The 375 JDJ was a premium chambering for the Contender, and taking it on down to 358 would certainly make a fine cartridge, or even a 375 Winchester, making a 35/55 I guess. To bad there is not a single 375 or 400 bore in the lineup.The 444 is an excellent base for many cartridges, but the main platform for wildcatting has been bolt rifles for a long time, so except for Mr Jones, no one has worked much with it. It has been described as a rimmed '06 case, pretty close in capacity.