I've shot more than a few M1 Garand's and most will hold sub 2.5moa with decent ammo. Two national match rifles I've shot with 308 barrels would do under 2.5" at 200 yards prone, I shot my first 200 yard rapid "clean" 200-6x with one of them. If you sent them to Fulton, that can get you below 1.5moa with decent ammo.
That's what I'd do if I were building one.