World War 2 Talk - View Single Post

MikB · 23-07-2006, 12:42 AM

You can see from the cartridges shown earlier that the 17pdr case has much greater capacity than the standard 75, meaning much more kinetic energy is available from the propellant charge. This bigger charge also requires a longer barrel to burn it in - 58 calibres long as compared to the 40 calibre long 75mm. The result with ordinary APCBC (full weight AP shot with a streamlining 'ballistic' cap) was MV of about 2950 - 3000 fps against 2030 - 2050 for the 75. Since kinetic energy is what pierces armour, and this increases with the square of velocity, that of the 17 pdr was more than twice the 75's.

The APDS traded projectile weight for even more velocity, and nearly doubled the penetration again.

What I've often wondered is why no-one tried to improve the performance of the 75 with APDS, since it was undoubtedly a handy gun for tank battles in woods and towns, especially with the Sherman's exceptionally fast turret traverse. Perhaps it was not possible to come up with a propellant that would burn consistently enough in the short barrel.

The performance of the 17 pdr Sherman Fireflies was very good. The German Tiger tank ace Wittmann was probably killed in a shootout with Fireflies, and I believe the Americans unsuccessfully asked for some. With the clout of a Tiger or Panther and better agility than either, their vulnerability was somewhat offset.

Regards,
MikB

23-07-2006, 12:42 AM	#8 (permalink)
MikB Senior Member Join Date: Jun 2005 Posts: 170	You can see from the cartridges shown earlier that the 17pdr case has much greater capacity than the standard 75, meaning much more kinetic energy is available from the propellant charge. This bigger charge also requires a longer barrel to burn it in - 58 calibres long as compared to the 40 calibre long 75mm. The result with ordinary APCBC (full weight AP shot with a streamlining 'ballistic' cap) was MV of about 2950 - 3000 fps against 2030 - 2050 for the 75. Since kinetic energy is what pierces armour, and this increases with the square of velocity, that of the 17 pdr was more than twice the 75's. The APDS traded projectile weight for even more velocity, and nearly doubled the penetration again. What I've often wondered is why no-one tried to improve the performance of the 75 with APDS, since it was undoubtedly a handy gun for tank battles in woods and towns, especially with the Sherman's exceptionally fast turret traverse. Perhaps it was not possible to come up with a propellant that would burn consistently enough in the short barrel. The performance of the 17 pdr Sherman Fireflies was very good. The German Tiger tank ace Wittmann was probably killed in a shootout with Fireflies, and I believe the Americans unsuccessfully asked for some. With the clout of a Tiger or Panther and better agility than either, their vulnerability was somewhat offset. Regards, MikB Last edited by MikB; 23-07-2006 at 12:48 AM.