Coy, you are correct that Nikon's M-223 scope is set up around the .223 Cal., 55 grain polymer tipped bullet with a MV of 3240 fps.
That being said, I have shot some slower rounds and impacted 10 in. steel plates at 400 yards without a problem.
If you decide you are going to consistantly shoot your 2800 fps ammo, you may want to consider Nikon's M-223 with the BDC reticle. I would aslo suggest you checking out Nikon's Spot On Ballisitic Program to more finely tune your rifle,scope and ammo. This will give you more exact distances for each BDC circle. When predator hunting, I like most fo my friends sit and range objects just in case I don't have time to range a particular animal. Makes for much faster target acquisition. I have shot all the M-223 Series scopes, except for the 1-4 PBR out to 600 yards and had successful hits. Actually went 10 for 10 at 600 yards one time thanks tot his scope because I surely am not that good a shooter.
Drop me a note if you have any questions.
Bart