Fin Stabilised

[Lang]

I think currently all the major powers have smooth bore main armament in many of their tanks ( or are coming in to service) with finned projectiles.

Obviously a finned projectile will absorb a great deal of energy from the fin drag as it spins decreasing velocity and range. A very slow spin can still help stabilize finned projectiles and the current smooth-bore projectiles have the fins very slightly off-set to create a slow spin.

To get no spin or slow spin with finned projectiles with traditional grooved barrels they have "Obdurating Rings" which is a collar that seals the gas but slips on the projectile. There are also various discarding sabot designs that seal the gas but fall off once the projectile leaves the barrel. These are extremely bad news if infantry have close support from tanks firing over their heads!

I believe Mike's projectile would have been shot from a smooth-bore weapon but may be wrong.

Lang

[tankbarrell]

British practice is still to use a rifled gun for HESH projectiles.

[Lang]

Yes Adrian. The British are unique in having their main battle tank the only one of all the NATO countries to have a rifled barrel.


Here is an interesting discourse on fin and spin stabilised projectiles.

https://www.globalsecurity.org/milit...ets2-types.htm

[Ed Landstrom]

There's no mention of shaped charges (or did I miss it?). I've read that one reason smooth-bores are back in fashion is that if the projectile is spinning, the effect of a shaped charge is reduced. Maybe that's another myth.

[Lang]

Ed

I would surmise that a spin of say 10/20 turns per second for a finned projectile would not have much of an effect on an explosion initiating at many thousandths of a second. On the other hand a rifled barrel producing a spin between 2,000 and 3,000 rpm could well have some effect as you say.

It appears that the high tensile penetrating "bolt" is the go now to get the charge igniting after the armour has been penetrated rather than just a surface explosion from squash-head, shaped or conventional HE.

They are getting so sophisticated with Infantry man-carried anti-tank weapons that the tank-on-tank weapons we are talking about are almost superfluous as more than ever before in a conventional war with well equipped armies a tank is little more than a steel coffin and this is not taking into account aircraft like A10's, Mi-28 and Apaches. I think they are brave men surviving psychologically on a hope-over-experience mind-set.

This is pretty depressing if you are a tank man.
https://www.youtube.com/watch?v=CDctxC-7P9k

and this one
https://www.youtube.com/watch?v=y5xKCzdhAC8

And this would make you want to give the game away.
https://www.youtube.com/watch?v=myv7CAJ5Zpk

Lang

[motto]

I seem to remember hearing/reading somewhere that shaped charge projectiles have limitations on them as regards maximum velocity. They depend on the blast being focused due to the distance from the armour when detonated and if travelling too fast may even be knocked out of shape at the time of detonation. Maybe how squash heads were invented.
As I understand it, delivery systems for shaped charge projectiles tend to be relatively low velocity.

David

[Mike Cecil]

Dave,

MV of rounds fired from an L7A3 105mm tank main armament (eg Leopard AS1):

L52A2 APDS/T = 1,478 m/s
L35A2 HESH/T = 732 m/s
M456A1 HEAT/T = 1,174 m/s

I'm certainly no expert on the physics of shaped charges, but it seems to me the 'stand off' distance of the PIBD (Point Intitiating Base Detonating) initiator ie the distance from the initiator to the shaped charge, would be the critical factor. The higher the velocity at impact, the greater that distance would need to be to allow development of the slug by the shaped charge?

The M456A1 was fitted with a rotating Nylon band - the band rotated in the rifling, but did not impart appreciable spin to the projectile (which I think answers your query, Ed). The projectile included a set of tail fins for flight stability.

Mike