You would have to set the barrel back, as the 6mm case has more tapper from the base to the bottom of the shoulder than the 243 does. A 6-284 reamer would clean out the 243 chamber without setting back the barrel and would show a significant velocity gain with bullets in the 70 to 95 grain range. If you don't over-heat it, it might even last for 8,000+/- rounds.
Jeff
