I keep seeing the term "aggregate" used to best assess rifle accuracy. Can someone explain how this is calculated and determined. I would like to report on my rifle's accuracy, but seems like it ought to be expressed as an aggregate. How? Note, I do not compete, but keep targets and determine group sizes.
Thanks.
Phil
http://internationalbenchrest.com/about/whatis/disciplines.php
A typical sporter-light varmint-heavy varmint benchrest match is 5 shots; 10 shots for unlimited/heavy bench. Group size is measured center-to-center. Match winners (smallest group for a single match) are very often in the zeros (<0.100") at 100 yards, and rarely out of the ones (0.100"-0.199") unless conditions are horrible.
A yardage aggregate is the average of 5 matches (groups), adjusted for distance. At 100 yards the 5 groups are simply added and divided by 5, and reported to 4 decimal places. For example, if a light varmint class competitor had 5 groups of 0.050, 0.100, 0.100, 0.150, and 0.100, the range aggregate would be reported as "light varmint 100 yard aggregate 0.1000."
In a competitive shoot under ordinary conditions, winning 100 yard aggregates are very often in the ones.
At 200 yards the 5 groups are added and divided by 10 (to make them directly comparable to the 100 yard agg). At 300 yards the 5 group measurements are added and divided by 15 to calculate the range agg.
Grand aggregates are calculated as the average of the range aggregates (e.g., heavy varmint grand aggregate 100-200 yards), and multi-gun aggregates are calculated as the average of the grand aggregates. Winning a 3-gun (SP, LV, HV) or 4-gun (SP, LV, HV, UNL) agg at a big shoot is the pinnacle of the sport.
Aggregates matter more than single groups for many reasons. Among them:
Statistics. "The bullet has to go somewhere," and "even a blind pig finds an acorn once in awhile." The smallest group that a rifle can shoot is
not a reliable indication of its precision. Small groups are a function of
sample size and precision. Note that the 6PPC is -- by a country mile -- the winningest cartridge for benchrest shooting at 100-300 yards, yet has
never held the small group record at 100 yards for a bag gun.
Shooter skill and consistency, especially under the time pressure and competitive pressure of the game, shot in real-word conditions. Most common lament at a benchrest shoot: "I put the first 4 in a bughole."
One foggy morning I shot this 0.029" 5-shot group at 100 yards with a Seeley Masker 6PPC cruiser. A .308 bullet won't go through the hole made by 5 6mm bullets. Does that mean that this rifle will shoot in the zeros "all day long"? Hell, no.
I've also shot two zeros in registered benchrest competition, handily won the matches, had the small groups for the day (still have the little wood plaques!), and wasn't in the Top 10 for any of the aggs. The really good rifles and shooters win the aggs.
I posted a pic of my best 5-shot 300-yard group, too, shot with a Borden-smithed Panda LV (in 6PPC, of course). "The first 4 were in a 0.104" bughole."
(I know it's a 200-yard hunter target -- I was shooting at 300, though -- just practicing.)
If you want a rifle that is guaranteed to be capable of a 0.250 agg at 100 yards, you're wasting your time with anything other than a full-on benchrest rifle. Besides, the fastest way to learn to read conditions is to have a rifle that doesn't lie to you.
P.S. No "called fliers," no "do-overs," no "practice targets." Every single shot on the record target counts.
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