A 300 WM case lubed up with some imperial sizeing die wax and one stoke into a 7mm Mashburn die is about all the case forming your going to need to do, to get a net shape case.
Its that simple.
I have never had a issue with sizing just ahead of the belt.At least not with my Mashburn.
If you have a problem with tight cases.A few .001s off the face of your shell holder will typically solve that problem allowing the case to go farther into the die
Redding sells shell holders in sets with different sizes just for that type of issue.
I run a load of H1000 and a 168 Berger classic hunting bullet.For deer.
It almost matches my bench guns for accuracy....
dave

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Only accurate rifles are interesting.