Hard to know on a 5 shot group if you were losing concentration or if the load is inconsistent...I struggle with that too. Another thing I do is test loads at 50 yards to try to take wind and my skills out of the equation. Then move to 100 to verify once you find a good one.
Do you find 50 yards is far enough? I would think at that distance, unless something is way off, most loads are going to be tight.
I'm not opposed to it, just never considered it.
