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Old April 17, 2018, 01:29 AM   #78
Join Date: February 12, 2001
Location: DFW Area
Posts: 21,855
If you are aware of a mistake, the 'called flier', you don't include that shot in the group measurement.
If you know for sure you made a mistake AND you know for sure which shot on the target was the mistake then I suppose it would make sense to discount that shot and shoot another one to make up for it. Except of course if the goal is to evaluate the worst case performance, in which case the mistake probably shouldn't be eliminated since it certainly contributed to a worst case performance.

I'm not really in favor of trying to pick and choose which shots to keep and which ones to leave out when shooting groups because...
If you make a mistake that you aren't aware of, then how do you label a shot a mistake if you are not aware of it being a mistake?
Well said.

There's also the situation where you know you made a mistake but you're not sure which shot on target it is. Maybe the "flier" that is high and right is the mistake you know you made, or maybe it's telling you about an ammo problem or a gun problem, and the actual mistake wasn't actually as bad as you thought it was. Once you start trying to pick and choose shots or groups, then you're never really sure if the numbers are telling you about how the shooting is going or if they're telling you how good you are at throwing away shots or groups to make the results come out the way you want them to.
How many samples do you have to take?
A simple and effective way to know if you have enough is to stop when the average isn't changing significantly any more. If all the groups are fairly consistent then it will stabilize very rapidly.

Or, you could just pick a number of groups you want to shoot and pick the number of shots per group that seems reasonable to you and go for it. Five shot groups are pretty common for handgun accuracy evaluation and averaging a handful of those should provide decent results. You'll see that approach commonly used in published reviews.

I've seen much larger group shot counts used for accuracy evaluation, but only with machine rests, or when some similar technique is used to take the shooter out of the equation as much as possible.
Do you know about the TEXAS State Rifle Association?
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