I know that the 222 has been necked up to a 243 caliber for benchrest shooting, called a 6mmx47 or something like that. My question is, has anybody ever necked up the 223 to a 243? If so what is it called, and how does it perform?

The 6mm/223 is also known as the 6x45mm. That is about all I know about it. The 6mm TCU is also made by necking up the 223, but it is .010" shorter and has a sharper (40 degree) sholder. It was made for the T/C contender, and is a pretty good varmint cartidge. I'm not sure what the metric designation of the 6mm/222 is. Mabey someone else will come along with more info. Hope this helps,Ron.

6x47 is the .222 Mag necked up to 6mm. Not the .222. Just a clarification.

__________________
MikeG

Thanks!!!!!!!