I'm going to jump back in here for a moment with an observation from another predictive. One year I was shooting matches in Raton NM at the NRA center, I just happened to be shooting next to G. David Tubbs at the time. So, we started talking in one of the breaks about the .243 Win and the then newer 6XC that he developed, which came out of the 6X he worked on before the 6XC. I was very interested in the 6XC at the time due to a conversion I was thinking about on a .22-250 Rem in a Weatherby MkV Varmitmaster, but I digress'.., so I asked what he thought of the .243 Win mainly because I knew he'd used that cartridge numerous times in LR matches; G. David said he loved it, adding the only reason he didn't stay with it was because it washed out barrels (as a match rifle- not hunting) in competition and he was always re-barreling after which he'd have to find a new "sweet spot load again" for the new barrel, and that took time, that was the reason for the 6X (which is very close to the old 6mm International) and later the 6XC they were superbly accurate as is the .243 Win, however... they didn't wash out barrels as fast. So, bring that conversation around to the .243 Win and the 6mm CM and I think that's where the real advantages between the two is found;.., as hunting cartridges, there's no argument they are pretty much equal, as match cartridges again they are equal'.., except the .243 Win will have to be re-barreled sooner. Now with the above said, I understand cartridge length and rifle magazine advantages in a slightly shorter over-all cartridge length help's with longer bullets, that's not the concept of cartridge performance, so let's not lite that dumpster fire. Just my .02