The 6x45 is a wildcat. It was originally a TC encore chambering. The 6x45 is a solution to a problem that has been overcome by the 6.8 SPC or the .300 Whisper.

It falls short of the .243, but hits harder than the .223. it would be ok for CQB or coyotes up close. It also makes an AR legal to hunt deer and antelope at closer ranges while using a low cap mag.