I got to looking at reddings form and trim dies the other day and made an amazing discovery. You can call me genius. By using the 375, 338, and 300rum form and trim dies (about $23 a piece)+ a fl size die you can form the RUM cartridges easily. The only other option I have seen is RCBS form and trim dies for the 300RUM, and the cost on them is about $250, and you still have to buy a fl size die seperate. I bought the 375, 338, 300, and 7mm form&trim dies for about $100, and with a thin film of Imperial sizing die wax it works great.