Re: 300WSM/IMR4350/165 GMX Help
I wish I could help more but I have not loaded GMX for my WSM because Fed Prem TSX is sub moa.
The safe loading "rule" for copper as I understand it and don't take this as gospel is to: use the jacketed lead minimum as the copper maximum.
I recommend a call to Hornady.
“Ask, Listen, Learn, Grow”
"Quit worrying about the little things, good luck and god speed"