Originally Posted by JohnKSa
The bottom line is that a X MOA shooter with a Y MOA rifle will shoot groups that are larger than the larger of the two accuracy figures but smaller than X+Y MOA.
It's called the Root Mean Square (RMS):
Shooter^2 + Rifle^2 = Group^2
A 1 MOA shooter + a 2 MOA rife will produce, on average, a 2.24 MOA group.