correct me if im wrong but i didnt think the rum cases could be reloded. i have a buddy that has a 338 rum and his come out of the chamber very hard sometimes after firing , more often than not actually. as i do have a 300 and 340 weatherby mag and reload both of these ive never had that problem, i say its because the ultra doesnt have the belt. if thats the case you have to buy factory loads or virgin brass every time it may take alot of the cost saving on ammo out of the picture plus rem sells weatherby 300 ammo at comparable prices to the 300rum