25 x 173?

[Fred]

Hi Folks
I recently obtained a auto cannon round with the case dimensions 25 x 173mm. It has a green steel cartridge,similar to some Oerlikon cases I have seen and a TP projectile.the headstamps are BM 100 96. I cant find refrences to this size of case anywhere, has anyone encountered it?
Thanks for any input
fred

 

[Quatermass]

Oerlikon 25mm KBB, short case round.

Quatermass

 

[Fred]

Thanks Quatermass. It looks very similar to the 25 x 184 Oerlikon. I was surprised that I couldnt find any refrences to it with the usual searches.

Fred