Thread: Getting good data from 3 shot groups

Originally Posted by Hahn

I wanted to try your data out and get your thoughts. I plotted them as you shot them into three 3-shot and two 2-shot groups from left to right. Assumed 100yard and 1 inch diamond.
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Overlaying the aggregates:
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Then centering on aimpoint:
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My first thought was I wanted centered on aim point for small data sets such as 3 shot groups, as this should negate the lack of true MPI from lack of individual group data. Then I figured if this was a long term analysis with many more groups added then centered of MPI would probably give the same result eventually but wouldn't be affected by zero changes.

Ohh I see you round robined it so my groups are out, however my aggregate treats them as individual shots. As to your original purpose, 13 shots to zero: one click down

Hey very interesting analysis, I'm still thinking your graphs through (old brains are slow and all that)!

Originally Posted by Tentman

You're assuming I'm appealing to logic, I'm not, this is about belief!

It seems to me by shooting round robin, you are more testing shooting consistency......well that's my take on it. Interesting all the same.
I have moved to shooting a single larger sample for zeroing myself minimum 10 shots but often more (cue the component waste police )
I'm probably not as far down the rabbit hole as you guys but it sure has simplified my load development process.

I agree with gimp that in general 3x 3 shot groups are no more informative than 1x 9 shot group.

However, as noted, round robinning at different targets introduces some possibility of shooter position change impairing precision. The same applies in smallbore shooting, as woods223 explained. I would never adjust after a single bad shot but look back over 4 or 5 shots abd if all on the same side then make a cautious adjustment, presuming there was a positiin/ clothing change or else a small wandering zero process going on in the rifle. Sort of an intuitive Westgard Rule approach.

When the apparent MPI error is less than the group size you need to be quite cautious in making adjustments. MPI can move a little from one session to another. Not so much between round robin shots in one session.

Good philosophical exercise, tentman, but look for the logic behind your observations.

If you fire a 5 shot group and the MPI is 1cm out it can look really awful but in the greater scheme of things its quite tolerable and if you chase a centimetre on several occasions it usually just adds several centimetres to your overall inaccuracy.

It funny how many people comment on these sorts of threads but don't post up pictures of their groups and zeros, I recall Gimp, Hahn and woods233 have but not too many others . . . . Quite a lot of armchair experts I suspect . . . .

What is the question that you are trying to answer here mate?

Can you still get useful info from a 3rd group? Yes. But that info is not as accurate as what you'd get from 3x3 or 1x10.

Is it accurate enough? If you are trying to get the mechanical zero to within one click with a high degree of confidence, potentially. It's relative to the precision of the rifle... I wouldn't have made a different adjustment based on any one of those 3rd groups you've shot there... But if it was Zedrex's 243 then you could end up chasing your tail.

Here's a 10rd group I shot the other day. Based on this, I'd probably come 3 clicks left, plug a 1.5" high offset into AB/4DOF and call it good. It's at the point where shooting more rounds is not likely to refine the result a useful amount further. I am rounding to the nearest 1/4 MOA to make my adjustments anyway, since that's the smallest amount I can dial the scope.

[QUOTE=Pommy;1756502] But if it was Zedrex's 243 then you could end up chasing your tail.

QUOTE]

Cheeky git, my 243 is finally shooting well now that it's being fed Nosler BT's!
8 for 7 at 200m on a 6" gong the other day and now I've got the chrony I'll be confirming or otherwise my calculated velocity of 3250 fps....mind you that calculation came from a 3 shot group so no promises made just yet!

Originally Posted by Tentman

It funny how many people comment on these sorts of threads but don't post up pictures of their groups and zeros, I recall Gimp, Hahn and woods233 have but not too many others . . . . Quite a lot of armchair experts I suspect . . . .

https://youtu.be/aTRSmjUfYrs?si=HeMvaJb_rPVFA86I


To be fair, I thought your initial post was humour. A 3 shot group where you fire 13 shots to get the info.

Originally Posted by Tentman

It funny how many people comment on these sorts of threads but don't post up pictures of their groups and zeros, I recall Gimp, Hahn and woods233 have but not too many others . . . . Quite a lot of armchair experts I suspect . . . .

It's fun, isn't it

Seriously now. You can't bully or force people into participation in the way you want.

In reality the only option is to decide for yourself, the value you place in other individuals opinions.

This whole topic, Its two seperate issues that as I see it, dont have a meeting point. Either you are focussed on extreme precision, for target shooting or long range shooting of animals. In which case even before this thread, you would likely have been using groups larger than 3 shots to determine your accuracy and precision.

Or

You are an ordinary hunter who has the luxury of making their decisions on less information/ choosing other actions to take primary position.

I literally haven't shot any groups since load development in October, I've already posted those pics so didn't see any relevance in posting them again.
Will need to get some trigger time in before working out a load for the 7prc but I've been out of action for a while with a crook back, no real progress with the back but I'm seeing a specialist in the new year.
For what its worth I agree with the concept of larger sample sizes for load development and zero setting, I do think your post referencing "armchair experts" is a little antagonistic even if unintentionally, your better than that Foster.
Maybe I'm just being precious, pain effects us all differently

Originally Posted by Tentman

Hey very interesting analysis, I'm still thinking your graphs through (old brains are slow and all that)!

So thinking about your test... With a round robin it is 13 single shots combined into 3 shot aggregate groups? So really you have come up with a way to analyse multiple single shots. The physical version of what I did digitally with your 13.

I'm just a little confused, are 3 shot groups useless? Or can you get good data from 3 shot groups?

Originally Posted by Hahn

So thinking about your test... With a round robin it is 13 single shots combined into 3 shot aggregate groups? So really you have come up with a way to analyse multiple single shots. The physical version of what I did digitally with your 13.

Bingo, that's the nub of it. It's much more hunting related than most people would realise. All this "you're changing position" is correct, but that's what every hunting shot is anyway. It might help some people, then there are those whose thinking is challenged (so I'm taking the piss) and everyone continues on their merry way, good on them.

I might be one of those. I dont particularly feel challenged. Im struggling to see the value in this approach and maybe you could explain it more.

From where I sit it looks more like a test of 10+ individual shots and shooter precision. Of which, 7.7% failed for an unknown reason, that would take more series of the same test to work out if thats statistically reliable, or not.

Whats the goal? If it's rifle precision then why introduce more potential for human error than necessary? If its the shooters precision, then why use a rifle with a history of poor precision?