A question regarding the construction of shrapnel shells

[Neville_C]

I recently acquired the base of a Boer War 155 mm Creusot "Long Tom" shrapnel shell and am trying to understand how the driving band was attached. The groove to take the band has an unusual, overly deep angled profile, which differs significantly from that on the common shell. A very poor reproduction of the diagram of the two types of projectile included in the handbook for the gun shows that the driving bands are identical, and that the additional space behind the band on the shrapnel shell is filled with an unidentified material.

Does anyone here know what that material was and how the driving band was fixed to the shell? Also, was this system unique to Creusot projectiles?

The final photograph below depicts five Creusot shrapnel shell bases. The one on the right shows the driving band detached, giving a partial view of the space behind it, which appears to be a void. Clearly this can't have been the case when the shell was fired.

 

[ThomasP]

Just a guess, but the engineer in me says the odd shaped groove maybe used as a crimping groove for the "koker" - possibly with the void containing solder? I can see a couple of potential advantages using such a design in terms of ease of manufacturing.

I cannot tell for sure from the drawing, but it looks like there are 2 layers of "koker" - an inner and an outer - with the base of the inner resting against the "bodem", and the outer "koker" crimped into the groove.

 

[JulienCD68]

Hello,
The french shell on the right is a Obus à Mitraille Model 1887.
I'll take a better photo for you soon.
The shell body has thin walls.

 

[Neville_C]

Thank you Julien, that is absolutely fantastic.

I hadn't for a moment imagined a scenario where the thin walls of the shell tucked behind the driving band, thus requiring an unusually deep groove. Indeed, I hadn't even realised that the base was completely separate from the body of the projectile.

Am I right in surmising that the driving band helps hold the two parts together?

I notice that the base of the Boer War Creusot shell is somewhat deeper than that of the Model 1887. Presumably this was a modification made before the Transvaal purchased their four 155mm guns in 1897.