Some agg's are for eight 10-shot groups at 100 and 200 yards.
Sierra Bullets used to use a 1/4 MOA average at 100 yards (California plant) and 200 yards (current Missouri plant) for their match bullets with 10-shot test groups. They now require all match bullets shoot inside 1/2 MOA at 200 yards. Effectively the same thing.
Hornady match bullets have to shoot 10-shots inside .950 inch at 200 yards.
Both shoot many test groups during production runs.
How credible is one group to represent real accuracy level?
Single group size times max/min multiplier equals approximate size limits of 19 out of 20 groups fired with different numbers of shots per group.
Shots/...... Multipliers
Group ____Max ____ Min
3 _______ 2.45 ____ .40
5 _______ 1.53 ____ .67
10 ______ 1.27 ____ .81
20 ______ 1.12 ____ .89
30 ______ 1.09 ____ .92
50 ______ 1.06 ____ .95
Examples:
If first 5-shot group is 1 inch extreme spread, 19 out of 20 will be from 1.53 inch to .67 inch.
If first 3-shot group is 1 inch, 19 of 20 will be from 2.45 inch and .40 inch.
Here's a good learning tool about groups, aggregates and the statistical reality of shooting groups:
http://azbrs.com/past-match-results/
Pick any event, such as
http://azbrs.com/downloads/results/2016-Cactus_Classic-Heavy_Varmint_100yd.pdf then check out the top 20 competitors' group sizes. Then compare them to any other day's Heavy Varmint 100 yard scores and note the group sizes are again, all different.
Had a long talk with a statistician who was also a rifle shooter and he says that all fired groups fall into these categories;
40% of them are about average size.
30% are a little bigger or a little smaller
20% are a lot bigger or smaller
10% are either huge or tiny.
Consider the record benchrest 5-shot group at 100 yards being .0077" shooting a .30-caliber cartridge listed as a 30 PPC,. Its holder has no other records or match wins to his name. It was the tiniest group anyone has ever shot in competition at 100 yards. His others must be too large to talk about.
