This morning I took a second look at the results Joe recently posted in his thread “SOME ACCRACY THOUGHTS” . He was reporting on three different load levels of one powder and was shooting a string of four 5-shots for each load. Joe often reports the size of each individual group in a string as well as the average of that string, an admirable practice IMHO.
I noticed how much the size of his groups varied within each string. I scribbled some numbers and found that the average percentage that the largest group in each four shot string exceeded the smallest group in the string was well over 100%, or the biggest groups were more than twice a big as the smallest groups in the same string.
If the wide variation between groups with the same load was noticed at all, a reader might assume a shaky old guy in Florida caused the variation in group sizes. My groups vary similarly – or course you might say OK, two shaky old guys. Or the reader might assume that the old guys cast very poor quality, are too lazy to weigh sort them, and bullet quality is responsible for the wide variation from group to group as well as the fliers in the groups. (In fact, that is the kind of assumption many of us erroneously make when we notice more variation than we like in where our bullets hit.)
However, if you haven’t noticed similar variations in your own groups, take another look or take a look in the test results in “Dope Bag” section of the American Rifleman. The AR standard testing standard is five 5-shot groups and they report both the smallest and largest group in each string. If you average 8 or 10 of these results you will find that the average that the biggest groups exceed the smallest in the same string will be pretty close to 90%. It seems unlikely that the AR editors are all old and shaky or are shooting defective bullets. This variation occurs in the testing of pistols and inaccurate rifles as well as in the testing of ugly “tactical” rifles that sometimes shoot much better.
I think this little factoid is more that just idly interesting. It might be productive to think about this surprising and unavoidable variation in group sizes in relation to the common practice of finding optimum loads by shooting a one 5-shot, or even one 10-shot, group for each load being tested. Yes, 10-shot groups vary less but still a lot.
And because this variation seems to be independent of the quality of either the rifle or ammunition it is also worth thinking about in relation to fliers.
John
Think About It
- 3.7K Views
- Last Post 05 January 2016
Attached Files
John, You forgot Santa Claus and the Great Pumpkin.
B.E.Brickey
Attached Files
When you post Ken I am not only paying attention but have my pencil and notebook to write it down.
Yes some fliers fly INTO the center. That is why if you have a load that will average 1 moa and shoot some unbalanced bullets that deflect the bullet on average 0.2 moa, you do NOT get 1.2 moa groups but something much smaller as joe and mtngun have pointed out.
This is ONE of the reasons that defects don't have as bad an effect as we imagine.
OK no religious explanation for fliers but UFOs and the Easter Bunny are prime suspects.
John
Attached Files
ahem ... pay attention class .... about 2 years ago i clearly mumbled that ::
some fliers fly INTO the center .
as for other mysterious bullet behavior ::
remember :::: NO RELIGION DISCUSSIONS !!
ken
Attached Files
Joe, I agree completely that opinions are sometimes clothed in math or physics or worse. It is good to have your B. S. detector turned on.
Sorry for being unclear. i wasn't referring to Larry's 25 shot group which as you point out is just a normal group -- no bad bullets. Maybe the other target was never posted and he just sent it to me. He shot a few bullets with holes in one side orienting some defective bullets 180 degrees from the others along with some good bullets. The defective bullets landed on opposite sides and clearly out of the group of good bullets in the center. Hopefully pictures of that group will be on our website.
OK. I dismembered your test procedure. I will modify my guess as to why you didn't get a doughnut. If the metal removed was on only one side of the bullet, not enough metal was removed to “throw” them out far enough.
OK. I will try to shoot a doughnut if I can find a way to make a uniform defect, although i can't be sure of orientation in my bolt actions so the donut (if I get one) may be fat on one side.
John
Attached Files
Joe,
When you argue against physics (assuming the assumptions and calculations used are both correct) you have usually saddled the wrong horse.
Sometimes opinions are clothed in mathematics and/or physics to convince the less nerdlike.
Doughnuts can be shot with unbalanced bullets IF the rifle is accurate enough and the unbalancing (defect) is big enough -- if you rotate the position (1 to 12 o'clock) of the defects as it leaves the muzzle. Larry Landercasper (the guy with the 25 shot group I used in TFS #229) has done just that with his rimfire rifle. I believe it was posted on this forum back when he posted the 25 shot group but I am not sure. I have asked Mike to put his report on our website so it will be easily found in the future. He pretty much showed that Vaughn was right at least qualitative. (The direction of the deflections could be controlled by the position of the defect when the bullet leaves the muzzle.) I don't believe, but could be wrong, that he would claim that he confirmed that the equation predicts the amount of deflection because his defect making wasn't precise enough. My guess is that it could be proven.
I'm looking at Larry's group, and it doesn't look like a doughnut to me. Nor a cruller. It looks like a conventional randomly normal group. We went around on this before, I'm having deja vu. Or high blood sugar.
This isn't news, Mann showed that he could cause repeatable deflections in the same amount and direction by having the defect in the same position i.e. 12 o'clock 110 years ago (page 216-220 in “Bullets Flight"). I don't believe he attempted to quantify the deflection but he understood why it happened.
As you know, I've never been impressed by Mann's book-he should have stopped with the bone cutter and gone to Bermuda. His writing is as bad as Keynes's, and his sample sizes are tiny. In page 216-220, abut mutilated bullets:
Test 130, Aug. 11, 1903 12 shots
Test 131, Aug. 11, 1903 15, 8, 5, 5 = 33 shots
Test 132, Oct 13, 1902 9 shots
Test 133, Sept 6, 1902 8 shots
Test 134, May 20, 1903 8 shots
Test 135, Aug. 30, 1902 6 shots
Test 136, Sept. 6, 1902 5 shots
81 shots in ~ a year. I commonly shoot more shots than that on one trip to the range. And I'm frequently not sure the data from my shooting SUGGESTS anything, much less PROVES anything. Franklin didn't prove anything to me in these pages-but I was interested to see the Leopold's remark about “hollow groups".
I think the reason a doughnut didn't show up in your testing is that the dispersion of the defective bullets overlapped with the dispersion of the good bullets. If the load had been more accurate and/or the defects had been bigger I think you would have seen the doughnut. An easier test would be to just go for two groups or an eight shaped group by orienting all the defects the same way.
I can't find my many-shot non-doughnut-shaped group pictures, but there were NO good bullets shot. Try that 50 shot test RF in your tunnel.
John
Attached Files
If undamaged bullets shoot 1” groups, the damaged bullets should shoot outside or at the edge of a 1” circle. Damaged bullets should shoot doughnut-shaped groups. They don't. If anything, damaged bullets shoot what look like RANDOM NORMALLY distributed sets of shots, they look like BIGGER groups, they don't look like dougnut-shaped groups.
So, if equally-damaged bullets don't shoot doughnut-shaped groups, then dispersion ain't constant, and dispersion ain't in proportion to unbalance.
What this means is that we don't know what happens when we shoot a damaged bullet. Harold didn't know either. We can do physics and arithmetic at home all we want, but if the bullets don't follow the arithmetic, the arithmetic is wrong.
-The policeman's lament, no doughnuts.
Joe,
When you argue against physics (assuming the assumptions and calculations used are both correct) you have usually saddled the wrong horse.
Doughnuts can be shot with unbalanced bullets IF the rifle is accurate enough and the unbalancing (defect) is big enough -- if you rotate the position (1 to 12 o'clock) of the defects as it leaves the muzzle. Larry Landercasper (the guy with the 25 shot group I used in TFS #229) has done just that with his rimfire rifle. I believe it was posted on this forum back when he posted the 25 shot group but I am not sure. I have asked Mike to put his report on our website so it will be easily found in the future. He pretty much showed that Vaughn was right at least qualitative. (The direction of the deflections could be controlled by the position of the defect when the bullet leaves the muzzle.) I don't believe, but could be wrong, that he would claim that he confirmed that the equation predicts the amount of deflection because his defect making wasn't precise enough. My guess is that it could be proven.
This isn't news, Mann showed that he could cause repeatable deflections in the same amount and direction by having the defect in the same position i.e. 12 o'clock 110 years ago (page 216-220 in “Bullets Flight"). I don't believe he attempted to quantify the deflection but he understood why it happened. I think the reason a doughnut didn't show up in your testing is that the dispersion of the defective bullets overlapped with the dispersion of the good bullets. If the load had been more accurate and/or the defects had been bigger I think you would have seen the doughnut. An easier test would be to just go for two groups or an eight shaped group by orienting all the defects the same way.
John
Attached Files
Joe,
I'll work on some of that today, as it is still snowing like crazy here. 193.4 inches last month on the pass behind my house, a new record for a December, not a high snow month.
But I will only do it for 1st place and 2nd place, as who cares below that? I'm only interested in winners, not the losers down the list. What does it take to WIN? The rest of us down the line are just there to be social and make noise.
Ric:fireI'm interested in the ratios that are remarkably similar, 10 shot to 5 shot. If you send me the workbook, I'll work on it. If you can save it as an .xls workbook. I'm staying in today, it's 47 this morning, parka and mittens and wooly hats required. joe b.
Attached Files
Joe,
I'll work on some of that today, as it is still snowing like crazy here. 193.4 inches last month on the pass behind my house, a new record for a December, not a high snow month.
But I will only do it for 1st place and 2nd place, as who cares below that? I'm only interested in winners, not the losers down the list. What does it take to WIN? The rest of us down the line are just there to be social and make noise.
Ric:fire
Attached Files
OK, I give up! My memories of all the matches I lost by 0.020” are insignificant to the total matches I shot (I went back and counted.). So how competitive are the Issue class military rifles?
(For some reason this board will not let me post .xlsx “excel 2007” tables)
The chart below has the first column the year, the second is the 100 and 200 yard five shot group aggregates of the winner, the third the second place shooter and the last the MOA difference between first and second. The winner's MOA was 1.8787 and the difference to second place was 0.1629 larger. So the second place shooter's groups are only 1.0867 times larger than the winners, much less than regular benchrest results.
Ric; if you've got this info in EXCEL, please try this. I think your data got clumped.
For each year, for 100 then 200 yards, list the group sizes, first through 5th.
Calculate 2nd/1st, 3rd/1st, 4th/1st, 5th/1st for 100 and 200 yards
Do it for each year.
Average, for 100 yards, for all years:
2nd/1st
3rd/1st
4th/1st
5th/1st
Then average for 200 yards.
I'll bet a quarter that the results look like the numbers I got, above-at least for 100 yards.
Attached Files
Physics says that an unbalanced bullet will cause dispersion in proportion to RPM.
We need to figure out what our BIG sources of dispersion are and go after them first. That is what I hoped to determine with my water tank experiments. Physics never said that to me. Harold did a lot of “dry-labbing", he should have taken that 270 to the range more often. Damaged bullets are unbalanced bullets, and we'd suspect that the more unbalanced, the greater the dispersion. If we damage a batch of bullets, all the same, we'd suspect that when shot, the dispersion increase would be about the same. If undamaged bullets shoot 1” groups, the damaged bullets should shoot outside or at the edge of a 1” circle. Damaged bullets should shoot doughnut-shaped groups. They don't. If anything, damaged bullets shoot what look like RANDOM NORMALLY distributed sets of shots, they look like BIGGER groups, they don't look like dougnut-shaped groups. So, if equally-damaged bullets don't shoot doughnut-shaped groups, then dispersion ain't constant, and dispersion ain't in proportion to unbalance. What this means is that we don't know what happens when we shoot a damaged bullet. Harold didn't know either. We can do physics and arithmetic at home all we want, but if the bullets don't follow the arithmetic, the arithmetic is wrong. Prove it to yourself. Get a 22 RF rifle, a box of 50 ctgs, and a file. File relatively-big wedges, about the same size, about the same place, out of each bullet. Shoot them all, all 50, at a big target-aiming at the same point. Some bullets hit close to center, some hit way outside, it just looks like a big group. Then, while examining the target, ask yourself this question: If damaged bullets are unbalanced bullets, why did some of these bullets hit so close to center? The policeman's lament, no doughnuts.
Attached Files
OK, I give up! My memories of all the matches I lost by 0.020” are insignificant to the total matches I shot (I went back and counted.). So how competitive are the Issue class military rifles? (For some reason this board will not let me post .xlsx “excel 2007” tables) The chart below has the first column the year, the second is the 100 and 200 yard five shot group aggregates of the winner, the third the second place shooter and the last the MOA difference between first and second. The winner's MOA was 1.8787 and the difference to second place was 0.1629 larger. So the second place shooter's groups are only 1.0867 times larger than the winners, much less than regular benchrest results.
Attached Files
If matches are won by 0.010” that means matches are won by luck, though no doubt a lot of skill is required to shoot that consistently especially in wind and mirage.
Some matches may be won by a smidgin, but on average:
AVERAGE GROUP SIZE RATIOS CBA NATIONAL MATCH data for 2000 to 2013, HVY, PBB, PRO and UNR shows the following ratios of averages for 5 shot 100 yard groups: Shooter 2 / Shooter 1 1.20 Shooter 3 / Shooter 1 1.33 Shooter 4 / Shooter 1 1.47 Shooter 5 / Shooter 1 1.55 So Shooter 2 average group size is 1.2 times the size of Shooter 1 group size. I hadn't done the analysis on 10 shot 100 yard groups until this morning, 11/29/13, and was surprised to find their ratios to be: Shooter 2 / Shooter 1 1.21 Shooter 3 / Shooter 1 1.36 Shooter 4 / Shooter 1 1.50 Shooter 5 / Shooter 1 1.55 It appears that there's some underlying relationship causing these ratios to be almost identical. I wonder why. See “CBA NATIONAL MATCH 10 SHOT GROUP 12345.xls"
Attached Files
Ric, the reason I question the 0.010” or 0.020” claim is that mathematically speaking, lotsa luck proving that one load or one shooter is 0.010” more accurate than another. Can you even dope wind and mirage to 0.010"? I can't.
The top competitive shooters that I have been acquainted with were very consistent. They didn't shoot a perfect score every time, but they shot a good score every time, and they shot regularly. I on the other hand, have gone for years without firing a shot. It's sad how making a living and taking care of family sometimes interfere with the important things in life. :D :D :D
Tony Boyer said something in his book that impressed me -- that he actually prefers to practice on windy days when the rest of us stay home. He reasons that anyone can plunk down the money to buy a gun that is just as accurate as his gun, and shoot groups just as good as his under ideal conditions, but he believes he holds an edge in poor conditions. That is probably true for most competitive precision shooting?
Attached Files
John, Joe does an exceptional job of sharing and analyzing his shooting data, though I took issue with certain points his article made. Joe says you don't need mean radius because you can predict mean radius from group size, I counter that you can predict group size from mean radius, and with fewer shots, too. :D
But we all agree that rarely can something be “proved” wtih 5 shots, or 10 shots, or often not even with 25 shots, other to prove that a certain load is not going to shoot well.
Another pet peeve of mine is that people often claim to “prove” something without using a control. I.e., “I use a magic bullet design and I've proven it works, see here's this solitary group.” And I always wonder, “BUT COMPARED TO WHAT?” It's always more convincing if we include an “ole reliable” control load in our experiments, preferably loaded at the same time and shot on the same day. Yeah, that takes a lot of shooting and we don't always have time, even if we are willing.
In practice I often compare “this week's load” to “last week's load.” It's better than no comparison at all, but sometimes leaves me wondering “maybe the range conditions were better last week? Or maybe I was just having a bad day? Etc..” :D :D :D
Attached Files
Mtggun,
Looking at the last four years of National Matches, Military Rifle, Issue class, group scores I will stick with my “matches are won with 0.020” better groups. Mike Kastning won three years in a row because he was “lucky” for three years in a row? I don't think so, I think he beat the socks off the rest of us because he could shoot those 0.020” smaller groups more often than the rest of us.
Ric
Attached Files
My philosophy is this: if a load shoots really really really bad, you don't need a lot of shots to prove that it is bad. If it shoots a pattern instead of a group, you know it's a bad load.
But if you are trying to prove that one load is 10% better than another load, that's tough, and will take a lot of shooting to prove a statistically significant difference.
AMEN:
This has been explained several times in TFS in the last couple of years. And this past year in TFS #235 Joe presented a simple, easy to use, mathematical way to estimate how many groups are required to reach a reasonable conclusion that one load is better than another when the difference is 10%, 20%, etc. It is hard to believe that when one of two 10-shot groups comparing two loads is 20% better you only have the roughest guess and you need several more pairs to be reasonable sure that one load really is better. But that's the way it is.
Writers presenting accuracy results from one five or one ten shot group are giving the reader at best a rough estimate and possibly misleading information.
John
Attached Files
Mtngun,
I shoot about 920/940 shots sorting reloading dies for the 30/06. Therefor, I have no faith in 5 five shot groups. Since matches are won on 0.010” groups, or less variance, you better have good data before I have any faith in your results.If matches are won by 0.010” that means matches are won by luck, though no doubt a lot of skill is required to shoot that consistently especially in wind and mirage.
If you use Taran you can overlay your individual groups into one big group, Then it doesn't matter whether you shoot 2-shot groups or 10-shot groups, only that you fire enough shots. Example below of two 11 shot groups overlaid into one 22 shot group. Of course you don't need any fancy analysis to tell you that this is not a bragging size group. :D
Note Taran's “confidence meter” in the lower right corner. It takes a lot of shots to make Taran feel confident. :D
- #Permalink
- 0
- 0
Attached Files
Mtngun,
I shot about 920/940 shots sorting reloading dies for the 30/06 in 2006. Therefore, I have no faith in 5 five shot groups. Since matches are won on 0.010” groups, or less variance, you better have good data before I have any faith in anyone's results.
Ric
Attached Files
I have done quite a bit of this kind of testing without finding accuracy degradation for either weight variation or some very visible casting defects.
Physics says that an unbalanced bullet will cause dispersion in proportion to RPM. Try repeating your tests at 200,000 rpm ? :cool:
Harold Vaughn quantified this nicely in his book “Rifle Accuracy Facts." He actually built a device to measure the imbalance in bullets (not sure if his device would work with our cast bullets?). Even match grade jacketed bullets are imperfectly balanced, never mind our humble cast bullets.
HOWEVER Vaughn also pointed out that total dispersion is the square root of the sum of the squares of all the individual dispersions. What this means in practical terms is that if you totally eliminate one source of dispersion, like imbalance, overall dispersion may not improve much because all those other sources of dispersion are still there. And if the improvement is only 10%, lotsa luck proving it ! :D
We need to figure out what our BIG sources of dispersion are and go after them first. That is what I hoped to determine with my water tank experiments.
Attached Files
Categories
- All Categories
- General Polls
- Contact Us w/ Forum Issues
- Welcome to The Cast Bullet Association Forum
- General
- Bullet Casting
-
Guns and Shooting
- AR Platform
- TC Contenders & Other Single Shot Handguns
- Shotguns
- Informal Matches & Other Shooting Events
- Gunsmithing Tips
- Gun Cleaning & Maintenance
- Optics
- Benchrest Cast Bullet Shooting
- Military Bench Rest Cast Bullet Shooting
- Silhouette Shooting
- Postal Match Cast Bullet Shooting
- Factory Guns
- Black Powder Cartridge
- Hand Guns
- Lever Guns
- Single Shot Rifles
- Bolt Action Rifles
- Military Surplus Rifles
- Plinkers Hollow
- Muzzleloaders
- Hunting
- Reloading
- Buy, Sell or Trade
- Other Information & Reference
Search
This Weeks High Earners
-
Bryan Austin
21
-
fc60 20
-
Ed Harris
14
-
Bud Hyett
10
-
linoww
9
-
Aaron
8
-
sluggo
7
-
DanLH 5
-
RicinYakima
4
-
Wilderness
4
