75 yard groups vs 100 yard groups. from .9moa to 1.5moa. Ammo or me?

[iodine]

Hey gang. Running into something very curious.

Scenario:

Indoor, about 80º F, no wind
MkII FVSR Suppressed, 4.5-27x Athlon Eres BTR Gen 2, Boyd's Varmint Stock
CCI SV 1070fps 40gr
Bipod & Rear Bag

Situation:

I can consistently hit sub-moa groups at up to 80 yards indoor. However, once i get the target to 100y (i haven't tried 81-99 yards)

Below are pics of 75 yards x 10 shots and 100 yards x 5 shots (because more shots wouldn't change anything for proof of concept).

Any Idea what the issue is here? Is it ammo? Are there some recommendations you would make for better choices? Not necessarily looking for one right answer, but more of a discussion on the ballistics (of course recommendations are helpful too!).

It looks like the rounds are opening up widely at 100 yards vs 75 yards.

Thanks in advance!

EDIT: Thanks to all the good info here. I'm now seeing a lot of threads showing my exact scenario. My conclusion is that CCI SV just won't perform to what I think it should at 100 yards. It appears I would need a HV load (or better match load SV) for > 100y, and SV for < 100 y.


75 yards x 10 shots

100y x 5 shots

 

[iodine]

Edit: FVSR in a Boyds varmint stock

 

[Mr. Wolf]

I’ve found that for rimfire rifle shooting, doubling the distance triples the group dispersion. So increasing 25% could increase the grouping by 33%… or in your case roughly from 1 MOA TO 1.5 MOA. Rifles with rotary magazines, non-controlled feed, and drive band damage from feeding compounds the dispersion. Then you add the 40-50 fps ES spread in target grade ammo and 1.5 MOA is a very decent result at 100 yards.

A quick view of jbell’s 6x5 thread here in the rimfire section will show how challenging it can be to group less than MOA at 100 with the 22 lr.

Hope that helps, happy shooting and YMMV

 

[iodine]

I’ve found that for rimfire rifle shooting, doubling the distance triples the group dispersion. So increasing 25% could increase the grouping by 33%… or in your case roughly from 1 MOA TO 1.5 MOA. Rifles with rotary magazines, non-controlled feed, and drive band damage from feeding compounds the dispersion. Then you add the 40-50 fps ES spread in target grade ammo and 1.5 MOA is a very decent result at 100 yards.

A quick view of jbell’s 6x5 thread here in the rimfire section will show how challenging it can be to group less than MOA at 100 with the 22 lr.

Hope that helps, happy shooting and YMMV

This is great insight and thank you for the thread suggestion! I'll definitely check it out.

It's odd because **sometimes** i will get two shots sub-moa (in succession) at 100y, but then the others are way off. It's like... as if something ballistically is happening (which is of course the case), but I just wish i could nail it down. Inconsistent loads, perhaps, as you mentioned.

Definitely not complaining about being able to hit a 4x6" postcard consistently at 100 yards with such a round, just wish i understood why the spread.

The joys of .22!

 

[justin amateur]

CCI SV is not precision target ammunition.
It's bulk 22lr intended for offhand short range hunting and plinking.
Call customer service at CCI and ask them what the expected accuracy is?
Cody informed me that CCI expects to average 2 moa for 5 shots at 100 yards.
Average, got it? Sometimes more, sometimes less.
So one group could be 0.5 inch, the next 3.5 inches.
The average would be 2 inches or 2 moa at 100 yards.

Use a ballistic chronograph and relate results to mv measurements.
Use Mark I eyeball and inspect those cartridges for dents, dings,
damaged drive bands or uneven or sloppy seating.
The visible problems explain those odd strays.

 

[iodine]

CCI SV is not precision target ammunition.
It's bulk 22lr intended for offhand short range hunting and plinking.
Call customer service at CCI and ask them what the expected accuracy is?
Cody informed me that CCI expects to average 2 moa for 5 shots at 100 yards.
Average, got it? Sometimes more, sometimes less.
So one group could be 0.5 inch, the next 3.5 inches.
The average would be 2 inches or 2 moa at 100 yards.

Awesome thoughts. I was previously informed that CCI SV 1070 would be about the best bulk I could get, and it has otherwise been great.

I'll do some research on some match loads.

 

[justin amateur]

The phrase "best bulk" might be an oxymoron.

Does that mean we're discussing degrees of bad?

Comparing CCI to Winchester, Federal or Remington bulk 22lr?

 

[iodine]

The phrase "best bulk" might be an oxymoron.

Does that mean we're discussing degrees of bad?

Comparing CCI to Winchester, Federal or Remington bulk 22lr?

As opposed to the worst bulk? Ha. Good point, however. Any recommendations?

 

[justin amateur]

Actually I do.
Not particularly scientific, but real world examples of large sample results.
For you to compare brands and types of rimfire.
Decide for yourself which fits your requirements.

25 at 100

Yeah, I know, there's an ammo shortage. :rolleyes: How can I waste valuable 22lr on the same old same old. Because I won't have to fire a single shot, it's already been done. All I have to do is some target analysis. It'll take a little bit to get this completed, but not 2-1/2 years like the 50...

www.rimfirecentral.com

https://www.rimfirecentral.com/threads/50-at-100.1204943/

50 at 200

I think I've come up with a useful scenario...maybe. :rolleyes: 50 shots at 200 yards, rimfire, whatever setup makes you happy. 22lr, 17 hmr, 22wmr, 17hm2, 17wsm, all brands, all types. Full benchrest setup, bipod, bags, or one-piece test rest, it doesn't matter. Grab a chunk of cardboard...

www.rimfirecentral.com

 

[iodine]

Actually I do.
Not particularly scientific, but real world examples of large sample results.
For you to compare brands and types of rimfire.
Decide for yourself which fits your requirements.

25 at 100

Yeah, I know, there's an ammo shortage. :rolleyes: How can I waste valuable 22lr on the same old same old. Because I won't have to fire a single shot, it's already been done. All I have to do is some target analysis. It'll take a little bit to get this completed, but not 2-1/2 years like the 50...

www.rimfirecentral.com

https://www.rimfirecentral.com/threads/50-at-100.1204943/

50 at 200

I think I've come up with a useful scenario...maybe. :rolleyes: 50 shots at 200 yards, rimfire, whatever setup makes you happy. 22lr, 17 hmr, 22wmr, 17hm2, 17wsm, all brands, all types. Full benchrest setup, bipod, bags, or one-piece test rest, it doesn't matter. Grab a chunk of cardboard...

www.rimfirecentral.com

Thank you!

 

[DownhillFromHere]

I was previously informed that CCI SV 1070 would be about the best bulk I could get, and it has otherwise been great.

"Bulk" is the operative word. If you're getting 1.5" groups at 100 pretty consistently, that's about as good as it gets with CCI SV. "Best bulk" is akin to "best junk." It's good for close-up run&gun or positional practice out to 100 yards (with large-ish 2" targets), but it's simply not made for anything approaching "precision." Even CCI's "Green Tag" ammo falls far short of "precision."

At the low end of "match" labels would be SK Standard+ or Eley CLub or Contact - price point $6.00-7.00 per box of 50. The oft-recognized "sweet spot" of rimfire is Lapua Center-X at $12-13 per box. Eley Team is at similar price point. At the high end would be Lapua X-Act or Eley Ten-X. There are several Lapua/SK (same company) and Eley labels on the price continuum, and there are other brands/labels like Norma and Federal... but Lapua and Eley are the big names. Unless you're shooting big targets at very close range, just forget about Remington, Winchester, CCI, etc. - as well as anything that comes loose in a jar or can or says "high velocity."

True "match" .22LR ammo is expensive compared to bulk stuff. That's the way it is. I encountered a guy at the range some time ago with a shiny new CZ-457 MTR - nice rifle. He was puzzled because he had been told it was highly accurate, but he was seeing 2-3" groups at 50 yards. Beside the rifle was the garbage labeled "Bucket 'a Bullets." I gave him a box of old Wolf Match Target (relabeled SK Standard+) and he was astounded at much difference it made.*

Best way to learn quickly is spend a lot of time reading here on SH. You'll learn that .22s are sensitive to brand/label/lot of ammo and places to buy bricks or cases of ammo at better prices than the big names like Midway or Brownells. It's a deep, deep rabbit hole. Jump on in.

*Edit: I ran into him again a few weeks later. He had gone out and bought a brick of current-production Wolf Match Target, and was confused as to why it didn't perform as well as what I gave him. Reason: Current-production Wolf Match Target is rebranded Eley of some flavor, and his rifle didn't like the Eley as well as the Lapua - the old stuff was made by Lapua (parent of SK). One of the many twists&turns of the .22 world.

 

[Mr. Wolf]

Deep rabbit hole indeed.
Since it really isn’t yet practical to reload 22lr, the load development like in centerfire cartridges do not apply.
I probably went through 10 different ammo before finding the right match.

The most economical method may be to call Goodshootinginc and ask for Cathy’s sampler pack. Once you find the ammo your rifle likes, buy as much as you can or allowed to buy.
Probably the best time and sanity efficient way is to send it to the Eley or Lapua testing center where they will lot test ammo in their indoor range.

Welcome to the whacky world of rimfire

 

[Emerson0311]

5 shot groups with Rimfire do not represent reasonable expectations. I find 10 at a minimum are required to give a decent idea of what you can expect. Also 50 yds to 100 yds multiply group size by 2.6 or so. That’s what lot tested ammo seems to do in the ammo testing centres.

 

[DownhillFromHere]

The most economical method may be to call Goodshootinginc and ask for Cathy’s sampler pack. Once you find the ammo your rifle likes, buy as much as you can or allowed to buy.

Except Cathy, in the vernacular, ain't got no samples t'sell. Of 33 labels of Eley, Lapua, and RWS on their web site, they're showing less than one brick of Eley Team and less than two cases of SK Pistol Match Special in stock. I asked her months ago about an expected ETA for SK Std+... yeah. That was months ago.

Probably the best time and sanity efficient way is to send it to the Eley or Lapua testing center where they will lot test ammo in their indoor range.

Agreed... Don't know about Killough's (Eley testing), but someone said Lapua's wait list is out a couple of months and purchase amount is limited (I haven't verified this). Killough's looks to have stock of several Eley labels.

 

[MarkCZ]

It could be a few things going on. Are you shooting at public indoor range? They have fans that circulate the air, you could be hitting moving air around 100yds. What is your shooting setup, is it steady.

Ammo is next. How does it shoot at 50yds? Have you tried other ammo? If not try some other ammo. I shoot SK line and Eley Club, works well for me.

Has the gun been cleaned lately?

 

[MajorD]

While I wouldn’t quite call CCI standard velocity bulk junk, and I don’t have the technically elegant responses some have offered, bottom line yes it is the ammo and stepping up to SK. eley or lapua is the answer.
my mark 2 did well with eley club just a little more expensive than CCI
when looking for best accuracy ( there is an exceedingly rare fluke every now and then) you have to forget anything American made and use European ammo

 

[10ring1]

Rimfire is its own beast. If one shoots 1/2" groups at 50y don't expect 1" or less at 100y. Groups open much faster than CF

 

[iodine]

It could be a few things going on. Are you shooting at public indoor range? They have fans that circulate the air, you could be hitting moving air around 100yds. What is your shooting setup, is it steady.

Ammo is next. How does it shoot at 50yds? Have you tried other ammo? If not try some other ammo. I shoot SK line and Eley Club, works well for me.

Has the gun been cleaned lately?

"could" be some HVAC down at the end, i could ask.

i have only tried others like federal and other CCI, etc.

gun gets cleaned on a regular, but not overly, basis.

50 yards is essentially one hole after ten rounds. I'll check out SK and others. Thanks!

 

[iodine]

"Bulk" is the operative word. If you're getting 1.5" groups at 100 pretty consistently, that's about as good as it gets with CCI SV. "Best bulk" is akin to "best junk." It's good for close-up run&gun or positional practice out to 100 yards (with large-ish 2" targets), but it's simply not made for anything approaching "precision." Even CCI's "Green Tag" ammo falls far short of "precision."

At the low end of "match" labels would be SK Standard+ or Eley CLub or Contact - price point $6.00-7.00 per box of 50. The oft-recognized "sweet spot" of rimfire is Lapua Center-X at $12-13 per box. Eley Team is at similar price point. At the high end would be Lapua X-Act or Eley Ten-X. There are several Lapua/SK (same company) and Eley labels on the price continuum, and there are other brands/labels like Norma and Federal... but Lapua and Eley are the big names. Unless you're shooting big targets at very close range, just forget about Remington, Winchester, CCI, etc. - as well as anything that comes loose in a jar or can or says "high velocity."

True "match" .22LR ammo is expensive compared to bulk stuff. That's the way it is. I encountered a guy at the range some time ago with a shiny new CZ-457 MTR - nice rifle. He was puzzled because he had been told it was highly accurate, but he was seeing 2-3" groups at 50 yards. Beside the rifle was the garbage labeled "Bucket 'a Bullets." I gave him a box of old Wolf Match Target (relabeled SK Standard+) and he was astounded at much difference it made.*

Best way to learn quickly is spend a lot of time reading here on SH. You'll learn that .22s are sensitive to brand/label/lot of ammo and places to buy bricks or cases of ammo at better prices than the big names like Midway or Brownells. It's a deep, deep rabbit hole. Jump on in.

*Edit: I ran into him again a few weeks later. He had gone out and bought a brick of current-production Wolf Match Target, and was confused as to why it didn't perform as well as what I gave him. Reason: Current-production Wolf Match Target is rebranded Eley of some flavor, and his rifle didn't like the Eley as well as the Lapua - the old stuff was made by Lapua (parent of SK). One of the many twists&turns of the .22 world.

Overall great insight. Thank you!

 

[RTH1800]

5 shot groups are perfect for showing what your rifle will do for 5 shots. They get bad mouthed here a lot. That the more you shoot the larger the group will be is obvious. But not all group enlargement is due to the rifle or ammo. It can be wind, light, ammo in the sun etc. Shooter eye fatigue or simply lack of concentration also figures into it. Five 5 shot groups tells me all I need to know about my set up.

Once I do that, I check cold bore POI a few times and shoot a group once or twice a year or if I start missing squirrels. Record Temp/impact data as often as I get it.

But, I am just a small game hunter who has a few very accurate rifles.

 

[iodine]

5 shot groups are perfect for showing what your rifle will do for 5 shots. They get bad mouthed here a lot. That the more you shoot the larger the group will be is obvious. But not all group enlargement is due to the rifle or ammo. It can be wind, light, ammo in the sun etc. Shooter eye fatigue or simply lack of concentration also figures into it. Five 5 shot groups tells me all I need to know about my set up.

Once I do that, I check cold bore POI a few times and shoot a group once or twice a year or if I start missing squirrels. Record Temp/impact data as often as I get it.

But, I am just a small game hunter who has a few very accurate rifles.

Couldn’t agree more. Five shots is enough for me to know if something is going wrong - and what to diagnose, or if things are going well - and what to keep doing.

 

[MarkCZ]

5 shot groups are perfect for showing what your rifle will do for 5 shots. They get bad mouthed here a lot. That the more you shoot the larger the group will be is obvious. But not all group enlargement is due to the rifle or ammo. It can be wind, light, ammo in the sun etc. Shooter eye fatigue or simply lack of concentration also figures into it. Five 5 shot groups tells me all I need to know about my set up.

Once I do that, I check cold bore POI a few times and shoot a group once or twice a year or if I start missing squirrels. Record Temp/impact data as often as I get it.

But, I am just a small game hunter who has a few very accurate rifles.

I don't know where the 10 shot groups come from, must less the 20, 25 and 50 rounds groups. I come from a lot of centerfire, where it is 5 shot groups are the norm. I would not know what is going on while I am firing it. As you said, Between wind, light, heat of the gun, gun handling, etc.
I am with you. Five 5 shot groups will tell you everything you need to know about the gun and ammo. you can get a 5 shot group off under the same conditions most of the time.

 

[DownhillFromHere]

I don't know where the 10 shot groups come from, must less the 20, 25 and 50 rounds groups. I come from a lot of centerfire, where it is 5 shot groups are the norm. I would not know what is going on while I am firing it. As you said, Between wind, light, heat of the gun, gun handling, etc.
I am with you. Five 5 shot groups will tell you everything you need to know about the gun and ammo. you can get a 5 shot group off under the same conditions most of the time.

It is entirely correct to say that five 5-shot groups will tell you a lot and marksmanship is paramount, but I submit that, in competition, it's important to know how a given lot of ammo performs over 50, 100, or even more rounds to really know what to expect at extended range.

Here is a 100-yard mini-Palma target set from a match earlier this month. Total of 45 shots scored, perfect score is 450/45x. I lucked out and had no weak rounds in a little over 50 rounds of lot-tested* Lapua Center-X fired (including sighters). But I lost a match earlier this year when I had a weak round on a 100-yard steel target - no wind, rock solid gun mount on bipod/rear bag/bench, good trigger pull, huge target (I cleaned the rest of the match including much smaller targets).

Would Midas+ or X-Act do better in consistency (I shoot a Vudoo, chambered for Lapua)? Maybe. But Center-X currently sells at Good Shooting, if they can get it, for 26 cents a round (rounded up to nearest cent). Midas+ is 33 cents a shot, X-Act 52 cents. Eliminating a slightly weak round or two out of hundreds isn't worth the price premium to me, and the target below shows that, in my rifle, Center-X is "good enough." Most of the matches I shoot (out to 450 yards) require more marksmanship abilities than benchrest accuracy, but I like having the knowledge of what my ammo will do.


* Lot tested at the Lapua Rimfire Performance Center in AZ. It's worth every dime (and the cost of testing is dirt cheap considering the ammo expended) to have your rifle tested out to 100 meters (109 yards) with multiple lots of great to excellent ammo and then be able to lay in a case of it (before shortages, multiple cases if you wanted).

 

[Mr. Wolf]

"could" be some HVAC down at the end, i could ask.

i have only tried others like federal and other CCI, etc.

gun gets cleaned on a regular, but not overly, basis.

50 yards is essentially one hole after ten rounds. I'll check out SK and others. Thanks

When I had Lapua lot tested, they did ten shots initially to see if it would group well. If that lot grouped well enough, they would shoot 10 more to verify. In my experience, Luke saw 3 lots that looked promising and selected the one that had the most circular dispersion, not necessarily the smallest group (of the 3 lots that he picked). My guess is that it probably has to do with statistical significance as they used a different measure than overall group size. Check out this article: https://www.snipershide.com/precisi...est-facility-what-should-you-expect-in-gains/

My CZ 457 pro varmint stock 16" barrel shot about the same as the Lothar-Walther aftermarket 20.5" barrel at 50 yards.
Where I notice the difference is in shots >100 yards. Approx 50% of the 5 shot group were under 1" with the stock barrel, but the first time out with the Lothar Walther aftermarket barrel, 6 of 6 5-shot groups were under 1". Lastly, the longer barrel is more forgiving with different ammo. Center X has the tightest groups, but SK rifle match and the SK standard + are only .1" bigger at 50 yards.

YMMV, happy shooting

 

[Williwaw]

It is entirely correct to say that five 5-shot groups will tell you a lot

With respect I submit that five 5-shot groups, ie five max spread measurements, provides an absolutely minimally statistically significant representation of the rifles performance. It may be all the prior posters feel they are looking for but it is only correct to say that five 5 shot groups tell you almost nothing unless your expectations and standards are minimal.

 

[Emerson0311]

With respect I submit that five 5-shot groups, ie five max spread measurements, provides an absolutely minimally statistically significant representation of the rifles performance. It may be all the prior posters feel they are looking for but it is only correct to say that five 5 shot groups tell you almost nothing unless your expectations and standards are minimal.

22 ammo is so inconsistent that 5 rnd groups show very little. You are kidding yourself if you make decisions based on 5 shot groups of 22LR.

 

[Williwaw]

5 shot groups are perfect for showing what your rifle will do for 5 shots.

No truer statement could be made.

They get bad mouthed here a lot.

I wouldn't say bad mouthed, I would say correctly represented as being nearly the least useful metric available for serious rimfire shooters.

That the more you shoot the larger the group will be is obvious. But not all group enlargement is due to the rifle or ammo. It can be wind, light, ammo in the sun etc. Shooter eye fatigue or simply lack of concentration also figures into it. Five 5 shot groups tells me all I need to know about my set up.

Lets not leave out group enlargement due to the fact that multiple five shot groups do not share a common midpoint and therefore give only an optimistic estimate of rifle precision and a questionable indication of POI.

I'm aware that you are quite confident and satisfied with your choices. I'm simply home, sick, bored, and feeling inclined to provide an alternate view.

 

[grauhanen]

Without getting into the issue of how many shots in a group are needed to evaluate ammo or whether five shot groups have merit in that regard, there was an interesting discussion a few months ago on RFC -- marred by no small amount of chaff -- about using two shot groups when comparing different lots of ammo. See especially the posts by the OP "elsdude" and post #19 by jbrossman1938 (formerly MKnarr on RFC) https://www.rimfirecentral.com/threads/two-shot-group-shooting-i-think-its-time-has-come.1248654/

See also the attachment which has many more details, including the "math" behind the approach.

 

[Old Man with Gun]

I think 22lr shines at 50yds.
Groups at 75 are double 50 and 100 are double 75.
If you want tiny rimfire groups at 100yds consider 17HMR.

 

[JustSendit]

With respect I submit that five 5-shot groups, ie five max spread measurements, provides an absolutely minimally statistically significant representation of the rifles performance. It may be all the prior posters feel they are looking for but it is only correct to say that five 5 shot groups tell you almost nothing unless your expectations and standards are minimal.

If you shot a 5x5 and it grouped terribly in all 5 groups. Would continue to test that load/bullet? Or could you determine, some conclusions?

 

[justin amateur]

17 hmr? Maybe. Depends on y'er luck with the assembly line lottery.
I've had 17 hmr cartridges that showed 3 moa at 100 yards.
Neither CCI or Winchester make precision paper punching ammo.
The 17 hmr, 22 wmr, 17 wsm and 17 hm2 are varminting and hunting ammo.
Offhand, center of critter and meat spray, they do the job.
Benchrest USBR Green monster, they sling too many strays
due to inconsistent components and assembly.

5 shot groups are for adjusting y'er scope to current conditions and ammunition.
One dot-one shot targets are for proving y'er ability to meet the requirements of Rule #1 - Hit what you aim at.
When testing ammunition quality, small sample sizes will cause you to draw incorrect conclusions.
That's what happens at the factory when batch testing for lot grading.
Testing for quality is time consuming and expensive, so they use statistical sampling.
Small portions of each run are sent through fixtured barrels in a test tunnel.
Those that produce the best results are sold at a higher price.
Is that going to guarantee our results will be as good? No.
Small sample sizes can cause incorrect conclusions, remember?
If you have a run of 12,000 cartridges and you test using standard statistical methodology,
an 90% confidence level (9 times out of 10 you get the same results)
according to a sample size calculator it's only necessary to test 265 cartridges.

If you buy 500 cartridges, 90% confidence level, you need to test 176.
5000 cartridges, 90% CL, 257 need to be tested. See the problem?

That's why so many folks end up unhappy with the results from supposedly the best ammo.
Statistical sampling is not a guarantee of obtaining the same results.
It simply allows the manufacturers to state the ammunition has been tested for quality, and charge more.
Those small sample sizes only state the results obtained with the samples, not the entire batch.

Try punching in the numbers for y'erself.

Sample Size Calculator - Qualtrics

Need to quickly calculate sample size? Use our calculator to find your ideal sample size now! ✓ Learn more with this complete guide.

www.qualtrics.com

So you buy 2 cases from the factory test center.
10,000 cartridges, how many shots need to be tested
to obtain a 99% confidence level you've bought the right lot number?
How about 399, not 5, or 10, or 25, or 40. According to statistical sampling, 399.
Anything less and y'er still just playing the assembly line lottery.


RT, this last bit is just for you.

When testing ammunition quality:

5 shots is a random act of accuracy.
10 shots is a wallet group.
25 shots is a good start.
50 shots is the bare minimum needed when testing y'er last delivery.
100 shots and I can be pretty sure of the quality of the cartridges I just purchased.

 

[Williwaw]

If you shot a 5x5 and it grouped terribly in all 5 groups. Would continue to test that load/bullet? Or could you determine, some conclusions?

Morning Sendit,

I would likely set that ammo aside for testing tomorrow. Being rimfire and having such a small sample means I can't confidently conclude anything at this point but I find it tough to carry on in the face of real dismal results. So I would not continue to test and I would draw no conclusions.

 

[cas6969]

Have you shot them any farther to see if there's any signs of destabilizing?


Made me think of a pistol/bullet combination I played with years ago. At 25 yards it shot real nice tight groups. At 50 they knuckle balled to 18-24" groups.

 

[Williwaw]

Justin,

I think there may be a flaw in applying the numbers supplied by the link to rimfire precision. The authors are dealing with interview results of survey questions, not physical measurements.

So if the question was how many won't fire you might be good. But if the question is will the average round hold within .125 inches of center then much larger samples are required.

Don't know ... been wrong before.

 

[justin amateur]

Willi, it's a sample size calculator.
I've tried a half dozen of them.
Some dealing with opinion surveys, some with quality control.
All have some additional input that can be changed,
but the basic sample size numbers work out almost the same.
Quality control includes acceptable defect rates and failure percentages per thousand
but the sample numbers needed for testing are affected minimally.
I'd like someone with a true background in quality control
to offer an experienced explanation of what is needed in the batch grading process.

AQL CALCULATOR | ACCEPTABLE QUALITY LIMIT

AQL Calculator & Acceptable Quality Limit are statistical tools, widely used in the QC industry to determine the sample size for inspection.

tetrainspection.com

 

[RTH1800]

We seem to have the same discussions over and over.

I really respect Justin’s input and post. Wish he lived closer so we could compare results and observations in person.

I think the disconnect is based on our goals.

I am a small game hunter. Squirrels, crows, rabbits and elephants primarily.

After testing literally dozens of rifles I am satisfied I have some of the best .22’s ever made. I have no physical or visual impairments that limit my ability to get the most out of my equipment and ammo.

I read about point of impact shifting. Other than condition induced shift, mine do not move. They are bedded by a great stocker.

My rifles do not shift POI due to position. My triggers are well adjusted and consistent but 2-4# pulls. They do not vary.

My interest is in hit probability on a given shot. Do I shoot, move closer, get a better rest?

My data book has settings to 200 yards in 10 yard increments. Temperature graphs from 20-90 deg F.

I know that I can go to the range this afternoon and in calm, evening conditions shoot one shot at 25,50, 75, and 100 yards, 1/4”, 3/8, 3/4 and 1” dots. My best rifle will place the bullet touching the dot at each range. At 200 yards a 2” dot will be hit 3 out of 5 shots with the others well within 3”.

I really do not care that a statistician determined that one shot in 399 will miss this goal. Within my and my equipment’s know ability, I’m taking the shot.

Most trips result in no misses and a limit of squirrels shot in the eye at ranges from 25 to 125 yards.

My results are in line with my goals.

 

[acudaowner]

well it could be the gun or the gun not liking the ammo but I really do not buy into my gun liking or disliking anything as it's only a tool and has no real feelings either way . it could be you and all or any of the above or it could have been a butterfly somewhere on the planet fucking with you and passing wind either way keep at it your groups are sure to tighten up till your eyes and you get older and older till you can't see squat lol . you could try strapping your gun to a table taking the you part out of it all just for comparison then you would know how much is you and what is or isn't your gun or ammo .

 

[justin amateur]

RT, our goals are identical.
Rule #1....hit what you aim at.

The difference between us is I like discussing ammunition quality.
Possibly too much.

Woods time is about finding out how close I can get before the critter can react.
Range time is about figuring out why the ammunition behaves as it does.
Was it wind? Me? Setup or ammunition?

Does it make the ammunition better than it is? No.
Does it make the ammunition worse than it is? No again.

Does it give me something to think about during those slow times at the office?
Oh yeah.

 

[RTH1800]

I think a question raised earlier was interesting.
If a great 5 shot group tells you nothing what does a crap 5 shot tell you?

 

[RTH1800]

RT, our goals are identical.
Rule #1....hit what you aim at.

The difference between us is I like discussing ammunition quality.
Possibly too much.

Woods time is about finding out how close I can get before the critter can react.
Range time is about figuring out why the ammunition behaves as it does.
Was it wind? Me? Setup or ammunition?

Does it make the ammunition better than it is? No.
Does it make the ammunition worse than it is? No again.

Does it give me something to think about during those slow times at the office?
Oh yeah.

The joy of picking a couple of grey squirrels out of a burr oak at 105 yards with two clean headshots cannot be overstated.

I once shot 5 in about 20 seconds at 78 yards emerging from a den tree hole. As fast as I worked the bolt another popped it’s head out. They were all in a small pile touching. (Great group)

 

[RTH1800]

@justin amateur

Your best message, which I think is still not fully appreciated, is that no rifle “likes” crap ammo. It cannot be “fixed”. It’s just crap.

Conversely, no ammo can “fix” a poor rifle.

Not sure why that is difficult to understand for some folks. But I know you will keep trying to explain it!

 

[MarkCZ]

17 hmr? Maybe. Depends on y'er luck with the assembly line lottery.
I've had 17 hmr cartridges that showed 3 moa at 100 yards.
Neither CCI or Winchester make precision paper punching ammo.
The 17 hmr, 22 wmr, 17 wsm and 17 hm2 are varminting and hunting ammo.
Offhand, center of critter and meat spray, they do the job.
Benchrest USBR Green monster, they sling too many strays
due to inconsistent components and assembly.

5 shot groups are for adjusting y'er scope to current conditions and ammunition.
One dot-one shot targets are for proving y'er ability to meet the requirements of Rule #1 - Hit what you aim at.
When testing ammunition quality, small sample sizes will cause you to draw incorrect conclusions.
That's what happens at the factory when batch testing for lot grading.
Testing for quality is time consuming and expensive, so they use statistical sampling.
Small portions of each run are sent through fixtured barrels in a test tunnel.
Those that produce the best results are sold at a higher price.
Is that going to guarantee our results will be as good? No.
Small sample sizes can cause incorrect conclusions, remember?
If you have a run of 12,000 cartridges and you test using standard statistical methodology,
an 90% confidence level (9 times out of 10 you get the same results)
according to a sample size calculator it's only necessary to test 265 cartridges.

If you buy 500 cartridges, 90% confidence level, you need to test 176.
5000 cartridges, 90% CL, 257 need to be tested. See the problem?

That's why so many folks end up unhappy with the results from supposedly the best ammo.
Statistical sampling is not a guarantee of obtaining the same results.
It simply allows the manufacturers to state the ammunition has been tested for quality, and charge more.
Those small sample sizes only state the results obtained with the samples, not the entire batch.

Try punching in the numbers for y'erself.

Sample Size Calculator - Qualtrics

Need to quickly calculate sample size? Use our calculator to find your ideal sample size now! ✓ Learn more with this complete guide.

www.qualtrics.com

So you buy 2 cases from the factory test center.
10,000 cartridges, how many shots need to be tested
to obtain a 99% confidence level you've bought the right lot number?
How about 399, not 5, or 10, or 25, or 40. According to statistical sampling, 399.
Anything less and y'er still just playing the assembly line lottery.


RT, this last bit is just for you.

When testing ammunition quality:

5 shots is a random act of accuracy.
10 shots is a wallet group.
25 shots is a good start.
50 shots is the bare minimum needed when testing y'er last delivery.
100 shots and I can be pretty sure of the quality of the cartridges I just purchased.

Are you saying 100 rounds in one group will tell you everything you need to know. but 20 5 shot group will not tell you anything.

 

[justin amateur]

Nope.
20 five shot groups will tell you the same thing as the 100 shot group.
Build the total aggregate group size relative to the aimpoints. Don't average group sizes.
A single 5 shot group is too small a sample when verifying ammunition quality. That's the random act accuracy.
A ten shot group is still not a large enough sample.
Y'er checking ammunition quality so a large sample size is needed.
Try that sample size calculator and see how many are needed for a 99% confidence level.

 

[RTH1800]

The first crow said “145 yards, his sample 5 shot group was a random act of accuracy” Splat!

The second crow said “

155 yards, bet you can’t do that again” Splat!

 

[grauhanen]

Y'er checking ammunition quality so a large sample size is needed.
Try that sample size calculator and see how many are needed for a 99% confidence level.

Indeed. Justin has it right. The is the bottom line is always about the sample size. What's important is how much data is available, whether it's collected in five-shot or ten-shot groups.

 

[MarkCZ]

Nope.
20 five shot groups will tell you the same thing as the 100 shot group.
Build the total aggregate group size relative to the aimpoints. Don't average group sizes.
A single 5 shot group is too small a sample when verifying ammunition quality. That's the random act accuracy.
A ten shot group is still not a large enough sample.
Y'er checking ammunition quality so a large sample size is needed.
Try that sample size calculator and see how many are needed for a 99% confidence level.

100 shot group, how long would it take to fire? During that time, how many wind changes, light changes, temp changes, shooter errors, will take place? How much will that effect the group size and group relative to the aimpoint? How can a 100 rd. group tell you anything? You don't know what has effected the group.

 

[justin amateur]

Good question Mark.
How long does it take to fire 20 five shot groups?
Wind is going to push them around also.
That's why you record conditions and muzzle velocities.
Y'er testing ammunition quality.
Doing the best you can with the equipment, conditions and location you have.
Not all of us have access to indoor test facilities.
Which ammunition produces the best results overall?

I learned that overall aggregate group size offers the most reliable answer.
Not average group size, not best group.
You don't test ammo on a gusty day.
A steady light breeze can be adapted to,
but gusts and turbulence will mess with ya'.

 

[MarkCZ]

A 5 shot group should take 30 sec. 60 sec. if you are taking your time. That group is over, conditions do not effect it any longer. then on to the next. IMO a 100rd. group will show how the ammo shoots, over 20 min. and how the conditions effected it. Not a true test of the ammo. 20 5 shot groups breaks it without all the condition changes.

 

[grauhanen]

When testing ammo, it's essential that outside influences don't influence results. When there's wind, if it isn't accounted for by effective use of wind flags, there's little point in testing.

 

[justin amateur]

Yep, best to test under optimum conditions.
Indoors, from a fixture so skill isn't necessary.
That still doesn't mean you can get away with small numbers of shots.
Need a hefty number of shots to avoid the problem of incorrect conclusions.
Components and assembly tolerances vary over time.
The sample tested needs to cover the entire time of manufacture of the batch,
beginning, middle and end. Otherwise a problem can be missed.
One box of 50 isn't enough.