Searching for some info for something else, I found a site with some good info on assault rifles at http://www.quarry.nildram.co.uk I borrowed some pics and data:

From left to right: 7.62x51 for scale, 6mm Lee, 5.2mm Mondragon, 5mm Sturtevant.
I know [I think?] that Mondragon was a Mexican army officer but can anyone shed any light on this cartridge? Most unusual shape and I can only wonder how it worked.
Anyone have any inof?

Taken from the cartridge collectors website ( www.cartridgecollectors.org )


5.2 x 68 mm Mondragon (with piston)
Specimen and photos courtesy of Paul Smith



This was one of the earliest small calibers rounds. It was designed by the Swiss Colonel Rubin in 1894 for a semi-automatic rifle to be built by the Swiss, the rifle being a design by Mexican Manuel Mondragon. This was the first semi-automatic rifle to reach production (although by then chambered for conventional 7 x 57 mm Mauser cartridges. It was made in limited numbers (about 4,000 total), and after Mexican default on the contract the remaining rifles ended up being sold to Germany where they were used as aircraft weapons during World War I.



The projectile has a cupro-nickel clad steel (CNCS) jacket and brass ring at the base.



According to the Rubin’s patent, the piston ring around the base of the bullet allows for more energy to be used to drive the projectile than a conventional design. The piston ring is stopped at the shoulder while the projectile continues down the barrel. The projectile is 31 mm in length and had a muzzle velocity of about 800 m/s (2,600 f/s).



Visible on the outside of the case is a smooth cannelure. The piston ring sits on this indentation. Presumably the case is necked after the projectile assembly has been seated.