3 shot groups verus 5 shot groups

[BoydAllen]

Klong,
I find your methods logical. Your reference to how magazines usually test made me smile. Have you noticed the setups that they typically use for testing? More often than not, there is a picture of some scribe sitting at what has to be a wobbly bench, shooting off of a less than optimal rest/bag setup, with nary a wind flag in sight, no eye or ear protection in evidence, all this accompanied with an explanation of how windy it was on the day that the test had to be done. ;D

 

[dcali]

7 shots is the magic number:

http://www.border-barrels.com/articles/rimfire_accuracy/group_statistics.htm

The uncomfortable truth is you need to shoot several groups to get anything meaningful out of it. Many a wive's tale has been born when folks try to interpret with too little data.

"You have some vertical - clean up your primer holes."
"Naw, there's a vertical wind out there over the berm."
"That one's got a flyer. Better weigh and sort your bullets."
"My rifle's shooting .5 MOA at 300 yards, but .75 MOA at 200 yards. Bullets must be going to sleep."
And many more...

All more often than not attributable to drawing conclusions without enough information.

 

[BoydAllen]

Tell you what...with a barrel life that may be 1,200 rounds, on a rifle that is dead dependable (full house 10.5# 6PPC, 36X scope, 2 oz. trigger, great rest and bags) shooting over flags, on an easy wind day. If there is paper between two rapidly fired shots, no amount of additional shooting is going to fix the group. It is time to make a decision and change something. Some fellows, try to make sighting corrections for shots that fall within a rifle's average group size, and talk about fliers that are really just the widest shots in the group, but with a rifle that is really accurate, you can learn a lot about tuning, rifle handling, and reading flags, because there is close to a 1 to one correspondence between input and output. With lesser rifles, and ammunition, more shots ARE required to draw useful conclusions, and the funny part is, watching someone test loads without flags, on a day where you are having to pay strict attention to them to achieve something close to what your rifle is capable of.

 

[dcali]

You have a great point, Boyd. If the first two are unacceptable, shoot no more! But if you're trying to decide between two loads, one of wich shoots .6 MOA and one that shoots .8 MOA, then a couple of three-shot (or even five-shot) groups isn't going to work.

For my high power rifle, I tend to burn up a fair amount of ammo picking a load. But as you say, there's a big difference in barrel life between a service rifle that needs to hold .75 MOA and a BR rig that needs to hold .2 or less. It's a balancing act for sure. Confidence vs. time/money/usable barrel life.