MZ5,
Yeah, I've grown a little weary of standard deviations calculated from 5-shot strings!
I have gone to ten shot strings over the chronograph.
I keep a log-book for each session and tally-up multiple shot strings over time. Depending on how many range sessions you get to, over a few months you can have a few dozen shots cataloged.
That gives you, I believe, a very valid look at your rifle's accuracy, load consistency and a measure of your skills at the bench at home and on the range.
