I tried to read it all and I will comment where I should. I studied 458 WM and Lott. I decided to go Lott because I’m a reloader and components are same price, but I can get more out of the Lott. I’m not afraid of load testing near max either.
First a comment about Hornady data. That is not really 458 Lott maximum data, IMO. That said there is none that I can find out there. Like most straight wall cartridges, in my hunt for max, I found pretty severe load compression....that’s ok, I also found the velocity I was looking for.
I have the Winchester 70. It is a late New Haven Safari Express rifle with the old trigger. Dennis Olson out of Plains MT converted to Lott for me. He also shortened the barrel, corrected the bedding, regulated the trigger, lengthened the pull, put a Kickeeze pad on it and updated the sights.....Amazing rifle! Very easy for me to shoot heavy loads from.....although, I’m still developing my appetite for those!
I believe the conversion was remove the magazine block, lengthen the bolt stroke, replace or adjust the ejector and rechamber, but I never asked for the full story.
500’s at 2300fps, this is a real stopper on a reasonable budget