The SAUM's are all but gone because Winchester had/has the short magnum market locked up tight. I bet the new RCM's will also go the way of the SAUM's.

Metric cartridges have never been incredibly popular in America. The only two that have ever really made it have been the 7mm Rem mag and very recently the 7mm-08. The .280 has never been all that popular either. Most all metric designated cartridges have had lack luster sales compared to other "American" cartridges.

And early on Jack O'Connor helped solidify the .277 bullet diameter in American history. So much so that the .280 just couldn't catch up.