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.
Azshooter - Yes, you're right about the two diameter bullets. I've got some old Winchester bullets for reloading as well as some Winchester loaded factory ammo, both from the early/mid 1960s, that are the two diameter bullets. I've also heard tell that some of Winchester's current 264 WM factory loaded ammo uses similar two diameter bullets but have yet to actually put my hands on any, so I'm not sure that tale is true. I did locate some two diameter bullets in .264 a few years ago sold by Midway and supposedly made by Remington that are Corelokts. I just recently tried them and to say they were inaccurate would be an understatement. 3-5" "groups" at 100 yards was what I achieved. I suspect they were poorly made and are unbalanced (sort of like the shooter!).
You may be right about the newer VLD bullets and shorter bearing surface yielding higher velocities. I've shied away from them since I'm working with a pre64 Westerner that has the slower twist so thought the longer bullets might not stabilize. Maybe I should give them a try and see how they do.
