I am a firm believer that no cartridge requires any more neck tension than .002", even heavy kickers.
On my comp rifles and some of my very accurate hunting rifles I run .0015" neck tension , this includes my 338WinMag, never had any bullet setback during recoil and they're not crimped. The most important factor, especially with the 300WinMag, is that the neck tension is consistent across all cases. I anneal every other shot with my 300, but this is a target rifle, in my hunting rifle I only anneal whenever the brass needs trimming.
Even my 375 Weatherby and 416Rigby only get .002" neck tension, the Rigby gets a crimp but the 375 doesn't.
As a side note, a few years ago I bought some old Kynoch 416Rigby ammo, not sure of it's age at the time, but the ONLY thing holding the bullets in the necks was the case mouth where it had been rolled into the cannelure! I pulled them all, resized the necks and reseated the pills, and they shot quite well.