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Old April 18, 2018, 12:22 AM   #82
JohnKSa
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Join Date: February 12, 2001
Location: DFW Area
Posts: 21,702
Quote:
If a shooter includes known fliers in their group measurement...
If one is absolutely certain that a particular shot on the target is a flier then shooting an additional shot in that group and discounting the flier could make sense under some circumstances.

If there's any doubt at all about which shot is the flier, or whether or not the shot really was a flier, then throwing it out might make the shooter feel better and the group smaller, but now there's something other than the shooter's ability, the gun and the ammo contributing to the results.

Just throwing it out without shooting another shot doesn't sense as now the group being evaluated is a smaller number of shots than originally intended which means it isn't comparable to the other groups shot.

And, of course, if the shooter's ability is a big part of what is being tested, then throwing away "fliers" doesn't ever make sense because fliers are clearly saying something about the shooter's ability.
Quote:
If one is trying to evaluate their worst case performance, they should shoot blindfolded.
The comment I made about evaluating worst case performance was specifically in response to the comment that "the most important statistic is the largest group". The "largest group" is clearly the worst case performance for that shooting session. Of course there are really stupid things (like shooting blindfolded) that a shooter could do to make the worst case performance even worse--but I'm not sure what that would prove.
Quote:
There is variability even with multiple groups shot from a Ransom Rest, so stability in group size is a bit of a myth.
Yes, of course there is variability even from a machine rest. However stability in group size isn't a myth unless one chooses to unrealistically define it as "absolutely no variability in group size". A gun/ammo/shooter combination that consistently shoots 5 shots into, say, 3" groups, plus or minus a quarter of an inch at 25 yards is shooting pretty stable groups even though they're not all identical.

But a shooter whose groups vary by a factor of 2 or 3 clearly isn't shooting stable groups. Could be an ammo problem, a gun problem, a shooter problem or a combination.

By the way, using a machine rest doesn't guarantee accuracy or consistency--it only eliminates shooter error. If the ammo or gun is the problem then there's nothing a machine rest can do to fix the problem.

The article is interesting--the author's main point is that even with very consistent ammunition velocities (and a machine rest), it is still possible to get inconsistent results.

That doesn't mean he's saying that stable groups are always impossible, he's just showing that one can't assume that consistent velocities = consistent accuracy.
Quote:
But that does not mean there isn't a better way.
Correct. But it's certainly a better way for performing a typical handgun accuracy evaluation than shooting 25 shot groups by hand and then picking the largest one as being representative.

I do agree that for some kinds of testing (particularly from a bench or using a machine rest) larger group sizes can make a lot of sense.
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