Regarding the 264 win mag. I have read on several occasions that the original factory load with the 140 gr bullet was using a double diameter bullet. The idea was to minimize bearing surface to mitigate pressures.
Not aware of any double diameter bullets used today. VLD style bullets tend to have a short bearing surface, which might explain how some are getting higher than published velocities with their 264 Win mag. Might be hard to prove as the majority of handloaders are not using a strain gauge to verify pressures.
