WW2 German case dimensions required please...

[ammofo]

I've just picked up a WW2 German case (1940) for the 10cm M14/19 Field Howitzer. The stencilling on the side identifies it being for a captured Czech gun.
I just want to check that it's not been cut down but can't find any dimensions for the length of the casing. I don't think it has been cut down, but I just want to put my mind at rest. (Mine measures about 180mm long.)

Incidentally, the bottom has some large red stencilling which looks like 'OBD' - does this mean anything to anyone ?

 

[Hoeksel]

182mm is the length

 

[flak18]

OBD is normally found on the closing cup in the mouth of the case..... not too sure of the exact spelling...Ohne Blei Drachte...which means without decoppering foil.

 

[ammofo]

Thanks Hoeksel for the length confirmation, much appreciated. Thanks also to you flak18 for the 'OBD' - here's a couple of (poor) photos so everyone can see what we're talking about...including the 'OBD' on the base.View attachment 126934....so now the only question I've got is...."what on earth is de-coppering foil and what's the significance of it ??!!"

 

[HAZORD]

The copper band around projectiles serves as a seal to keep the majority of the propelling gases behind the projectile and to engage the rifling of the barrel, to impart spin on it to stabilize it in flight. De-coppering materials are usually inserted into the powder charge to minimize how much of the rotating band material stays behind and coats the rifling. The combination of the very hot gas, friction, and pressure against the rifling tends to cause the copper to weld itself to the steel and fill in the pits and tooling marks in the barrel.

The U.S. Navy has typically used playing card size and larger pieces of Lead foil inserted in the mouth of a case filled with propellant, as a decoppering agent. Recent developments in smokeless propellant have created some new small arms powders, that minimize copper buildup in small arms barrels from the copper jacket materials of the bullets. Stainless steel and chrome-lined barrels typically have less copper buildup than steel barrels. Polishing and lapping the tooling marks out of the inside of the barrel will also minimize coppering. Coppering is usually removed with ammonia-based bore cleaners. Copper in the barrel will eventually degrade accuracy and it causes a galvanic action with the steel, degrading the surfaces.

https://en.wikipedia.org/wiki/Decoppering

 

[ammofo]

Thanks Hazord for this detailed answer to my question. If the use of such de-coppering materials is so important, it makes me wonder why ANY case would not have it included in the powder charge.

 

[flak18]

Some of the German projectiles did not use copper driving bands, instead using sintered iron.

 

[ammofo]

Nice answer !!
Just had to look 'sinter' up and I guess the sintered iron was more likely to disintegrate back into a more powdered form - rather than smudge into the barrel rifling like copper.
I've learned a lot from this one single case - so thank you to everybody who has contributed to this topic...I hope others have learned from it too !!