Myth Busting - 50 round shot groups at 25 yards - Extreme 9mm accuracy testing

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LiveLife

LiveLife

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With my retirement date finally set (I chose 5th of July so I can celebrate my independence from work every year with 4th of July :thumbup::D), I have taken some time to reflect over work that's been done for accuracy testing as outlined in this post - https://www.thehighroad.org/index.p...-and-discussions.778197/page-10#post-10966692

After reviewing many threads and posts by more experienced THR members on accuracy testing, especially when they posted that sample size is too small to make a definite determination (Yes Walkalong, sample size must be large enough to matter ;)), I increased my shot group size from 5 rounds to 10 rounds.

Well, after doing some extensive sorting and range testing various 22LR ammunition, I am beginning to believe even 10 round groups may not provide all the information as to true accuracy (jmorris and Bart. B, you were right :D).

Shooting 20, 30, 40 and 50 round groups opened up the group size with "occasional flyers" becoming more regular :eek: - https://www.thehighroad.org/index.p...weight-and-rim-thickness-for-accuracy.850634/

As reference, this article conducted 50 round (entire box of ammo) shot group testing with Ransom Rest at 25 yards - https://www.ssusa.org/articles/2019/1/18/38-different-9mm-loads

Compiled 50 round group sizes shown in this table is quite interesting (Not what I expected) and I will start doing 20-50 round shot group testing at 25 yards in the future for evaluating accuracy of loads - https://d2mhjaozymokej.cloudfront.net/media/1540004/table-1-extreme.jpg
 
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bds said:
With my retirement date finally set (I chose 5th of July so I can celebrate my independence from work every year with 4th of July :thumbup::D),
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Well done and great retirement pick. I guess you realize that you are going to busier than you've ever been but its grand! All the best! :thumbup:
 
Thank you. It's still a little hectic getting all the retirement paperwork in order and finalizing my retirement plan/routine sorted out.

While wife's growing "honey do list" takes higher priority, she has given me the green light to pursue shooting/reloading and restoration of two Starcraft fishing boats as my initial retirement projects to "take breaks" from her projects. :D (Believe me, she has some lofty retirement projects for me to pursue)

It will be nice to not have to rush range testing or limit sample size to 10 shot groups as I verify some of myth busting threads' range tests.
 
Congrats on your upcoming retirement.

I think the ever increasing size of shot group testing is an offshoot of reporting results in the interwebs, where no one believes anything is true. Soon a 100 shot group won't be enough.
 
Enjoy your retirement. And say good bye to your free time. There is always something that will fill any gap you may have.

I'm finishing up on my boat restoration/rebuild within a couple more weeks. Polishing the hull now, wax, then will be ready to flip it over and put the top cap back on. Then I get to install carpet, some gel coat patch on cap, wiring, drains .... The list of things to do seam to never get any shorter.
 
Congratulations bds! I guess some people really do get to before its too late to enjoy it!

69 and a half and no retirement in sight....that's the trouble with working for yourself......

I don't worry about large groups....or small ones.....guess I'm not a "real" handloader.....if it shoots as good or better than factory, I'm content. I tried to get interested in swimming in the deep end, but don't think its going to happen. For me match play isn't play at all. ;)
 
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GW Staar said:
Congratulations bds! I guess some people really do get to before its too late to enjoy it!

69 and a half and no retirement in sight....that's the trouble with working for yourself......

I don't worry about large groups....or small ones.....guess I'm not a "real" handloader.....if it shoots as good or better that factory, I'm content. I tried to get interested in swimming in the deep end, but don't think its going to happen. For me match play isn't play at all. ;)
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I was self employed for quite a while until I realized my boss was an ***hole and a slave driver........ ;)
FWIW I retired 8 years ago at 55
 
Congrats on your retirement. I was forced to quit at 61 due to medical conditions and unfortunately all saving were eaten up by medical bill by then. Fortunately the wife is a bit younger and is still working. Hopefully you won't experience this.

On good days I get a lot done, bad days not so much. Wish I could find a place to shoot cheaply.

Since I do not have access to a chono I just do group testing and try to get more than one session to compare a good day to a mediocre day. With groups of 25 to 50 rounds.
 
Thank you all for the retirement congrats. Was planning to retire after 25 years of state government "enslavement" but decided to call it quits after 24 years due to unforeseen medical issues (choose your parents carefully). Working with Physical Therapy what I can do and cannot do and being smart about not pushing my body too hard with plenty of rest days is helping.

Yes, looking at the long and growing "honey do list" from wife, I am starting to get overwhelmed ... starting with doubling the size of master bathroom with fabricating all custom cabinets and separate shower/jacuzzi tub while doing all tile work ... FUN.

Then tearing down existing porch and building a full house length enclosed patio with full wrap around window walls ... more FUN.

And building a new 36'x12' enclosed patio off master bedroom through a new french door ... FUN FUN.

And a new 3 car garage with attached workshop ... FUN FUN FUN.

And so on, and so on and so on ... :eek:

OK, back to OP. :D
 
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GW Staar said:
I don't worry about large groups....or small ones.....guess I'm not a "real" handloader.....if it shoots as good or better that factory, I'm content.
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kidneyboy said:
I think the ever increasing size of shot group testing is an offshoot of reporting results in the interwebs, where no one believes anything is true. Soon a 100 shot group won't be enough.
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Anyone who has followed my various myth busting threads will see that I have worked to isolate reloading variables and better standardize my testing methods - https://www.thehighroad.org/index.p...-and-discussions.778197/page-10#post-10966692

I have done initial simple optical machine pistol rest build prototyping for 25 yard testing and now working on hybrid recoiling optical machine pistol/carbine rest to conduct 25/50 yard testing (Expect new thread on machine rest build).

I am glad we have done various myth busting threads, especially with great input from many THR members as moving forward, verifying range tests will be more objective and definitive due to already isolated reloading variables myth confirming/busting that have been done.

But with that said, myth busting 50 round 25 yard testing is to satisfy some THR members (obviously argued with good fundamental basis and intentions) who post that sample size matters and I do want to test some accurate loads at 20/30/40/50 round count to do some verification.

I do not believe 100 round group testing will be necessary as I hope the new hybrid machine rest testing will better verify group size without human factor to better show accuracy trends from 5/10 round groups all the way to 50 round groups.
 
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50 round shot groups at 25 yards.......
To me, that's two rounds of handicap Trap.
I use three for sighting in, five for load development, ten for zero testing sometimes, but 50? A whole box of ammo used for just testing? More data than I need.

Congrats on retiring!
 
Thank you.

Keep in mind that we won't simply "jump" right to 50 round groups.

My plan is to reshoot known accurate reference loads and new powder loads like IMR Target, Sport Pistol, etc. starting with 10 round groups but from the hybrid machine rest and work our way up 20, 30, 40 then 50 rounds to verify the accuracy trends.

Theory is, if hybrid machine rest indeed remove human factor and identify accurate loads with 10 round groups, then results should verify with 20/30/40/50 round groups.

And we still have to myth bust primer consistency and I have plenty of Winchester, S&B and PMC SP primers to see which primer produces smallest groups.
 
bds said:
Theory is, if hybrid machine rest indeed remove human factor and identify accurate loads with 10 round groups, then results should verify with 20/30/40/50 round groups.
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How will you assess if your hybrid machine rest removes human factors? The only way I can think of is to shoot the same gun and ammo under 2 conditions; 1) with your hybrid machine rest (that appears to still have a human factor?), and compare it to 2) a strict machine rest such as a Ransom Rest or barrel fixture where there are NO human factors at play.

And how will you assess if a 10 round group identifies accurate loads? Won't you have to see what the 50-shot groups are before you can make that assessment?

You were correct previously to say that a 10-shot group is just a subset of a 50-shot group. And there is no way to know beforehand if the 10-shot group predicts the 50-shot group unless you already have the 50-shot group.

I've referenced another link in that past that shows that there can be a 2.8 times difference in 15-shot group size when shooting the same ammo from a Ransom Rest (see link below). That's why there is no way to predict that a 10-shot group is going to tell you what the final 50-shot might be. You have to shoot the 50-shot group first. I'm not trying to discourage you, but simply want to point out what might not be obvious until you really understand what happens during accuracy testing.

https://americanhandgunner.com/handguns/exclusive-consistent-velocity-accuracy/

I'm not saying that we always have to shoot 50-shot groups. Just understand that however many shots you have in your group, it has limited predicting power. Even 50-shot groups might not do a very good job of predicting a 500-shot group.
 
fxvr5 said:
How will you assess if your hybrid machine rest removes human factors? The only way I can think of is to shoot the same gun and ammo under 2 conditions; 1) with your hybrid machine rest (that appears to still have a human factor?), and compare it to 2) a strict machine rest such as a Ransom Rest or barrel fixture where there are NO human factors at play.
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OK, let's stop right there.

I wanted a machine rest to use with both pistols and carbines but will have budgetary constraints of monthly retirement pension. So I gotta make due with DIY option but I can weld and work with wood.

I will use a hybrid optical machine rest built to accommodate both pistols and carbines after it's tested to be consistent enough at 25 yards for pistols and 50 yards for carbines satisfying "my" accuracy standards. This will be the best "I" can do. If members desire something better, they would need to obtain better equipment and a new thread.

Goal will be to show "comparative" group size as I have done in my previous threads/range tests.

It will be an "unscientific" testing typical of online gun forums which happens to be posted on THR. If you want a scientific laboratory standard testing, how about doing it yourself?
 
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bds said:
If you want a scientific laboratory standard testing, how about doing it yourself?
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Done. I have a Ransom Rest. And because I have experience with it, I'm trying to pass along a little wisdom based on that experience.

As long as you are aware of the limitations of your method, you're ahead of the game. The problem I see is that some people over-interpret their results, because they don't understand that their method limits how far they can interpret their results.

It's the same thing in science. The interpretation of the results are limited by the method used to get the data.
 
fxvr5 said:
How will you assess if your hybrid machine rest removes human factors? The only way I can think of is to shoot the same gun and ammo under 2 conditions; 1) with your hybrid machine rest (that appears to still have a human factor?), and compare it to 2) a strict machine rest such as a Ransom Rest or barrel fixture where there are NO human factors at play.

And how will you assess if a 10 round group identifies accurate loads? Won't you have to see what the 50-shot groups are before you can make that assessment?

You were correct previously to say that a 10-shot group is just a subset of a 50-shot group. And there is no way to know beforehand if the 10-shot group predicts the 50-shot group unless you already have the 50-shot group.

I've referenced another link in that past that shows that there can be a 2.8 times difference in 15-shot group size when shooting the same ammo from a Ransom Rest (see link below). That's why there is no way to predict that a 10-shot group is going to tell you what the final 50-shot might be. You have to shoot the 50-shot group first. I'm not trying to discourage you, but simply want to point out what might not be obvious until you really understand what happens during accuracy testing.

https://americanhandgunner.com/handguns/exclusive-consistent-velocity-accuracy/

I'm not saying that we always have to shoot 50-shot groups. Just understand that however many shots you have in your group, it has limited predicting power. Even 50-shot groups might not do a very good job of predicting a 500-shot group.
Click to expand...

This is why the 100 shot group will be next. 50 shots is just a subset of 100 shots. 100 a subset of 500........

However, I am looking forward to your testing bds.
 
Congratulations on your retirement!!! You’ll be joining the rest of us that think we’re busier now then when we worked, but enjoying it more!

I’m looking forward to the results, and would be curious to know how much accuracy and precision is affected by barrel temp and cleanliness.
 
Grid off your target and record the impact point for each shot as a two number position with one number being the horizontal position and the other the vertical position, both relative to the impact point.

After each shot, calculate the mean and variance for both the horizontal and vertical data sets. When the means and variances for both the horizontal and vertical data sets stabilize (stop changing significantly with each additional shot); you've got enough shots in the group to characterize that gun/ammo combo--no need to shoot any more.

You can set up an excel spreadsheet, or something similar, to do the calculation so you don't have to manually perform the calculation over and over again. You just poke in the horizontal and vertical coordinates for each shot and recalculate the mean and variance for each coordinate set.

You get to decide the exact definition of "stabilize"--how much change is significant--since it's your test, but this should be the quickest way to determine how large a group size you need to adequately characterize a gun/ammo combination.
 
Thank you, lordpaxman.

For pistol testing, I am not aware of barrel temperature criteria and I don't plan on using such.

For 16" 9mm carbine testing, I live at the coast and most of my 10 round group testing is done with cold barrel as average ambient temperature runs around 50Fs to 60Fs when I usually conduct my range testing and barrel cools down between groups. That said, as I approach 50 round group testing, barrel temperature increase may be a factor I will watch out for.

For barrel cleaning, it will be with Hoppe's #9 solvent and Viva paper towel patches.

JohnKSa said:
Grid off your target and record the impact point for each shot as a two number position with one number being the horizontal position and the other the vertical position, both relative to the impact point.

After each shot, calculate the mean and variance for both the horizontal and vertical data sets. When the means and variances for both the horizontal and vertical data sets stabilize (stop changing significantly with each additional shot); you've got enough shots in the group to characterize that gun/ammo combo--no need to shoot any more.
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I will keep this in mind as if I end up shooting a ragged hole group after 20 rounds, there's no point in shooting into the hole if 30-40 rounds won't increase the ragged edge size.
 
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...if I end up shooting a ragged hole group after 20 rounds, there's no point in shooting into the hole...
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That's the simplest version of what I'm describing. But the method I described will let you know, after any number of rounds have been shot, and regardless of the overall size of the group, if additional shots won't really change the statistics of the group. Once the mean and variance stabilize--stop changing significantly--you've shot enough shots into that group and shooting more won't really provide any more information.

Of course, on the other hand, it might tell you, in some cases, that 50 rounds isn't enough--that the statistics of the group still aren't nailed down and you need to shoot more.
 
JohnKSa said:
That's the simplest version of what I'm describing. But the method I described will let you know, after any number of rounds have been shot, and regardless of the overall size of the group, if additional shots won't really change the statistics of the group. Once the mean and variance stabilize--stop changing significantly--you've shot enough shots into that group and shooting more won't really provide any more information.
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Yes, I agree. And if such is the case, as you suggested, I will use a grid target.

Here's a powder work up of 10 round groups of IMR Target at 25 yards. 4.2-4.3 gr load already produced a single hole with 10 rounds. If additional rounds won't increase the hole size, I will definitely use the grid target to see behavior of additional rounds.

index.php


Here's 50 yard 10 shot groups of W231/HP-38 and Promo. I can already anticipate 20 round groups becoming ragged holes and would benefit from grid targets.

index.php
 
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