Re: opinions needed
Personally, I would sell the M77 and buy a used Vanguard or Howa. M77's have issues, not the least of which is the angled front action screw. There a lot of Tang Safety M77 fans out there, it shouldn't be hard to sell.
Both are great cartridges, my vote goes to the 6.5x284.
You will never know how much it has cost my generation to preserve your freedom. I hope you make good use of it.
~ John Quincy Adams