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Old December 21, 2012, 09:12 PM   #1
Bart B.
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How many shots per group for best accuracy assesment?

Here's a plot of 250 shots fired from a rifle at a 200 yard target.



The numbers 0.5, 1 and 1.5 represent radius from group center in inches; 1/2 inch per circle. Extreme spread's about 2.45 inches.

Reverse shoot this composite group by doing the following:

1. Print this picture on a sheet of paper so the target's about true to scale.

2. For the first 5 shot group, lay the printed target sheet centered on a blank sheet of paper of the same size. Then punch a pin through any five shot circles of your choice. Label that sheet group 1.

3. For the second 5 shot group, repeat the above using five other shot circles without pin holes in them. Label that sheet group 2.

4. For the next fourty-eight 5-shot groups do the same thing labeling each one group 3 through 50. And, if you must "shoot" one really tiny group, pick any group of five circles clustered very, very close together (anywhere) for one of them labling it with another word spelled "s m a l l e s t." There's a good, tiny 5-shot cluster to use at 11 o'clock out about 0.35 inch out from center; another's at 7 o'clock out about 0.4 inch.

5. Pick any two 5-shot sheets, measure the distance between the two widest shot circles then write on that sheet.

6. Lay each 5-shot sheet on another sheet then pin punch each one so all 10 punch marks are on that sheet. That's a 10-shot group composite. Measure its extreme spread and label it as group 1 and 2 ten shot composite

7. Repeat steps 3, 4, 5 and 6 with the next four, then six, then twelve, and finally the last twenty-six 5-shot sheets labeling them accordingly.

Now look at all those 5-shot groups and many shot composites. Each 5-shot group represents what 2% of all the fired groups is. The last twenty-six 5-shot group composite of 130 shots represents what the accuracy is about 90% of the time.

How many shots per group does it take for the group to best represent the accuracy of the rifle, ammo and shooter for you?
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Old December 21, 2012, 10:51 PM   #2
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Old December 21, 2012, 11:32 PM   #3
Art Eatman
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When I get a new-to-me rifle, I test it with a five-shot group; maybe a couple of groups. Then I go to load development. That usually means several three-shot groups, one group per load.

Whatever works out best gets a five-shot group, maybe a couple. If I'm happy with that, I just do three-shot groups as a back-check before going hunting.

That's worked out nicely for a dozen or so rifles through the years, with multitudes of sub-MOA groups and many a dead deer, coyote or jackrabbit.
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Old December 22, 2012, 12:15 AM   #4
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Ouch! You are heavy into statistics here - binomial distributions, circular error of probability etc and we know what Disraeli (or was it Twain) said

Quote:
"There are three kinds of lies: lies, damned lies, and statistics."
Personally I rather like one-shot groups
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Old December 22, 2012, 12:57 AM   #5
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At 200 yards I'd be happy with any/all of those shots and call them "good enough".

But that's just me. YMMV
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Old December 22, 2012, 09:22 AM   #6
Bart B.
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David, I'm not heavy into statistics here - binomial distributions, circular error of probability etc and I know that what Disraeli (or was it Twain) said about those three kinds of lies: lies, damned lies, and statistics. Whomever said that was (I think) very heavy into ignorance and obviously had poor qualities of observation.

On the other hand, if that group's reference circles were 2, 4 and 6 inches in diameter, that group would near 100% be the same as Lake City Army Ammo Plant's best lots of 7.62 NATO M118 National Match lots made in the 1960's and tested at 600 yards. I've seen a couple of their 200+ shot 600-yard test groups and they have bullet hole distribution exactly the same. The best lots had a mean radius of 1.82" and about 5.5" extreme spread. The average 5-shot group would be about 3.7" extreme spread.
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Old December 22, 2012, 09:39 AM   #7
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Mr. Bobbitt, when I grow up, I want to be just like you!!!

Seriously.
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Old December 22, 2012, 09:52 AM   #8
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Jeeze, Metal God do you have any more aspirin?
When I'm load developing I like to use at least four rounds of each powder weight, and when I strike on something good I prove it with at least three 5 round groups, at this point I'm pretty happy and there's no need to keep wasting powder, unless I'm practicing.
I think that I need at least five round groups when proving repeatability of my loads,, I think they will best represent my findings.
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Old December 22, 2012, 09:53 AM   #9
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Bart- Are these all fired in one day at one setting?. How big is the outside circle?.And what caliber is this?. I only fire 5 per group sometimes 10. Seems if you shoot more than that all you end up with is a big old hole in the paper and you really can't tell where some of the rounds went. I have certain targets i use for testing a load at first and when i am sure i have something to work with. I use those red 1 inch self sticking targets and place a pencil diameter dot in the middle. I use a chunk of coardboard 3 feet wide and place about 30 of those stickers going across it. Then i shoot one round into each target. This gives me a better picture of where i am actually hitting with each shot. Some say i need to do groups,but when i can sink one round into that small dot in the middle on all targets,groups mean nothing as i am hitting right where i want to hit any how. I have a pic of one of my older ones but just don't know how to upload it. Not to computer savey here.
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Old December 22, 2012, 11:45 AM   #10
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I have a couple of Bud’s how shot with Larry Moore on his long range team. Larry Moore was a Government Ordnance Employee who personally tested every potential M1 Garand replacement at Aberdeen Proving Grounds and wrote the test reports. He was also a National Champ at Camp Perry. Here is an article that Mr. Moore wrote in the Dec 1956 Guns Magazine.

http://www.gunsmagazine.com/1956issues/G1256.pdf

One of my Bud’s, a Long Range Champion in his own right, asked Mr Moore just how many rounds it took to have a good idea of the accuracy of a load.

Mr. Moore said “about 20,000”.

Mr. Moore would have known about the hundreds of thousands of rounds fired at LC city developing the yearly National Match ammunition, and 20,000 is probably ball park.

Just this week at the Gun Club December meeting we were laughing about Gunwriters who publish three shot groups as proof about their reloading techniques. Three shots does not prove any trend.
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Old December 22, 2012, 12:07 PM   #11
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Slamefire- Great reading for sure. My only concern is. This was back in 1956. Heck that was before i was born. Guns,Ammo,Brass,Barrels,ect ect have come so far since then that there is no comparision between then and now.
I do agree 3 shot groups is worthless,but 20,000 is just as insane. I guess we need to decide between what rifles we are shooting also. One can not take a run of the mill hunting rifle and expect bench rest rifle accuracy out of it( although you can get darn close). I picked up a 243 about 1 month ago. It was already starting to get to the cold and windy side of things for me to do any load development. I did slam together 5 loads 5 rounds of each from reloaders nest .com. As luck had it one load performed very well for me using IMR4064. I came home loaded another 50 rounds of that load.Got back out to range next week after and again at 200 yards i was inside 1 inch circle with all shots,Now i know 200 yards is not a great distance to shoot and this load could fall apart at 500 and 600 yards,but my point is you do not need to shoot till your barrel is shot to find the right load or to test if your load is going to work. I picked a 6MMBR this spring so i could join F-Class open. Talked with anothe rperson that had same rifle as mine and went with his load.
As it turned out i had to tweak his load in COL and .3 gn's of powder. That rifle will hold 3.5 to 4 inchgroups at 600 yards on any given day. I know it would do much better,but that is up to me.
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Old December 22, 2012, 01:25 PM   #12
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Slamfire's comment:
Quote:
Mr. Moore would have known about the hundreds of thousands of rounds fired at LC city developing the yearly National Match ammunition, and 20,000 is probably ball park.
I doubt LC fired hundreds of thousands of rounds developing any National Match load; either M852 or M118 for 7.62 NATO or M72 for 30 caliber stuff. Prior to about 1970, they typically set aside excellent lots of the 172-gr. match bullets for just such lots of ammo. Each lot of bullets was tested with a known good set of other components kept in reserve for just that. So the bullet was not what tests were done for. Powder lots was the big issue. Primers and cases didn't have much variables. Note that their accuracy test barrels had about a 3000 round life of accuracy suitable for qualifying ammo lots as well as components.

It took only one 300-shot test group to prove a given load's accuracy and velocity specs were met as well as only 20 to 30 more to prove pressure specs were met. When I talked with LC a couple of times in the late 1960's, the man said they usually shot 50 test rounds with a given load to verify it was worth further testing. They changed powder charge weights by 3/10ths grain as I remember but seldom tested primers as they were pretty much consistant across several lots. Therefore, I don't think they shot more than 2,000 rounds max developing any National Match load. Each NM lot consisted of 200,000 to 250,000 rounds or thereabouts; plenty for 1300 competitors to each shoot 150 rounds in all the DCM/CMP matches at the Nationals
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Old December 22, 2012, 01:32 PM   #13
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I have been trying to read everything Bart posts about rifle accuracy since May 1997* and have researched his prior posts.

Bart makes fun of guys that shot a good 5 shot group, cut it out, and carry it in their wallet. He calls that a "wallet group".

Bart, I treasure my wallet groups. I put them on the wall. I brag about them. I aspire to get more wallet groups. It is like remembering that time you went to Vagas and came home with MORE money.




This is a $60 Rem 510 with a $20 scope shooting Win Power Point 22LR ammo. Can you find the wallet group in the picture?









*Leafing through my copy of the May 1997 issue of Precision Shooting, I
encountered an ad for Krieger Barrels, Inc. that showed an actual-size
copy of a 20-shot group shot at 800 yards by "Bert Bobbit [sic] with
his Krieger Barrelled PALMA rifle." Now this group has a .942" mean
radius, with an extreme spread of 3.325. If it were a 5-shot group,
you'd say, "Somebody else has shot that well at 1,000 yards."
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Old December 22, 2012, 04:26 PM   #14
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Quote:
This is a $60 Rem 510 with a $20 scope shooting Win Power Point 22LR ammo. Can you find the wallet group in the picture?
Sure there is . you just don't have a big enough wallet . Maybe you need a purse I shoot purse groups all the time
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Old December 22, 2012, 04:52 PM   #15
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If I had to shoot 250 round groups, I'd never shoot a group.

I've never failed to have 5 or even 3 shot groups tell me everything I need to know about my gun and load.

Do I shoot competition? No. Never have, never will.

But I do shoot animals, pretty small ones, from pretty far away, relatively. My gun can hit them farther away than I can. That's all I really need to know.
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Old December 22, 2012, 05:52 PM   #16
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How many shots? Well, the danger in shooting more shots is that your group opens up, and you measure the group you shot. So in your case, that makes a 1.2 MOA group.

I generally consider 5 shots sufficient, but often shoot 10 just for grins and giggles. They never get better by shooting more shots.

Some guys like to shoot 10 shots then pick the best 3. It doesn't work that way, you measure whatever group you get.

Some guys like to fire 3-shot groups until they get one they like. Fire your groups and take what you get.
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Old December 22, 2012, 06:40 PM   #17
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Quote:
Bart makes fun of guys that shot a good 5 shot group, cut it out, and carry it in their wallet. He calls that a "wallet group".
Well, yeah, but then you are talking about a man, that in the late '90s, shot a group that measured close to 3 inches at 800 yards. IIRC, the mean radius was around 0.8 inches. Now, you might say that many people have shot 3 inch groups at distances much further. But, Bart did it with iron sights (micrometer aperture) and his group was 20 rounds. That is a group to be proud of!

Bart, I hope I am remembering this correctly. You did it with a Palma rifle, did you not?
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Old December 22, 2012, 08:13 PM   #18
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Bartbob Post reply 5/13/97
I used a .308 Win. with Sierra's 155-gr. Palma bullet with 45.3gr. of
IMR4895 and RWS Primers in full-length sized WCC60 match cases. Had a 20X
scope on the English Paramount action and shot prone with a bag under my
front hand to steady the rifle. It was about 6AM in dead-calm wind
conditions.
BB


A 20X scope at 800 yards is like 2.5X at 100 yards.
I have shot enough groups to know I need 10X at 100y to do my best.
I think Bart has really good eyes.
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Old December 23, 2012, 09:12 AM   #19
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I suppose that if a fellow is going to be into competition shooting, working up the perfect load has more meaning. That might lead to the grouping work that BartB has shown. For me, just a hunter and sometime paper puncher, I work up loads that I shoot enough (how much is 'enough') that I believe them to be accurate. I'll load and shoot a particular combination of bullet and powder until I see and believe that it gives me what I need. There's little doubt in my mind that most of my rifles could shoot better if I spent even more time with more powders and more bullets, but even I don't want to work that hard. I find that I spend more time working with the finicky rifles for which I don't yet have that great load combination. Right now I have just one rifle that I'll call finicky. I have a good load for it, but not a great load. Sometimes I wonder if that rifle has a great load. We'll see...I think.

And I don't carry target groups in my wallet, but I do have some of them posted on the wall of my workshop.
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Old December 23, 2012, 10:05 AM   #20
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Thee is no commonly known standard with larger groups. Generally speaking groups are about bragging rights and the standard is moa for 3 or 5 shots.
What is the standard for 25 shots? Sure 1 moa would be awesome but what if its 2 moa, 3 moa? I don't know if that's good or bad. If it were about knowing what the rifle or shooter is capable at a given distance so you are confident you could make xx shot, why not put 25 bullseyes out there and shoot 1 shot at each and see how far off the worst shot is? For every shot in a group you fire you introduce another potential for variability, shooter or environmental. What are you measuring? Shooter capability? Load development? Rifle quality? You can't do any off these successfully without a controls, you can't control wind and temperature, very few if any can control themselves enough to NOT contribute to variability. Bart I have no doubt you are an accomplished shooter, can you confidently say that group is not effected by your ability or environmentals? Load development might be the only truly scientific measurable element of shootings groups, therefore making it the closest thing to a control and we all know there are variables in reloading.
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Old December 23, 2012, 10:22 AM   #21
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1stmar asks me can if I can confidently say that group is not effected by your ability or environmentals?

Well, it sure is.

While my test groups are pretty darned good, they're about 1/3rd the size of what I've shot in competition. I've got a beating heart like my friend has as mentioned in the next paragraph.

A friend tested some specially sorted bullets in his Winchester 70 back in 1971 shooting several 10-shot groups at 600 yards that ranged from 7/10ths inch to 1-1/2 inch. Then he shot 40 shots into a single group measureing 1-15/16ths inch. Shooting the same rifle and ammo at the Nationals that year, his on-target groups in the 600 yard target's scoring rings were about 8 inches. Such is life when human pulse beat pumps muscles around to make even the best prone shooter's hold cover about 4 inches at 600 yards (2/3rds MOA)and those invisible subtle cross winds blow bullets around adding to that. The nasty icing on this accuracy cake is the aperture sights he used; not quite as precise as scopes. But he won all the 600 yard matches that year.

==============================

603country supposes that if a fellow is going to be into competition shooting, working up the perfect load has more meaning.

I've seldom worked up a load for my own use. The loads used in the 800-yard group with my Palma rifle as well as both used in my .30-.338 mag at 1000 yards were what I got from others using the same cartridge in their rifles that won the matches and set the records. The only time I ever worked up a load was back in the 1960's when I tried a .264 Win. Mag. with Norma 139-gr. nickel plated match bullets; no body had used that cartridge in long range matches before. I don't prep cases in any way except sometimes turn necks to get their wall thickness spread no more than 1/1000th. I full length size fired ones. And new cases in my .30 caliber magnums have shot just as accurate as reloaded ones.

With 26 caliber and larger bores, I don't think working up a load has much benefit. Loads used by folks shooting most accurate are pretty much the same for each cartridge. What minute difference there may be is extremely hard to see and will cost a lot of barrel life getting it refined. Seldom does a handloader better what Black Hills or Federal (and sometimes Hornady) match ammo does accuracy wise. Especially if they test it properly (shoot enough shots per test group!!!)
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Old December 23, 2012, 10:47 AM   #22
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I guess anyone can plot what they want and overlap targets why no just look at each target and make the judgment based on that.

Everyone test their load different.
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Old December 23, 2012, 11:01 AM   #23
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Bart that speaks to your ability, which frankly very few have and even at that, 250 shots perfectly placed? Quite a feat, but I will not question your ability. How about the environmentals? Over what period of time did this take? Too quick and the barrel temp is not the same from shot to shot, has that no bearing? Too slow and the ambient temperature changes. Again 250 shots and no risk that there was a gust of wind during the flight time that impacted flight.... My point is not to question your ability but to raise the point that more is not always better as it introduces more opportunity for other influences. That's hard to argue with..
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Old December 23, 2012, 05:24 PM   #24
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When developing a load, I use 5 shot groups until I have the best three. From those 3, I shoot 10 round groups to determine the best. Chrono readings are attached to target. That gives me powder weight for bullet. Process is repeated for powder change. Usually 3 powders. Then best is selected. When bullet is changed, the process is redone.
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Old December 23, 2012, 06:04 PM   #25
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I shoot 5 shot groups. Statistically not valid.

It is fun to me and does not interfere with the rest of my life.

There are so many variables, it is difficult to identify all of them. It is harder to try to isolate them.

Most of us do not shoot our load developments in a vacuum. There are a lot of external variables in play.

Every shot is wearing a little bit of the barrel in addition to heating it up.

I just don't have the drive to try to get that last bit of accuracy. I work at it until I am happy with the results.

I do see some folks out at the range who keep very detailed records of their loads and their groups show it. It is too much like work for me. I do this for fun.
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