Re: 270-7 WSM
To be honest, the only thing you need to do is seat a boattail bullet of 7mm diameter in the standard 270 WSM case.
I prefer Ballistic Tips of Accubonds as their solid base will not deform to the slightly higher seating pressures as the bullet itself expands the case up the needed 0.007" of an inch from .277"(270) to .284"(7mm).
Also, just running the brass through a 7mm WSM die will expand the neck as well.
You can also buy a standard 7mm WSM sizing die and take it to your local gunsmith. With carbide cutters you can easily take off 0.050" of the die length to allow for the slightly shorter 270 WSM parent case.
To be honest though. I would suspect the standard 7mm WSM with Winchester brass will serve your needs very well.
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