Originally Posted by czech1022
I could get a 7mm Rem Mag neck sizing die (Lee Collet die?) and seldom need anything else.
Originally Posted by nsaqam
The 7mmRM Collet die wouldn't work because the case on the 300WM is longer than the 7RM. The LCD's need the entire case inside the die so the shellholder can push directly on the collet.


czech1022 & nsaqam-

The 7mmRM case is 2.500 inches long. The 300WM case is 2.620 inches long. The difference is 0.120 inches.

The 7mmRM Lee Collet Die may be made to work with the 7mm-300WM case by using a washer of 0.120 inches thickness with a hole just a bit bigger than case diameter. The case is put into the shell holder, the washer put over the case so it rests on the shell holder, and then the case is run into the 7mmRM Lee Collet Die.

It is possible that the internal shape of the 7mmRM collet may cause it to bear on the shoulder of the 7-300WM case when the neck is sized. The neck of the 7-300WM case is shorter than the 7mmRM case by about 0.007 inches. The diameter at the shoulder of the 7mmRM case is about 0.002 inches greater than the 7-300WM case. Both have a shoulder angle of 25 degrees.

If the case shoulder does happen to bump against the internal collet shoulder, then a possible solution is to use a slightly thicker washer. This will cause the neck not to be squeezed full length by the collet, but this should not make a lot of difference. Alternatively, Lee will make a custom collet die for not a whole lot of money.

--Bob