I agree with Stubblejumper. 1/2" accuracy or better requires a that almost all of the factors influencing accuracy are tightly controlled to near perfection resulting in a very high level of consistancy. Let's be perfectly realistic here; <1/2 MOA is OUTSTANDING ACCURACY for any gun. That level of accuracy on a consistant basis (one or two lucky groups do not count toward the consistancy requirement) is hard to achieve even with dedicated, purpose-built benchrest guns, let alone a light sporter weight magnum hunting rifle.

A good quality rifle is just the start of an accurate SETUP. Now if you were to say that a custom rifle, with all the accuracy work done to it, should shoot MOST types of ammo into 1 MOA, I'd say that's not unreasonable. But even a great rifle with crappy or ill suited ammo won't shoot up to potential, nor will great ammo make a poor rifle shoot well. BOTH factors have to be matched to each other.

I've heard that the large capacity, over-bored magnums are somewhat finicky, often showing a lot of fluctuation in velocity which is a factory in accuracy. Both because a bullet that is faster or slower, all else equal, will hit higher or lower (respectively), and because velocity and pressure variations also change the harmonics of the barrel, resulting in less than outstanding accuracy.

Mike