Fin Stabilised

[Tony Smith]

Originally Posted by Mike Cecil

I was in Atlanta Georgia earlier this week, ....

Associated with the Cyclorama is an excellent museum of Civil War objects, including a wide range of rifles and pistols with good, detailed captions, not the 'one liners' we so often see in museums these days. There is also a fine collection of ordnance and projectiles, including this rather interesting 'fin stabilised' experimental projectile manufactured by a Confederate armory. The caption states it was a winged projectile for increasing the range and accuracy of smooth-bore cannons. The wings were spring-loaded and extended upon the projectile leaving the bore.

Mike

Ahh, museum captions. I hope one day there will be a museum that records and displays all those one liners!

The projectile shown is not for a smooth bore cannon. It has "buttons" that engage with rifling, which was used in the Armstrong breech loading rifled barrels.

[Mike Cecil]

Hi Tony,

I see no buttons....?

Seriously,Tony, I'm familiar with the Whitworth & Armstrong systems, but I didn't see any lugs/buttons on the projectile's outer edge that could engage any form of rifling. The caption was quite specific about the development (but of course, we all know how accurate many museum captions really are!)

Mike

[tankbarrell]

Fin stabilization was hardly new, even then. Arrows spring to mind!

[Tony Smith]

My apologies, Mike. I need to open pics and look closer, or clean my computer screen. While not as large as the big brass pads on British projectiles, I thought I saw small "nipples" or lugs, which I thought were the American version of an experimental round.

[Mike Cecil]

Happens to us all, Tony: I made the same error when I took a quick look at Colin's post on the smoke dischargers - didn't comprehend the scale and assumed (embarrassingly!) that the spent cart was a 12 # not a .303!!

Mike

[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.