The IMR is mfg'd by General Dynamics in Quebec, the Hodgdon is by Thales via ADI in Australia. The Extreme coatings used are not a universal property, but designed around very specific conditions. Although they don't like telling you what that is, it would appear that the cartridge type designed for is the 22-250. That may, or may not, apply to the 308 case. Won't mean the powder won't perform, just that the "extreme" properties may not be as much as hoped for.