I'd also strongly recommend that, in addition to using a bench so minimize shooter induced error, that you shoot more than just one group before you rule out any one ammo. You've got a few different types of ammo, so why don't you shoot the whole box of each off the bench before you decide. Not only will that allow you to get an average group size for each ammo type, but it'll also allow the barrel to break in a little. I've ALWAYS gotten better accuracy after somewhere between 15-30 shots.

Mike