Hi Mark, yes, you can use the 7mm Rum die but you will have to cut it back with a grinder and cut off disc (have done this before). The RSAUM die will work as well providing you have a long stroke press. If you want a generic neck die, the hornady 7mm Magnum Neck is the correct die.
The price of the dies are not a deterant as much as me getting time to work on it. I was thinking of making a winter project out it giving me more time. I recently picked up an orginal Mashburn Arms.Co. barrel in 7mm super mag. the barrel is only 22 1/2" long making me think of a light mountain style rifle.
This auction is for 1 box (20rds) of Mashburn Cartridge Company 7mm Mashburn Super Magnum 175gr SP` This is factory fresh ammo. Very limited supply. We are a licensed ammunition manufacturer. Please check out our other auctions got questions e-mail or call 903-852-5012 When you buy from us you can expect: No Credit Card Fees