I believe the V-bull is usually about 1 moa for standard target shooting (diopter sights) & smaller for PR. (3.3" at 300 yards)
Not too many people can keep all their shots in the V-bull though (me included) Supported & with optics it's a different story of course.
A GOOD fullbore shooter should keep the majority of his shots within the Bull area so I'd say around 1.5 moa or better.