This is from Nathan Foster, the 7mm Practical guy when I asked him about using a RUM or RSAUM die to form cases:
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.
Before you go too far, check the body diameter of your reamer to make sure that you can use neck sized .300 Win Mag brass. If the body diameter of the Mashburn reamer is smaller than factory .300 Win mag brass, you will need to contact Hornady and have them make you a full length resizing die, they will also need the reamer measurements. Lonnie Hummel is the man to speak to, he is very good, makes excellent custom dies. It took me quite a while to obtain the ideal reamer body diameter for the Practical so that it would easily (and continually) utilize neck sized brass. If you find that the Mashburn reamer is going to be difficult to utilize, the 7mm Practical reamer can be obtained from PTG and is pretty inexpensive.
If you get stuck or are confused about any of the above, please get back in touch.
Cheers, Nathan.
