Cutaway model of a 17 pounder APDS-T cartridge. For comparison, the 6 pounder APDS-T has been placed beside it, so the difference in scale between both cartridges can be observed.
The 17 pounder QF anti-tank gun is the follow up of the 6 pounder anti-tank gun, that was in fact already near obsolete when entering service. Especially when taking into account the appearance of heavily armoured German tanks like the PzkW.V (Panther) and the PzkW.VI (Tiger 1) which were practically invulnerable for the 6 pounder APCBC-T armour piercing projectiles when encountering frontal armour. Remind that APDS-T shots for the 6 pounder were only available just after the Normandy landings.
Therefore, the design of the 17 pounder had already started in 1941, and it was brought in service with such speed, that by lack of carriage design it was mounted on a 25 pounder carriage. They were called 17/25 pounders and named “Pheasent”.
Only with later models the split tail carriage design was used.
The 17 pounder was also used in the Sherman firefly tank, and the Archer self-propelled anti-tank gun.
Both projectiles work according to the same principle: A base plate with gas check flanges houses a streamlined projectile. This projectile consists of a tungsten carbide core surrounded by an aluminium top body, and a steel lower body (with tracer element), roll crimped together. Around this complete projectile (seated in the base plate) an aluminium alloy sabot is placed, screwed over the outer thread of the base plate. In this sabot, three longitudal slots at 120 degrees each are machined, leaving just a small (quite weak) connection in top of the sabot. At the base of the sabot a radial groove is machined, leaving a small weak radial rim. Upon firing, the lands and grooves give the projectile rotation upon leaving the barrel. The centrifugal force breaks the sabot apart in three pieces over the three weakenings, throwing the sabots away sideways. The base plate catches the air stream and reduces in speed, separating from the streamlined projectile.
Due to the great reduction in cross section of the projectile it will have reduced drag which results in retaining great speed over longer distances, and a flat trajectory
Upon impact, the tungsten carbide penetrator will pass through the armour, causing spalling of red hot pieces of armour inside the enemy tank, as well as red hot –pieces of- the penetrator bouncing through the inside of the tank with high speed, igniting fuel and ammunition, either killing the crew.
The shellcase is brass made and measures 76,2 x 583R.
The Tungsten carbide penetrator weighs 1737 grams (1,73 Kg), it has a diameter of 38mm and a total length of 126,8mm.
The 17 pounder APDS-T projectile has a Vo. of 1200 mtrs/sec (3950 ft/sec) and could pierce a 204mm thick steel plate @30 degrees at 500 mtrs, and 185mm at 1000 mtrs.
The 17 pounder APDS-T was therefore able to knock out every German tank from every angle up to 1000 mtrs.
The 6 pounder APDS-T has a Vo. of 1234m/s (4050 ft/sec) and could pierce a 146 mm thick steel plate @30 degr at 1000 yards.
6 pounder posting:
http://www.wk2ammo.com/showthread.php?1137-6Pdr-(57x441R)-HE-(2x)-AP(3x)-APDS&highlight=apds
17/25 pounder “Pheasant”, #2:
http://www.bocn.co.uk/vbforum/threads/92195-17-Pounder-Drill?highlight=pounder
Regards, DJH
The 17 pounder QF anti-tank gun is the follow up of the 6 pounder anti-tank gun, that was in fact already near obsolete when entering service. Especially when taking into account the appearance of heavily armoured German tanks like the PzkW.V (Panther) and the PzkW.VI (Tiger 1) which were practically invulnerable for the 6 pounder APCBC-T armour piercing projectiles when encountering frontal armour. Remind that APDS-T shots for the 6 pounder were only available just after the Normandy landings.
Therefore, the design of the 17 pounder had already started in 1941, and it was brought in service with such speed, that by lack of carriage design it was mounted on a 25 pounder carriage. They were called 17/25 pounders and named “Pheasent”.
Only with later models the split tail carriage design was used.
The 17 pounder was also used in the Sherman firefly tank, and the Archer self-propelled anti-tank gun.
Both projectiles work according to the same principle: A base plate with gas check flanges houses a streamlined projectile. This projectile consists of a tungsten carbide core surrounded by an aluminium top body, and a steel lower body (with tracer element), roll crimped together. Around this complete projectile (seated in the base plate) an aluminium alloy sabot is placed, screwed over the outer thread of the base plate. In this sabot, three longitudal slots at 120 degrees each are machined, leaving just a small (quite weak) connection in top of the sabot. At the base of the sabot a radial groove is machined, leaving a small weak radial rim. Upon firing, the lands and grooves give the projectile rotation upon leaving the barrel. The centrifugal force breaks the sabot apart in three pieces over the three weakenings, throwing the sabots away sideways. The base plate catches the air stream and reduces in speed, separating from the streamlined projectile.
Due to the great reduction in cross section of the projectile it will have reduced drag which results in retaining great speed over longer distances, and a flat trajectory
Upon impact, the tungsten carbide penetrator will pass through the armour, causing spalling of red hot pieces of armour inside the enemy tank, as well as red hot –pieces of- the penetrator bouncing through the inside of the tank with high speed, igniting fuel and ammunition, either killing the crew.
The shellcase is brass made and measures 76,2 x 583R.
The Tungsten carbide penetrator weighs 1737 grams (1,73 Kg), it has a diameter of 38mm and a total length of 126,8mm.
The 17 pounder APDS-T projectile has a Vo. of 1200 mtrs/sec (3950 ft/sec) and could pierce a 204mm thick steel plate @30 degrees at 500 mtrs, and 185mm at 1000 mtrs.
The 17 pounder APDS-T was therefore able to knock out every German tank from every angle up to 1000 mtrs.
The 6 pounder APDS-T has a Vo. of 1234m/s (4050 ft/sec) and could pierce a 146 mm thick steel plate @30 degr at 1000 yards.
6 pounder posting:
http://www.wk2ammo.com/showthread.php?1137-6Pdr-(57x441R)-HE-(2x)-AP(3x)-APDS&highlight=apds
17/25 pounder “Pheasant”, #2:
http://www.bocn.co.uk/vbforum/threads/92195-17-Pounder-Drill?highlight=pounder
Regards, DJH
Attachments
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01 - 17 pdr APDS-T and 6 pdr APDS-T cartridge cutaways.JPG -
02 - 17 pdr APDS-T and 6 pdr APDS-T projectile cutaways.JPG -
03 - 17 pdr APDS-T and 6 pdr APDS-T backside projectiles.JPG -
04 - Tungsten carbide core 17 pdr APDS.JPG -
05 - 17Pdr Qf.jpg -
06 - Sherman firefly.jpg -
07 - Archer SP 17pdr Tank destroyer.jpg
