Here is a post on my 416 Buff that has lots of information.
https://www.longrangehunting.com/threads/416-buff.21003/
Just a few points for this round = it is a 375 Rum necked up to 416 nothing else. it pushes the 400 grain to 2700 ft/sec without pressure
And is one of the most accurate rifles I have. It shot my best group ever (.034 thousandths @ 100 yards with the 400 grain bullets and a 5 power scope),
It realy performs with the 350 grain Swift A Frame and can get very close to 2900 ft/sec velocity without pressure signs.
I have a 416 Rem Mag and at temps over 100o it gets a little dicey so the 416 buff was the answer to more velocity with less pressure.
Dave Manson made my reamer and it is not propitiatory, Hornady made a fine set of New dimension dies foe it and I sized 200 cases with zero losses.
Hope this information helps you.
J E CUSTOM