Here's the "original 10mm Supermag based off the 8mm case.
Ease of feeding from mags!
Ease of proper feed into chamber through AK trunnion opening!
Ease of case sizing.
It looks cool...very similar to 401 win self-loading
8mm brass designed for high pressures and should last for many reloads.
Hard to find good brass.
Most brass is berdan primed
Tends to be expensive.
Wide variety in wall thicknesses below bottleneck on the 8mm brass experimented with.
I still kind of like this one. I had originally planned on using off the shelf 8mm dies for sizing which left it just a hair loose and would have required a special taper crimp or roll crimp. That was what the casemouth headspacing concern was. Now that I'm doing custom reamers and sizing dies, I could adjust the taper on the forming die a hair and make for tighter neck. Getting boxer primed, once-fired 8mm brass is still a challenge, though.
Like all projects, every aspect of this has had its good and bad points. Getting a blunt nosed cartridge with a .532" base to feed from a mag,through the lug opening, and into the chamber reliably is still a looming concern. I should have the reamer done this weekend and should be able to test some of this next week. The barrel can still get another couple inches chopped off if I end up needing to rechamber.