well....the 6mm-222 is just what it says(as far as i know).

the 6x47....is a 222MAGNUM case, necked up to 6mm.

the 6x45....is a .223 case necked up to 6mm.

.......and the 6TCU is a .223 necked up to 6mm, and then fireformed to an improved shape with 40 degree shoulders.



i've shot the 6x47, and currently shoot the 6tcu in 14" contender pistols. they are sweet!