Thread: 3 shot groups are useless!

The simple method. Using the same bullet (80 ELDM) but different brass (Ammo Inc) and powder (2206h). Load 20rd at book max, some misc distance off the lands.

10 shots at 100m, 20mm. Good. 1 click left for zero. Velocity at target range (2700), SD is what it is (15 across those 10 shots. Fine)

3 shots plate centre at 400, 600, dropped one off plate edge at 800 in the wind, 2 plate centre. Done.

Nice. So this is the future as it's going to apply to me . . . . I'm going to always buy/build rifles with the barrel as the primary focus - hence I don't see too many factory rifles in my future, sure some like Lithgows, Sakos & Tikkas (occasionally) can shoot pretty well, they are still nothing like a good custom barrel like a Krieger, Bartlelin, Brux or Mullerworks etc. etc.

Originally Posted by Tentman

Nice. So this is the future as it's going to apply to me . . . . I'm going to always buy/build rifles with the barrel as the primary focus - hence I don't see too many factory rifles in my future, sure some like Lithgows, Sakos & Tikkas (occasionally) can shoot pretty well, they are still nothing like a good custom barrel like a Krieger, Bartlelin, Brux or Mullerworks etc. etc.

Yep you will definitely start on the front foot with a high quality barrel.
My bartlein barreled 6.5prc @Kiwi Greg had built for me just shoots everything brilliant and is still the most precise & accurate barrel I have fired.

The combination of good system and simple approach certainly seems to make it easy when you discard all the nonsense. Get good data quickly, without meaningless fiddling, and you're away. Load developed and tested successfully to 800m in 19 rounds, and about 2 hours all up including driving. 1 round left ready to shoot a deer even.

Originally Posted by gimp

The combination of good system and simple approach certainly seems to make it easy when you discard all the nonsense. Get good data quickly, without meaningless fiddling, and you're away. Load developed and tested successfully to 800m in 19 rounds, and about 2 hours all up including driving. 1 round left ready to shoot a deer even.

Not all bullets shoot well in some barrels.
Your load appears to be an easy one because the barrel likes the bullet.
Good data quickly could be shown with the initial 3 shot group... If it is over MOA then don't bother continuing with the current load or possibly even change bullet.

I have done some loads in my rifles that just straight shot good with the charge ladder to find pressure and I knew the load was going to be quick and easy.
Others shot good initially but then issues appeared down the track I. E. 80gr eldm in the 223, initially shot brilliant at the peak of summer but shot shit once temps cooled off.
When loads don't come easily then the "meaningless tinkering " starts but you can't tell what was meaningless or not until you either crack the good load or realise it just ain't gonna shoot good.
When you think you have a decent load then your multiple x# of shot groups come into play to gain confidence in the loads potential/ability.

Originally Posted by Roarless20

Not all bullets shoot well in some barrels.
Your load appears to be an easy one because the barrel likes the bullet.
Good data quickly could be shown with the initial 3 shot group... If it is over MOA then don't bother continuing with the current load or possibly even change bullet.
I have done some loads in my rifles that just straight shot good with the charge ladder to find pressure and I knew the load was going to be quick and easy.
Others shot good initially but then issues appeared down the track I. E. 80gr eldm in the 223, initially shot brilliant at the peak of summer but shot shit once temps cooled off.
When loads don't come easily then the "meaningless tinkering " starts but you can't tell what was meaningless or not until you either crack the good load or realise it just ain't gonna shoot good.
When you think you have a decent load then your multiple x# of shot groups come into play to gain confidence in the loads potential/ability.

You could indeed do this with a 3 shot group - however it doesn't seem like a very sensible approach to me - 3 shots would only tell you that the load is not acceptable in some circumstances - there is just as much chance that the 3 shots would group acceptably, and lead to you chasing your tail.

A 10 shot test group tells you - does this powder/brass/bullet combination have acceptable precision in my system? This can be discovered, and a reasonable velocity average developed, in one range session quickly and efficiently. This does require that you start with a high quality system and good components. Of course, a poor system and components will simply produce worse results, you'll still understand that equally with this approach.

a "ladder" of various 3 shot groups would tell me nothing more, and in fact, significantly less.

I don't believe charge weight has a really meaningful relationship to precision, in my rifle - and probably in many (most) others - when you actually gather a meaningful amount of data at each charge weight, groups are functionally identical.


Same for seating depth.



There are layers of accepted theory that we are challenging here


I would be interested to see the data you have regarding your .223 with the 80gr ELDM.

What is the theoretical explanation for it not shooting well between seasons? Is the "change in precision" actually supported by data?

Edit ok I see it's this

Originally Posted by Roarless20

I initially had them shoot great in my 1:8 tikka @2920fps. But that was in hot weather and only one batch of pills which measured 0.020" shorter than the next batch lot I got. It was erratic as after the temperatures cooled off.
The 80gr are too long to stabilise in 1:8twist at that speed or less. If you change temp and barometric pressure in your ballistic app you can see the stability calc go up and down accordingly.
I ground 80% of the red tips off some as a test and they shot good again but their BC was degraded down to about G1 0.290!

Which is an interesting phenomenon, but not really load development related - nothing you could do differently in the initial process - or afterward to correct - and very strange, as it indicates that perhaps Tikka twist rates are not quite a true 1:8

Originally Posted by Kiwi Greg

So what I'm getting at here is my light rifle & arguably my heavy rifle (which normally shoots better) are genuine 0.1 moa 5 shot rifles but only in the right conditions without an idiot driving them

I've not felt the need to post further on this thread, what with Gimp holding the corner so well on his own. However, and perhaps surprisingly, I find that it is Greg's post that I keep coming back to as the one that is going to finally prompt me to hit the keyboard again, as being in need of some clarification in my view.

The general theme of the thread is about what constitutes statistical significance, and what statements on performance can fairly be made about a rifle from a given set of target data.

The conclusion that Greg’s two 6PPC benchrest rifles are both 0.1moa performers CANNOT be drawn from the targets he has posted. I hope that that is clear, because I didn’t think that the way it was presented, and in the context of the other posts, that it necessarily was?

Whereas other members have posted sets of targets and asked the question “what is the capability of this rifle when these targets are taken in isolation”, I wanted to point out that in Greg’s post the targets are not to be taken in isolation. He is drawing on a large amount of prior knowledge of his rifles that we are not being made privy to in making the statement that both these rifles are “genuine 0.1moa 5-shot rifles”.

He is in the very unusual position of having access to something of a performance benchmark in these two rifles and where groups that exceed a previously established baseline sizing can then reasonably be attributed to causes other than those relating to the rifles alone.

It becomes a demonstration that when we are approaching an assessment of a rifle from the opposite direction — where we have little knowledge of the rifle’s actual capability and are hoping to interpret a set of targets to draw our conclusions — that amongst other factors, the influence of the shooter and environment will be contributors to the group size and mean POI. While we of course accept this, such separation is rarely able to be demonstrated as it has been here.

Originally Posted by Puffin

I've not felt the need to post further on this thread, what with Gimp holding the corner so well on his own. However, and perhaps surprisingly, I find that it is Greg's post that I keep coming back to as the one that is going to finally prompt me to hit the keyboard again, as being in need of some clarification in my view.

The general theme of the thread is about what constitutes statistical significance, and what statements on performance can fairly be made about a rifle from a given set of target data.

The conclusion that Greg’s two 6PPC benchrest rifles are both 0.1moa performers CANNOT be drawn from the targets he has posted. I hope that that is clear, because I didn’t think that the way it was presented, and in the context of the other posts, that it necessarily was?

Whereas other members have posted sets of targets and asked the question “what is the capability of this rifle when these targets are taken in isolation”, I wanted to point out that in Greg’s post the targets are not to be taken in isolation. He is drawing on a large amount of prior knowledge of his rifles that we are not being made privy to in making the statement that both these rifles are “genuine 0.1moa 5-shot rifles”.

He is in the very unusual position of having access to something of a performance benchmark in these two rifles and where groups that exceed a previously established baseline sizing can then reasonably be attributed to causes other than those relating to the rifles alone.

It becomes a demonstration that when we are approaching an assessment of a rifle from the opposite direction — where we have little knowledge of the rifle’s actual capability and are hoping to interpret a set of targets to draw our conclusions — that amongst other factors, the influence of the shooter and environment will be contributors to the group size and mean POI. While we of course accept this, such separation is rarely able to be demonstrated as it has been here.

It is interesting and I have also been thinking about it.

The question that arises is "what is meant by genuine 0.1moa 5-shot rifles ?"

The definition of that is rather important.

Is it -

- Rifles that will occasionally shoot a 0.1moa 5 shot group, as part of the natural variation in group sizes (but with an average group size larger than that)

OR

- Rifles that produce, on average, 0.1moa 5 shot groups (meaning that the natural variation results in both larger and smaller groups from time to time)

OR

- Rifles that can be characterised as having sufficient precision to produce a high hit probability on a 0.1MOA target (disregarding the other aspects of hit probability)


Of course, the rifle itself is not the entire picture, the shooter error is part of it.

what would be interesting would be to see the difference in average group size (or mean radius of all shots in those composite groups) between Greg vs, in his words - someone not an idiot driving them. (not having a go Greg !)


It is interesting to observe that an average 5 shot group size for a benchrest rifle being shot by an expert is over .25MOA. Makes the idea of .25MOA hunting rifles seem vanishingly unlikely in reality.

It would also be interesting to plot all shots and understand the overall actual precision - as the average of multiple groups is less informative than one single large group

Originally Posted by gimp

It is interesting and I have also been thinking about it.

The question that arises is "what is meant by genuine 0.1moa 5-shot rifles ?"

The definition of that is rather important.

Is it -

- Rifles that will occasionally shoot a 0.1moa 5 shot group, as part of the natural variation in group sizes (but with an average group size larger than that)

OR

- Rifles that produce, on average, 0.1moa 5 shot groups (meaning that the natural variation results in both larger and smaller groups from time to time)

OR

- Rifles that can be characterised as having sufficient precision to produce a high hit probability on a 0.1MOA target (disregarding the other aspects of hit probability)


Of course, the rifle itself is not the entire picture, the shooter error is part of it.

what would be interesting would be to see the difference in average group size (or mean radius of all shots in those composite groups) between Greg vs, in his words - someone not an idiot driving them. (not having a go Greg !)


It is interesting to observe that an average 5 shot group size for a benchrest rifle being shot by an expert is over .25MOA. Makes the idea of .25MOA hunting rifles seem vanishingly unlikely in reality.

It would also be interesting to plot all shots and understand the overall actual precision - as the average of multiple groups is less informative than one single large group

Haha - even .75 is nearly vanishing rare Id say.

But even experts get sucked in. I just watched Desert Precisions latest video, normally Kenny us pretty sound. But here are two consecutive 10 shot groups with a small but significant POI shift between them. Oh dear! And the irony, he's looking at 22 Ammo SDs with only 10 shot sample sizes

Originally Posted by Tentman

Haha - even .75 is nearly vanishing rare Id say.

The single groups posted recently with some larger sample sizes (10 rd) on this forum indicate that you're right - considering that you should expect about 30% variation in group size up/down from the average size of a 10rd group... and the "actual" precision is the high end, and better represented with 20-30rd of data

Been some really good groups that people have posted, but all around the .7-1.5moa for 10rd.

Man reading the last three posts. It comes to mind.... If a fella said he could " get it up instantly" you lot would wheel in Susan Boyle just to prove him wrong. Federal blue box factory ammunition has for many years been considered a good indication if not benchmark to see if rifle is accurate. Maybe because it's very consistent and has a seating depth that suits all but most finicky rifles.

It might just be so that Blue box is pretty good. If say the machinery it run on has been replaced, or s new guy has super tuned up the old gear . . . or several other possiblilities!

Two 10 shot groups using thermal clipon on a tika 308.Ammo factory Hornady White tail 165gr sp.Took about 2hrs,barrel just had some light hopps patchs thru it.
1st group of ten.
Purple,3 shots.High n wild.10 minute cool down.
Orange,2 shots touching then flyer,10 min cool down.
Reds,2shots touching then flyers,10 min cool down.

After some adjustment with thermal,1clk right,1clk down.
Blue gave nice 3 shot group.
Then I had to really get my eyes right for target,blurry.Got make sure I'm on vertical.
Green 3 shots gave bull eyes a look,good.
Red i aimed tad lower,got 3 below bull.My eyes on thermal target getting blurry again.On the second set of 10 shots the tika seemed to get groups better.
Il take the green group hunting any day.
Thermal target shooting a lot harder than day target shooting any day.

Thats little piece of tin foil was getting blurry thru thermal tho.

1.2 inch for that top group is outstaying for a clip on and damned good for anything.

Thank you for posting, Trout. The first 10 is a nice round shape as you'd expect and probably more closely represents the true precision of the system vs the smaller groups just randomly sampling from within it, acknowledging that the aiming error in a system with a clip on thermal is probably substantially higher than a good daytime optic.

2nd 10rd obviously also represents the overall precision better than sub groups, with vertical distortion due to aiming shift mentioned