I have an older 455 Super Match 20" barrel. I have reached out to 300 yards yet but I am ready. I put the rifle in an Oryx added a straight grip, a modest trigger job, an extended tactical bolt handle and a rear bag rider, with as swiveling, tiltable bipod.
I realized by the adjustment available on my Riton 6 x 24 x 50 scope, zeroed at 20 yards on the zero stop, I was not going to be able to dial it up much past 200 yards. I looked at the down adjustment I had left, and it was 55 MOA. I installed an MDT 40 MOA rail (amazing fit, just like the chassis). Since the rail added a bit of height, I went to shorter steel weaver rings so line of sight above the bore is similar to what it was pre-rail. I dialed the scope to where I figured it should be and at 20 yards at the range a couple of clicks adjustment for both windage and elevation were all that was needed. Once the zero-stop was reset, I dialed it up all the way, and now have a total of 60 moa (240 clicks) of up travel available. The rifle before the installation, depending on the ammo, 5-6 MOA to shoot to zero at 100 yards; which leaves me with 55 MOA to play with.
If you get a good deal on a nice, used 455 (they take the same barrels), it should shoot as well as a 457, and if you are going to change out the stock and other bits and pieces, it will serve you well.