[Edward Tinker]

I think its pretty cool, although I don't remember hearing of this cartridge. What I wonder is the rear diameter of the cartridge? Because if bigger than 9mm, then the toggle / breachblock would have to have been adapted?

The .41 Action Express is a pistol cartridge developed in 1986 to reproduce the performance of the .41 Magnum police load (which is a weaker-than-standard load) in semi-automatic pistols.

History

The .41 Action Express was designed by Evan Whildin, vice president of Action Arms, in 1986.[3] It was based on the .41 Magnum case, cut down to fit in a 9mmP frame, and using a rebated rim. Performance was compared to the ballistics of the 41 Magnum police load.[2] The .41 AE was thought to be a very attractive concept, as the rebated rim allows a simple change of barrel, mainspring, and magazine to convert many 9mm guns to 41 AE.

Ed