You won’t hurt anything to have a gunsmith open the boltface of a .223rem 700 to fit the 6.5 Grendel, but you may struggle getting a mag box to feed appropriately for the smaller round. THAT will be the trick of the project.

I expect you’ll be considerably better off to purchase a Ruger American, CZ 527, or Howa Mini action rifle in 6.5 Grendel and simply sell the 700 SPS.