I have the 300 RUM myself, and other then the brain rattling recoil, its a real blast to shoot,lol. I thought the idea behind a 30-378 would be cool, but the recoil has to be intense, not to mention the muzzleblast. From what Ive seen, brass costs more, that much more retumbo or H1000 to buy, and with the severity of the case to bore ratio, not a significant gain over the RUM. Either way, unless you're pushing the 180-200 grain bullets, IMO you arent taking advantage of the big boiler room they put in there. I just got into reloading here, and with a 7mm rem mag already, I think I'll be focusing on the 200 grain rounds for the 300, and lighter bullets for my 7mm.