Well, there have been lots of rare and unusual cartridges mentioned here so far but no one has mentioned the legendary Mondragon piston cartridges. Anybody out there have any in your collection?

Yep - a nice 5.2x68, loaded with bullet, headstamped POLTE MAGDEBURG.

Tony Williams
Military gun and ammunition website: http://www.quarry.nildram.co.uk
Discussion forum at: http://forums.delphiforums.com/autogun/messages/

i also have a specimen of the 5.2 x 68 Mondragon , and a sectioned example as well . The base of the nickel jacketed projectile is pressed into a brass washer that seats on the top side of the annular ring around the case. The proj is approximately 1.206" long ( apologies - the battery in my digital calipers has died and only have imperial verniers ) and the washer travels some .585" before hitting the case shoulder .
The propellant powder is a cube style , presumably smokeless . Just thought this might be interesting...