I came full circle myself with the 7mm Remington mag, my first was way back in '79 and I have since fooled around with several 7mm STWs and one 7mm RUM. The RUM was just awesome, but I quit hunting where I had to take super long shots. Then, after playing with a 7mm Express (280) I just had my rifle rebarreled and converted to 7mm Remington Mag BUT with a 26" Remington factory barrel. I used the new R26/160 Sierra HPBT for over 3150 and R33 for over 3000/175 Sierra SBT. I am jazzed with both. I have a Nikon 4x12 AO on it and am "in the berries"! My next bullet to work up a load for will be with the 175 Partition/R33. I like having the extra velocity w/o the fireforming/dies of the 280 AI. All things considered, the 7mm Mashburn Super Magnum would be my first choice if I were you!!!
A slightly modified 300WM case and a heavy 7mm bullet just seems "right". When/if I get tired of this Remington mag, I will have it reamed to the mashburn. Good luck to you though Pard!