The main reason I woulddn't do that is I simply have never liked the 6mm Rem! It seems most others don't like it either considering the 243Win out sells the 6mm Rem by five fold! No good reason, just what most seem to want, myself included. You are correct, though, it would be a lot easier.

There is nothing wrong with a 6mm if that is what one wants, but I don't want one, and prefere the 243 Win. No reason just a personal thing, it just happens to be one of my all time favorite cartridges. I had a custom rifle made in the wildcat 243 Page Pooper, long before Winchester came out with their version of that wildcat calling it the 243 WIN. SO, I have a long history with the 243 Win.

It would be no harder to make the 243 Win Rimmed from 444 brass than it would to make the 6mm from 444 brass. The 6mm Rem being a 7x57 case necked down, is no better than a 308 case necked down, and I think the easiest way to get what I want is to go with the 307 Win simi-rimmed case necked down to 243, with the 307 being the same case as the 243 win with a simi rim. Of course the 9.3X74 case will be around a lot longer that the 307, 0r the 444. Both those rounds are nearly dead in the water. However I could form 1500 rounds of either, and have brass as long as I'll live at age 72! The 308/307 case is designed for much higher pressures than the 444, or the 9.3X74R cases, so would be less stressfull on the double than the other two. The 7X57R case would be strong as well.