dang it all .. i just have to agree with ole swampy..
the majority , i cant say its 92% as swampman says, but the majority is IS human error when not getting a descent group.
and stating that factoid of info does not make him, me or anyone else a jerk.
if you have ever spent any time as a range officer, or have taught a group to shoot you'll soon find out that its is usually the human error and not a bad barrel or heavy trigger thats the issue .. whether your on this or that side of the pond.