Thread: 3 shot groups are useless!

Originally Posted by gimp

You could refer to it as a "half MOA" rifle

Thanks - will do...

Originally Posted by earplay

Thanks - will do...

Why not a 0.15MOA rifle....

Originally Posted by gimp

Why not a 0.15MOA rifle....

That's an idea. I just need to do it in both morning and afternoon to call it "all day".

Ok you finally broke me down enough to put together two 5 shot groups into a 10 shot.
From my Kimber 6mmCM which i barreled (Truefite barrel - re-tenoned from a tikka) and also hand built the carbon stock on.

I checked zero after a fall with the rifle recently & I had a group i shot after sharpening up the crown (looks like i forgot to adjust zero after that one) which i have overlaid.





Very good for such a lightweight rifle shot over some handmade sand bags where every breath or muscle movement alters the POA. Definitely shows you if your technique is poor when shooting like this.

In a nod to his thread and how I can improve my group sizes, Ive recently gone to 2 shot groups

0.25 MOA groups now the norm

Originally Posted by Billo

In a nod to his thread and how I can improve my group sizes, Ive recently gone to 2 shot groups

0.25 MOA groups now the norm

One shot should get that down further.

Originally Posted by Tahr

One shot should get that down further.

Was that comment really kneeded?

Originally Posted by Ross Nolan

Was that comment really kneeded?

Bread is kneaded.

Originally Posted by Tahr

Bread is kneaded.

And your knee was very nearly toast.

A toast too Knees, and bread. You'll Kneed both.

Originally Posted by gimp

I actually want everyone else to shoot worse and less successfully.


Right, enough about my many and various personal shortcomings, let's look at some 3-shot groups. Last week.


This is a pretty normal data set. Standard T3 7mm08 with a handload, leupold scope, expert shooter (much better qualifications than me), off the bench at 105m. No wind to speak of. Getting a zero for <300m hunting.


Whole target:
Attachment 286283


First 3 shot group - 0.87 MOA - adjusted up 1.0MOA and right 1.5MOA after this.
Attachment 286284

Second 3 shot group - 1.08MOA - adjusted up 0.5MOA and right 0.5MOA after this
Attachment 286285

Third 3 shot group - probably good enough for the purpose.
Attachment 286286

We can use the data from this exercise to undertake some analysis. I adjusted all the shot for their position to have a common point of reference - translating groups 1 and 2 by the total adjustments to overlay them on group 3.

This analysis does make the assumption that the scope is functional. If the scope has a relatively massive error, like 10%, then the analysis is still broadly correct. If the scope is total junk and just does not track at all, then the analysis might be questionable.

Here's what we get.

Precision:

The rifle shot 3x 3 shot groups averaging 1.09 MOA. Pretty good. The combined group of all 9 shots is 71.5mm, or 2.3 MOA.
The mean radius of the 9-shot sample from a common point of reference is 19.8mm with an SD of 11.9mm (+- 9.1mm @ 95% CI)
This mean radius means that the total dispersion of the rifle is around 82.3mm (2.7MOA). (44 - 120mm @ 95% CI)


Accuracy:
The MPOI of all 9 shots is at +1.8mm (+- 18.8mm @ 95% CI) for windage, and +2.8mm (+- 15.3mm @ 95% CI) for elevation.
We can be highly confident that it's zeroed within 2 clicks in each direction. That's good for the intended purpose. We cannot be more confident than that.

The mean POI of group 1 (adjusted) is 17mm right of the 9-shot MPOI, and 13mm high.
The mean POI of group 2 (adjusted) is 13mm left of the 9-shot MPOI, and 13mm low.
The mean POI of group 3 (adjusted) is 3mm left of the 9-shot MPOI, and almost pefect for elevation.

So one of the 3-rnd groups accurately matches the best estimate we have of the true MPOI within 2 clicks in each direction, the other 2 are about 2 clicks off in both directions.


This is a handy example of getting a zero that's suitable for hunting at conventional ranges using 3 shot groups with a rifle of pretty average precision. Very normal situation. We can pool all the data and have an understanding of exactly how confident in it we can be, and for what.


You'll notice, @Micky Duck, that 2 of the 3x 3-shot group MPOIs are far more than 20mm apart - you indicated that you've never seen this in 50 years, but this is not unusual with systems with average precision and small samples.

Thank you, Gimp, for your patience and endurance in leading an exploration into the application of statistics to better understand the performance/precision of a rifle and shooter. This thread along with the Hornady podcasts have been motivation for me to challenge my approach to developing handloads and zeroing my rifles. I followed the convention of relying on three shot groups for centre fire rifles as the basis of developing loads and zeroing my firearms. My experience since moving to ten shot groups as a part of this process has aligned with the statements you have made. I have at times in the past achieved my share of stellar three shot groups of which to be proud to then subsequently be confounded by that which was much more pedestrian using the same loads. I have also had experiences where a zero established at 100metres resulted in points of impact at 300m which seemed inexplicable when taking account of ballistic tables and chronograph data. Ten shot groups have clarified this for me.

I have found it quite liberating and insightful . It seems for an initial investment of ten shots first up can save one disappearing down a rabbit hole chasing your tail with confounding results. It also has helped me understand and accept the limitations of my equipment and operator and concentrate on the importance of marksmanship.

So thank you.

I would be interested in your comments in relation to the example you have provided with the 7mm 08. The precision of this firearm more aligns with my experience. (I cannot approach the extraordinary precision demonstrated in the images submitted by some of you highly skilled marksman which are seriously impressive for a "plumber" like me). Specifically, with a rifle that shoots a ten shot group around the 2 MOA with a mean radius of around 0.6 - 0.7 MOA, what would you consider to be the maximum range for hunting deer size targets?

R

Originally Posted by RHG

Thank you, Gimp, for your patience and endurance in leading an exploration into the application of statistics to better understand the performance/precision of a rifle and shooter. This thread along with the Hornady podcasts have been motivation for me to challenge my approach to developing handloads and zeroing my rifles. I followed the convention of relying on three shot groups for centre fire rifles as the basis of developing loads and zeroing my firearms. My experience since moving to ten shot groups as a part of this process has aligned with the statements you have made. I have at times in the past achieved my share of stellar three shot groups of which to be proud to then subsequently be confounded by that which was much more pedestrian using the same loads. I have also had experiences where a zero established at 100metres resulted in points of impact at 300m which seemed inexplicable when taking account of ballistic tables and chronograph data. Ten shot groups have clarified this for me.

I have found it quite liberating and insightful . It seems for an initial investment of ten shots first up can save one disappearing down a rabbit hole chasing your tail with confounding results. It also has helped me understand and accept the limitations of my equipment and operator and concentrate on the importance of marksmanship.

So thank you.

I would be interested in your comments in relation to the example you have provided with the 7mm 08. The precision of this firearm more aligns with my experience. (I cannot approach the extraordinary precision demonstrated in the images submitted by some of you highly skilled marksman which are seriously impressive for a "plumber" like me). Specifically, with a rifle that shoots a ten shot group around the 2 MOA with a mean radius of around 0.6 - 0.7 MOA, what would you consider to be the maximum range for hunting deer size targets?

R

Thank you for the positive feedback, it's nice to know that my efforts have helped a few people



A rifle system that shoots a 10-round group of around 2MOA with a mean radius 0.6-0.7MOA is highly effective out to 400 metres (high mechanical hit probability) on goat/deer-sized animals. This is the sort of system most hunters using off-the-shelf rifles and factory ammo are using, whether they realise it or not. The shooter making egregious mistakes is the biggest source of error at these ranges.

Originally Posted by gimp

The shooter making egregious mistakes is the biggest source of error at these ranges.

I think that's a good point that gets overlooked in these discussions sometimes. It would be interesting to compare groups shot from a bench to those same systems/groups shot in the field. I suspect it'd be a lot more variance than any reloading variable. I'd hate to see a 'group' of mine at 300m shot from the top of a leatherwood bush...(with a small dose of adrenaline).

Many thanks for your response, Gimp. That is brilliant and greatly advances my understanding.

I have been tooling around with four different firearms with (by comparison to the examples displayed here) mostly underwhelming outcomes.

First is a 3006 built from a Zastava M98 action who knows when but probably not all that long ago, rebarreled with a Swann 25" barrel that has been shamelessly purloined by my daughter's partner. He is keen to get into a bit of long range shooting at targets and to be able to shoot at our fallow out to around up to ~ 450 metres. This rifle showed encouraging signs with dirty old 150 gr PPU Sp 150 (three shot groups consistently around just under 1 MOA at 100 metres). But, exposed to the rigours of the ten shot test, the best hand load (49.5 gr AR 2208 168 gr Hornady ELD M) outcome has been a lacklustre at 2.01" at 100 m (1.76 MOA) with a mean radius 0.66 MOA)

My daughter's partner has been doing rather well hitting steel at 500m with the 150 gr PPU out of tis rifle which is encouraging.

Second is a dirty old 1970's vintage Parker Hale M98 Santa Barbara action in 308. A previous owner removed the iron sights and docked the barrel to 18". I have dicked about rebedding it twice, polishing the action, worked on the trigger and restored the stock. Once again, the precision with 150 gr SP's (Speer Hotcor/Hornady interlock) was of the order of 1 - 1.3 MOA at 100 with three shot groups, and surprisingly extraordinary with 130 gr Hornady SP's with average around 0.80 MOA and some real bug holes amongst them.

Put something more aero dynamic in the case (Speer 165 gr BTSP / 42.5 gr AR2206H) and expose it to the challenge of 10 shots and the outcome has been as you have predicted - 1.80 MOA at 100 with a M/R of 0.67 MOA.

Thirdly, I submit my hunting rifle, a POS Marlin Xs7 in 7mm08 (yes, but it is my piece of shit...). This has had way to much energy spent on it trying to make t shoot and overcome the design and engineering faults that are inherent in this cheap production rifle. It has after much work proved to be seemingly rather precise with 3 shot group averages for 110 grain Speer, 120 gr Sierra Prohunter and 139 gr Hornady interlock around 0.80" at 100m, 1.5" for Speer 145 gr and 1.2" for Speer 160 BTSP. Some absolute bughole flukes with the 120's and 139 gr of 0.3" - 0.4" (three shot).

A ten shot group with 160 gr Speer BTSP at 100m, however, returned an ES of 1.84 MOA and MR of 0.56 MOA.

A bit of a theme here.

Finally, a stock standard Tikka T3 Lite 223 which has had very little use (about 140 round count on account of there being nothing to shoot at here with it other than 50,000, 000 starving wallabies so poor that even the dogs won't eat them). This has had a few factory rounds through it to recover brass and then a load thrown together using 19 cc tipper of AR 2208 supporting cheap as chips Nosler Shots 55 gr HP's. This load has proven consistently precise with lots of sub 0.5 MOA three shot groups at 100m.

A ten shot group using the above recipe returned an ES of 1.25 MOA @ 100m with MR of 0.36 MOA.

I have bored you with this narrative to provide an example of how things spin at the beer and pork pie end of the spectrum.

I suspect the way forward from here with the hunting rifles is to run the loads described for the ten shot groups across the chronograph, run the numbers thus sourced through the ballistics table, fine tune the zero then validate POI's on out to the extreme hunting distances. Load up some more then belt the gongs at distance to improve confidence and technique and have at it on Bambi.

Once again, thank you for your assistance. Greatly appreciated

R

I have to ask the realy stupid question . How is it anyone believes any of this , and yet at no time has anyone actualy provided any evidence as to how this is relavant ? and not just total and utter bulshit???????????????????