I believe the 6.5 WSM can be formed either from 270 WSM or 300 WSM brass which (I believe) share the same shoulder. The 7mm WSM has a shoulder that sits farther forward. I form brass for my 6.5 WSM from Norma 270 WSM brass. I would bet that the Shilen and almost all 6.5 WSM chamber reamers are based on the shorter shouldered 270/300 WSM case. Only way to be sure is to call Shilen as you mentioned, Doug. Please feel free to correct me if I am incorrect on this, guys.
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