My first wildcat: 6mm-223

[Jack]

The 6mm-223 isn't quite the same cartridge as the 6mm TCU.
In the TCU series of cartridges, the shoulder angle is very steep, and the neck is very short- to maximize the amount of powder the case can accept.
The 6mm-223 is a straight neck up of the 223 case, retaining the original shoulder angle of the 223 cartridge.
Both cartridges use the same parent case- the 223, but the chambers are cut differently.