purple annulus.|
|2z||140gr. N.C.||Purple annulus.|
|Armour Piercing||W.1||142gr. Cordite 7/2||Weight 580gr. Steel envelope coated with cupro-nickel, combined tip and sleeve of lead/antimony and hard steel core.||Before 1934, “W” was omitted from base stampings. Accuracy: 12-in. F. of M. at 500 yards. Penetration: 70 per cent., 18mm. Armour Plate at 100 yards.||Green annulus.|
|W.1z||140gr. N.C.||Green annulus.|
|Semi-Armour Piercing||F.1||142gr. Cordite 7/2||Weight 580gr. Coated steel envelope, lead/antimony sleeve and steel core.||Accuracy: 12-in. F. of M. at 500 yards. Penetration: 70 per cent., 15 mm. Armour Plate at 100 yards.||Green annulus.|
|F.1z||140gr. N.C.||Green annulus.|
|S.A.P./Tracer||F.G.1z||140gr. N.C.||Weight 542gr. Similar to F. Mk. 1, except that core is recessed to take 6 gr. S.R.368 (tracing) and 6 gr. S.R.370 (priming). Base closed by brass washer with envelope turned over on to it.||Accuracy: 12-in. F. of M. at 500 yards. Penetation: 70 per cent., 15 mm. Armour Plate at 100 yards. Tracing: 85 per cent. must trace to 100 yards.|
|F.G.2z||140gr. N.C.||Weight 549gr. No information re make-up of filling.||Accuracy: As for F.G.1z. Penetration: As for F.G.1z. Tracing: Dark Ignition, 85 per cent. must trace to 800 yards after 100 ± 40 yards.|
|Incendiary||B.1z||142gr. N.C.||Weight 562gr. Make-up similar to .303 B, Mk. 7. Filling 28gr. S.R.365 and 2gr. Q.F. composition.||Accuracy: 18-in. F. of M. at 500 yards. Performance: 17/20 good flashes on impact.||Blue annulus.|
|Proof||Q.1||140gr. Cordite 3½||Ball 1z Bullet. Weight 580gr.||Cartridge coppered all over. Gives pressure of 17/29 tons per sq.in.||Yellow annulus.|
|Dummy||U.1||Nil||Weight 590gr. Copper alloy or coated steel envelope with lead/antimony core and aluminium tip.||Non-explosive. Wooden distance piece under bullet. Chromium-plated brass, or white metal case.|
|Drill||D.1||Nil||Weight 370gr. Cupro-nickel envelope and aluminium core.||Non-explosive. Wooden distance piece. Case of chromium-plated brass with 3 longitudinal grooves in body. Empty cap chamber.|
Countries using this calibre
The ball variant of this calibre appears to have been largely used for training purposes as it was ineffective against any form of armour, and that was the purpose of the .5-inch Vickers Mk V at the start of the Second World War in the light tanks. Whilst war establishments and mobilization tables set out the amount of ammunition to be held in readiness by units, it was necessary to allocate training ammunition on a year-by-year basis for the weapon training year. In 1939 this was identified in Army Council Instruction 381:
- Each cavalry armoured car and light tank regt., R.A.C.: 60 rounds for each trained soldier.
- Each bn. R.T.R.: 60 rounds for each trained soldier.
- A.F.V. School – Gunnery Wing: 25 rounds for each recruit; 200 to school for demonstration purposes.
- For students, etc.: 17,400 rounds.
This then allowed the men to fire the practices from Tank Training, Volume II, Part II, 1936.