That is a post card, let me see if I can found it..again.
25,4mm antiaircraft guns in "La Argentina Class"
by Tony Williams:
This article is a compilation of material published in the May and June issues of 'The Cartridge Researcher', the Bulletin of the European Cartridge Research Association
I recently came across description of the Argentinian light cruiser 'La Argentina', which was built between 1936 and 1939 by Vickers of Barrow. A brief mention was made that the ship was armed with one-inch Vickers AA guns. I was puzzled by this, as the only Vickers one-inch guns I knew were produced during WW1 and were low-velocity aircraft weapons which would have been of little use in the AA role by the 1930s. So I made some enquiries via the ECRA network, and details of an almost forgotten weapon gradually emerged.
The Gun
The gun is referred to as the 'Vickers 25.4 mm', presumably to distinguish it from the earlier Vickers 1 inch. It appears to have been developed in the early to mid-1930s specifically as a naval gun, and was only ever produced in a fixed twin mounting. I am unaware of any other application of this gun apart from 'La Argentina', which had six of these mountings. One gun (without mounting) still survives in the MoD Pattern Room at Leeds. The mountings were removed from 'La Argentina' in 1949 and replaced by six single 40mm Bofors mountings. None of the mountings appears to have survived, although there is a mystery concerning the ammunition production dates which will be referred to later.
A low-resolution photo of the mounting is included (below left), from the Barrow Museum in Cumbria, which contains much material concerning Vickers (for a long time the town's biggest employer).
They have six different high-resolution photos of this mounting available for purchase as photographic prints: they may be viewed on-line and ordered from:
Vickers Photographic Archive (enter 25.4mm in the 'search' box).
The photo of the cruiser was kindly supplied by A.A.C.A.M. (see credits at the end of the article) and shows two of the 25.4 mm twin mountings, barrels pointing skywards; one on each side of the bridge, under the bridge overhang. The entire starboard mounting can be seen, but only the barrels of the port mounting. The photo of the gun is courtesy of the MoD Pattern Room.
The guns look very different from the traditional Vickers large-calibre automatic guns of the period, which were belt-fed, water-cooled and recoil-operated. They are obviously air-cooled, almost certainly gas-operated, and are fed by box magazines above the breech. Since Vickers was offering the gas-operated, magazine-fed Vickers-Berthier .303 LMG at that time (it was used by the Indian Army instead of the Bren), and the Vickers K or VGO aircraft gun derived from it, it seems reasonable to theorise that the 25.4 mm gun used a scaled-up version of this mechanism. No information has been found concerning the the mounting, the magazine capacity, or the rate of fire. However, some rounds of ammunition have survived.
The Ammunition
The cartridge for the 25.4mm gun is a slender, rimless, bottleneck type with a case length of 189mm. Two different types of projectile are known; an APC (loaded into the cartridge examined) and an HE shell for which information and illustrations have been provided by A.A.C.A.M.
The APC projectile (below centre) is painted black apart from the copper driving band and weighs 250g. The nose-fuzed HE projectile (below left) is in worse condition, but retains traces of red paint. According to an official drawing, it weighs 260g.
In the Projectiles and Grenades Catalogue of the Ammunition and War Chemistry Commission (Navy Material General Directorate), A.A.C.A.M. have found a blueprint of the HE projectile (shown below) and comment as follows:
"In the A.A.C.A.M. own reference collection, we have: one cartridge that was obtained from a retired navy non commissioned officer, who worked in the naval museum, and as he told us, some years ago he got some cartridges from crates of ammunition that were to be dumped at sea. It bears the headstamp: VA AR (Argentine marking that means "ARMADA" – navy -) 1938 LOT 8 25.4 M/M. Markings were at 12-3-6 and 9 position. The projectile bears in the fuze the marking: L10 1939, and in the body 25.4 M/M VAD 1939. The projectile has traces of red paint, we presume this is the original paint.
The explosive seems to be Trotyl, because the denomination found in this blueprint A.E.A.T. means: GranadA Explosiva Antiaerea Trotyl.
According to the blueprint 3.8 % of the projectile weight (without fuze) is explosive material.
Also, one case was obtained from the "Fray Luis Beltran" ammunition factory. Unconfirmed reports said that was there for fatigue material testing, it bears the headstamp VA AR 1938 LOT 3 25.4 M/M, and most interesting is the primer (Argentine made) with the following markings: A.A.M.Z. /57 PP-21, meaning that it was made by the Arsenal Artilleria de Marina Zarate (Zarate Navy Artillery Arsenal) probably in 1957. Our speculation is that once the supply of British made ammunition was exhausted, the navy maybe tried to reload it with Argentine-made components. Whether other components (beside primers) i.e. projectiles, were made in Argentina is still matter of investigation.
This fact is very interesting, because if the MGs were replaced in 1949, and in the year 1957, A.A.M.Z. was making primers, this means that somebody was still using the MGs: who, where and when is still a mystery to us.
The AR marking denotes Argentine navy property."
The following information concerns an example of the cartridge with an APC projectile, which was examined in detail.
The cartridge case is brass, with a dark coating or patina, the primer also brass but much brighter.
The dimensions of the cartridge in millimetres are as follows:
Lengths:
· Case: 189
· To shoulder: 164
· Neck: 18
· Rim: 2.5
· Extractor groove: 2 (level) + 3 (angled)
Widths:
· Rim: 34.8
· Extractor groove 32.3
· Body above extractor groove: 34.3
· Body at shoulder 30.3
· Body at neck: 26.0
· Primer diameter: 20.2
APC Projectile
· Length visible above case: 68.0
· Overall length: 86.0
· Length of driving band: 10.0
· Diameter of driving band: 26.0
· Diameter of projectile body: 25.3
Weights:
· Overall: 560 g
· Projectile: 250 g
Headstamp: 25.4m/m VA 1936 LOT
Primer: No.5 IIN (WD arrow in diamond) VAD 11/35 VAD
Projectile: VAD 25.4m/m P. 25443 GL
Other sources
No official statistics have been found concerning the muzzle velocity or range of the cartridge. However, in "Spitfire, the History" by Morgan and Shacklady (Key Publishing Ltd, 1987) there is on page 61 a table of alternative armaments proposed for the Spitfire during its design/development phase. Included in these (rather surprisingly) is the 25.4mm Vickers. This is credited with a shell weight of .551 lbs (250 g) which is accurate for the AP projectile, and a muzzle velocity of 3,000 fps (914 m/s), which looks about right given the size of the cartridge case. This develops a muzzle energy of 104,400 J; it is probable that the same round-figure muzzle velocity would have been quoted for the HE shell, giving an energy of 108,600 J.
This source also credits the gun with using a 30-round drum, but that may have been specifically for the aircraft application where reloading would not have been possible. The book gives a gun weight of 127 kg and a length of 259 cm.
What does not look right in the Morgan/Shacklady book is the quoted "weight of shells per minute (max lbs)" which is given as 55 lb (25 kg). This is only equivalent to 100 rpm, which appears far too low given that the contemporary Bofors 25mm fired at 160-180 rpm and the 25mm Hotchkiss at 200-250 rpm.
Acknowledgements
Thanks are due to the Vickers Museum, Barrow, to Martin Golland, for the loan of his 25.4 mm cartridge for measurement and photography, to Richard Jones of the Pattern Room, to Bill Woodin of the Woodin Laboratory, and to members of the Argentinian cartridge collectors' association (A.A.C.A.M.) for providing much of the material, as follows:
Dr. Horacio A. Tomas (A.A.C.A.M. current President)
Rear Admiral Oscar C. Albino (A.A.C.A.M. former President)
Mr. Federio Graziano (A.A.C.A.M. voting member, and a true authority in the ammunitions field)
Mr. Osvaldo Bonsignori (A.A.C.A.M. Librarian)
Dr. Javier M. Ramallo (A.A.C.A.M. voting member)
THE VICKERS 25