Another recent addition that I thought may be of interest.
Information below is taken from "British Small Arms Ammunition 1864-1938 by P. Labbett".
"In November 1933 the Director of Naval Ordnance outlined the need for a new multiple machine gun to be of a calibre intermediate between that of the .5 inch Vickers and the 2 pdr Pom Pom. Since these were anti aircraft weapons, it was stated that the time of flight of the bullet to a range of 2000 yards was of the greatest importance, a short time being required.
Shortly afterwards the outline design criteria for the ammunition was decided and although at one time a calibre of .75 inch was considered as well as .661 inch, the latter was finally selected, the bullet weight to be 3 ounces (1313 grains), with a working pressure of 25 tons per square inch. A muzzle velocity of 3000 feet per second was required.
In the first instance one six barrelled equipment was scheduled for delivery in August 1937, this being part of a development order for six such equipments. Until a gun was available development of suitable ammunition would take place with a number of .661 pressure barrels. The guns themselves were made by Vickers Armstrong Ltd. What Vickers Armstrong were never told was that the .661 gun was very seriously considered as a system to be fitted with cone chamber barrels and to fire Gerlich-type bullets. In a Gerlich mode the emergent calibre was intended to be .52 inch and, with a case capacity of about 3 cubic inches a muzzle velocity of about 5000 feet per second with a 570 grain bullet was envisaged.
In March 1936 in view of the slowness of the cone chamber development, the DNO decided that the .661 inch multiple equipment would follow conventional lines, i.e. the lines communicated to Vickers Armstrong and that when the experiments with the Gerlich programme being carried out at Woolwich bore fruit, the results then could be incorporated later.
In May 1936 ICI Ltd supplied 1000 .661 cases to design DD/L/7333 together with 500 AP bullets to DD/L/6614 and 500 ball bullets to design DD/L/7435. The AP bullet had a carbon steel core. At this stage the propellant used was Cordite MDT.
The .661 inch brass cartridge case was semi-rimless and bottlenecked, with a length of 149mm. Rim diameter was 29.1mm and head diameter 26.6mm. The case was Berban-primed and overall cartridge length was 190mm.
At one stage in 1838 consideration was given to using cadmium coated steel cases instead of brass, but nothing came of this.
In January 1937 firing trials with the .661 inch ammunition fired from a pressure barrel were held against parked aircraft including aircraft with the engine running. These trials demonstrated to the trial organisers that solid bullets could no longer be relied upon to stop an aircraft engine even in the engine was hit. It became clear that the bullets incorporating an explosive content would be required.
In March 1937 two further designs of .661 inch ball and AP bullets were produced, covered by designs NOD 3883 and NOD 3882 respectively. Each weighing 1310 grains.
At about the same time Vickers Armstrong Ltd submitted two HE bullet designs each with a base fuze mechanism. These were:-
Design 26101. GL Having a hard steel head with a 6CRH ogive, the bullet weighed 2.5 ounces, including a bursting charge of 56.5 grains of HE.
Design 26102. GL Having a hard steel head with 4.5 CRH ogive, the bullet weighing 2 ounces, including a bursting charge of 76 grains.
Later in 1937 the Research Department at Woolwich submitted a .661 inch base-fuzed incendiary bullet based on the .5 inch Vickers bullet to design RD 5132. The .661 inch version covered by design RD 5194.A was made from copper coated steel bar and this bullet was made in two versions, one filled with CE alone and the other with a mixture of CE and incendiary composition, the later being identified by a red band painted around the bullet. Later in 1938 a further base design fuzed design, RD 5271 was produced.
Whereas cordite had originally been the propellant used, necking the .661 inch case had presented annealing problems and to overcome these and to allow propellant more easily to be filled after case annealing nitrocellulose was introduced into the trials. Ammunition delivered by ICI Ltd in July 1937 was NC loaded the charge weight being 680 grains. With this charge muzzle velocities were obtained of 3287 feet per second with the AP bullet and 3312 feet per second with ball.
The nomenclature for .661 ammunition was finally fixed by the Admiralty as:-
“Cartridge SA Ball .661 inch Mark I.z (N)” (Bullet NOD 3883)
“Cartridge SA Armour Piercing .661 inch W Mark I.z (N)” (Bullet NOD 3882)
Prior to this the same nomenclature had been used with cordite ammunition but without the suffix letter “Z”. In spite of being awarded service nomenclature the ammunition was never adopted for service.
By February 1938 one complete gun had been delivered and was undergoing firing trials. However trained horizontally the achieved rate of fire with this gun was only 260 rpm and this would have fallen slightly with the gun elevated. At this stage some thought was given to an alternative barrel to be fitted to this gun chambered for a .8 inch (20mm) cartridge but nothing further seems to have been done to follow this up.
In September 1938 the Director of Naval Ordnance announced that the .661 project no longer met a Naval requirement and the project was cancelled. Five of the six equipments on order were cancelled and only the one actually delivered was to be retained for any future possible experimentation.
In fact in 1942 the .661 had a slight reprieve and in that year a pressure barrel in that calibre was used for high velocity work against armour plate. In the 1942 trials two types of .661 bullet were used both with Cordite MDT 9-2 as under:-
AP steel, solid shot with copper deposit on bearing surfaces, the bullet weighted only 710 grains and having a 1 CRH ogive
Two piece AP steel bullet with copper deposit on bearing surface weighing 660 grains and having a 2 CRH ogive.
With these light bullets muzzle velocities of about 4500 feet per second were obtained at 30 tons per square inch pressure, accuracy and penetration however being poor."
All INERT etc.
Dave.
Information below is taken from "British Small Arms Ammunition 1864-1938 by P. Labbett".
"In November 1933 the Director of Naval Ordnance outlined the need for a new multiple machine gun to be of a calibre intermediate between that of the .5 inch Vickers and the 2 pdr Pom Pom. Since these were anti aircraft weapons, it was stated that the time of flight of the bullet to a range of 2000 yards was of the greatest importance, a short time being required.
Shortly afterwards the outline design criteria for the ammunition was decided and although at one time a calibre of .75 inch was considered as well as .661 inch, the latter was finally selected, the bullet weight to be 3 ounces (1313 grains), with a working pressure of 25 tons per square inch. A muzzle velocity of 3000 feet per second was required.
In the first instance one six barrelled equipment was scheduled for delivery in August 1937, this being part of a development order for six such equipments. Until a gun was available development of suitable ammunition would take place with a number of .661 pressure barrels. The guns themselves were made by Vickers Armstrong Ltd. What Vickers Armstrong were never told was that the .661 gun was very seriously considered as a system to be fitted with cone chamber barrels and to fire Gerlich-type bullets. In a Gerlich mode the emergent calibre was intended to be .52 inch and, with a case capacity of about 3 cubic inches a muzzle velocity of about 5000 feet per second with a 570 grain bullet was envisaged.
In March 1936 in view of the slowness of the cone chamber development, the DNO decided that the .661 inch multiple equipment would follow conventional lines, i.e. the lines communicated to Vickers Armstrong and that when the experiments with the Gerlich programme being carried out at Woolwich bore fruit, the results then could be incorporated later.
In May 1936 ICI Ltd supplied 1000 .661 cases to design DD/L/7333 together with 500 AP bullets to DD/L/6614 and 500 ball bullets to design DD/L/7435. The AP bullet had a carbon steel core. At this stage the propellant used was Cordite MDT.
The .661 inch brass cartridge case was semi-rimless and bottlenecked, with a length of 149mm. Rim diameter was 29.1mm and head diameter 26.6mm. The case was Berban-primed and overall cartridge length was 190mm.
At one stage in 1838 consideration was given to using cadmium coated steel cases instead of brass, but nothing came of this.
In January 1937 firing trials with the .661 inch ammunition fired from a pressure barrel were held against parked aircraft including aircraft with the engine running. These trials demonstrated to the trial organisers that solid bullets could no longer be relied upon to stop an aircraft engine even in the engine was hit. It became clear that the bullets incorporating an explosive content would be required.
In March 1937 two further designs of .661 inch ball and AP bullets were produced, covered by designs NOD 3883 and NOD 3882 respectively. Each weighing 1310 grains.
At about the same time Vickers Armstrong Ltd submitted two HE bullet designs each with a base fuze mechanism. These were:-
Design 26101. GL Having a hard steel head with a 6CRH ogive, the bullet weighed 2.5 ounces, including a bursting charge of 56.5 grains of HE.
Design 26102. GL Having a hard steel head with 4.5 CRH ogive, the bullet weighing 2 ounces, including a bursting charge of 76 grains.
Later in 1937 the Research Department at Woolwich submitted a .661 inch base-fuzed incendiary bullet based on the .5 inch Vickers bullet to design RD 5132. The .661 inch version covered by design RD 5194.A was made from copper coated steel bar and this bullet was made in two versions, one filled with CE alone and the other with a mixture of CE and incendiary composition, the later being identified by a red band painted around the bullet. Later in 1938 a further base design fuzed design, RD 5271 was produced.
Whereas cordite had originally been the propellant used, necking the .661 inch case had presented annealing problems and to overcome these and to allow propellant more easily to be filled after case annealing nitrocellulose was introduced into the trials. Ammunition delivered by ICI Ltd in July 1937 was NC loaded the charge weight being 680 grains. With this charge muzzle velocities were obtained of 3287 feet per second with the AP bullet and 3312 feet per second with ball.
The nomenclature for .661 ammunition was finally fixed by the Admiralty as:-
“Cartridge SA Ball .661 inch Mark I.z (N)” (Bullet NOD 3883)
“Cartridge SA Armour Piercing .661 inch W Mark I.z (N)” (Bullet NOD 3882)
Prior to this the same nomenclature had been used with cordite ammunition but without the suffix letter “Z”. In spite of being awarded service nomenclature the ammunition was never adopted for service.
By February 1938 one complete gun had been delivered and was undergoing firing trials. However trained horizontally the achieved rate of fire with this gun was only 260 rpm and this would have fallen slightly with the gun elevated. At this stage some thought was given to an alternative barrel to be fitted to this gun chambered for a .8 inch (20mm) cartridge but nothing further seems to have been done to follow this up.
In September 1938 the Director of Naval Ordnance announced that the .661 project no longer met a Naval requirement and the project was cancelled. Five of the six equipments on order were cancelled and only the one actually delivered was to be retained for any future possible experimentation.
In fact in 1942 the .661 had a slight reprieve and in that year a pressure barrel in that calibre was used for high velocity work against armour plate. In the 1942 trials two types of .661 bullet were used both with Cordite MDT 9-2 as under:-
AP steel, solid shot with copper deposit on bearing surfaces, the bullet weighted only 710 grains and having a 1 CRH ogive
Two piece AP steel bullet with copper deposit on bearing surface weighing 660 grains and having a 2 CRH ogive.
With these light bullets muzzle velocities of about 4500 feet per second were obtained at 30 tons per square inch pressure, accuracy and penetration however being poor."
All INERT etc.
Dave.
