[G56]

That's unusual, bottle neck cartridges are normally designed with a taper to ease extraction after firing, I wonder why they didn't design this one that way...

 

[G56]

I actually have a round of 30 Mauser, I ordered a bunch of 9mm once fired brass when I first started reloading, right at 40 years ago, and there was one live round of 30 Mauser in the bunch of brass! I had heard of the caliber but never seen the cartridge before, since it is a fairly obscure caliber.