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Old May 26, 2019, 10:46 AM   #1
Bart B.
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Do Test Groups' MOA Size Change With Range?

If the 100 yard 10 shot group is 1 MOA, will groups at greater ranges be the same?
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Old May 26, 2019, 10:51 AM   #2
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Yes, 1 MOA is approx. 1" at 100 yards and therefore 1 MOA at 200 yards is approx. 2". It's the old angle of the dangle thing.. LOL..
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Old May 26, 2019, 10:57 AM   #3
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NO

Quote:
If the 100 yard 10 shot group is 1 MOA, will groups at greater ranges be the same?
General rule, is; Likely not to NO or at least don't expect it. There are just too many variables. I have ever seen bullets, in flight and wonder how I get the good groups, I do …

Be Safe !!!
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Old May 26, 2019, 12:21 PM   #4
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They certainly can. Will they in your rifle with this ammo or that ammo? Maybe, maybe not. You have to test it before you can know.
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Old May 26, 2019, 12:24 PM   #5
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"If the 100 yard 10 shot group is 1 MOA, will groups at greater ranges be the same?"
Maybe or NOT. The longer distances may challenge sighting capabilities(optic magnification, visual acuity) or increase environmental issues.
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Old May 26, 2019, 12:27 PM   #6
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Quote:
Originally Posted by LineStretcher View Post
Yes, 1 MOA is approx. 1" at 100 yards and therefore 1 MOA at 200 yards is approx. 2". It's the old angle of the dangle thing.. LOL..
Exact trig value below was calculated to 102 decimal places for those wanting more precision:

1.04719753642832854694747069666400334739860873986429
830552235157457471965151538005004775737357536725837... inches at 100 yards.

Exactly one inch is good enough for the National Shooting Sports Foundation.
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Old May 26, 2019, 12:41 PM   #7
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In general usage, MOA is one inch per hundred yards. 1" at 100, 2" at 200, 10" at 1,000 yds.

A 1" group is MOA at 100yds, but 1/2" MOA at 200 yards.
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Old May 26, 2019, 02:47 PM   #8
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I know Bart cites "compensation" which works when barrel vibrations are just right to launch a low velocity bullet at a higher angle than a high velocity bullet, letting them both land close together at extended range, therefore a source of the converging bullet phenomenon. The Brits knew about that when they still shot the .303 at targets. Seems to me this would also mean that they were farther apart at midrange than the base group or the final group.

But I think more of us would experience the "trumpet effect" where other variables cause groups to widen more than the short range angular.
A pistol shooter opined that 25 yard groups do not scale up to 50 yards where the NRA shoots, that a 2.4X factor was closer to observations.

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Old May 26, 2019, 03:20 PM   #9
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Holy Carp Batman, talk about over thinking something... LOL..
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Old May 26, 2019, 03:42 PM   #10
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Not if you are a serious target shooter like Bart.
Or have an idle Sunday like me.
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Old May 26, 2019, 03:53 PM   #11
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Calm conditions or with Wind and is it varying?
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Old May 26, 2019, 04:11 PM   #12
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Calm conditions or with Wind and is it varying?
Calm conditions but a 30 fps spread in muzzle velocity.
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Old May 26, 2019, 04:53 PM   #13
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You can shoot small group in practice but what counts is at match. Ask Bart he should know. Tell everyone how it felt to shoot next to last in biggest match as team member and that in the books. You couldn't pull off what your posting about.
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Old May 26, 2019, 05:07 PM   #14
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Originally Posted by old roper View Post
You can shoot small group in practice but what counts is at match. Ask Bart he should know. Tell everyone how it felt to shoot next to last in biggest match as team member and that in the books. You couldn't pull off what your posting about.
It felt good calling every shot center using wind corrections from the coach during the worst wind conditions ever shot in the match. We used between 20 and 35 MOA sight settings from windage zero. My job was to fire each shot aimed at bullseye center, I did that.

All of which is beyond comprehension by n'er-do-wells who don't grasp the subject posted. Someone always shoots the low scores in team matches and such has nothing to do with exterior and interior ballistic variables' effects on bullet trajectories.
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Old May 26, 2019, 07:13 PM   #15
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Contrary to popular belief, bullets don't travel in a perfectly straight line, but in a spiral, due to imperfections and precession, like a top tends to travel in a spiral.

This precession has been plotted by installing perfectly-aligned targets out to several hundred yards, then shooting at the closest one and measuring where that bullet (or several bullets) impact subsequent targets, (accounting for drop).

Bullets also tend to "go to sleep" at some point in flight and the precession decreases.

A bullet's spiral is not huge and better bullets travel in tighter spirals than poor bullets or those that have impacted twigs, etc.

You can choose not to believe this and I won't be angry (but it's true).
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Old May 26, 2019, 08:28 PM   #16
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Originally Posted by Picher View Post
Contrary to popular belief, bullets don't travel in a perfectly straight line, but in a spiral, due to imperfections and precession, like a top tends to travel in a spiral.
What is the spiral sizes in MOA at 100, 200 and 300 yards with the best, most uniform bullets?
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Old May 26, 2019, 09:08 PM   #17
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MOA increases with flight time, or range. The culprit is gravity.

When stating group size in MOA, it is generally assumed range of 100yd, or specified otherwise. That's what I do.

-TL

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Old May 26, 2019, 09:11 PM   #18
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Picher is right on , bullets do not travel in a liner path . They are rotating around the straight path , that is why groups are round . There are many factors that will change the figures and ranges some what , but a good rule of thumb is 1 at 100 , 2.8 at 200 and 4.5 at 300 yards . After that the bullet does start to settle and the group sizes will start to get smaller percentage wise . There are many factors that will move the scale up or down . National bench rest champion shooters shoot 2.8x larger at 200 yards that 100 . If you do not then there is something wrong with your 100 yard load or you should be teaching the champs how to do it .
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Old May 26, 2019, 10:05 PM   #19
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Originally Posted by ernie8 View Post
Picher is right on , bullets do not travel in a liner path . They are rotating around the straight path , that is why groups are round.
If you shoot a couple hundred shots in a group, will most be in the outer third of its diameter?
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Old May 26, 2019, 11:02 PM   #20
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The outer third comprises about 55percent of the area of a circle. Assuming random dispersion, then yes. My limited observations are, however, that in a larger number of shots, most are clustered closer to the center of the group.

Last edited by Colorado Redneck; May 26, 2019 at 11:11 PM.
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Old May 27, 2019, 09:07 AM   #21
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Originally Posted by Colorado Redneck View Post
The outer third comprises about 55percent of the area of a circle. Assuming random dispersion, then yes. My limited observations are, however, that in a larger number of shots, most are clustered closer to the center of the group.
My data from analyzing such groups is...

40% of the shots are inside the inner 40% of group diameter. 30% in the next 30%, same for next 20% and 10%. Tracks well with statistical distribution curves.

Why are tuners used at the muzzle on some rifles? What do they change?
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Old May 27, 2019, 12:45 PM   #22
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A 10 shot group being 1 MOA is kind of miraculous by itself. However, if the question is will the same ammo and rifle produce 1" at 200 or 300 yards, then no.
"...and precession..." That's normally called pitching and yawing. The base of the bullet literally wobbles until the rifling twist takes effect and the bullet stabilizes. That's at around 300 yards for a .30 calibre.
Arrows do the same thing. You can see an arrow stabilize when the fletching kicks in. It's like a switch was thrown. The arrow's back end stops wobbling and starts flying true.
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Old May 27, 2019, 02:10 PM   #23
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The longer the bullet is out of the bore, the more opportunity things like wind and gravity have to change the path of the bullet. Therefore, with sufficient sample sizes, (i.e. enough groups shot and compared) the MOA measurement of groups at longer ranges should be larger than groups shot at shorter ranges under identical conditions. Maybe not a lot bigger, but some.

There are some circumstances under which a rifle might, under nearly ideal conditions, make groups that are about the same, measured in MOA at one particular farther range, but that's sort of a pathological case. Still interesting to consider.
Quote:
Exactly one inch is good enough for the National Shooting Sports Foundation.
https://www.nssf.org/shooting/minute-angle-moa/
"A MOA is 1/60th of a degree.

1 MOA spreads about 1″ per 100 yards. (actually 1.047″)"
Approximating 1MOA as 1" results in an approximation error of about 5%. Not a big error. For reference, here are some other approximations that are about the same in magnitude:
  • Using 3 instead of the correct value for pi.
  • Approximating 100 yards as 95.5 yards.
  • Approximating a minute of angle as being 1/63rd of a degree instead of 1/60th of a degree.
In practice, a 5% approximation error is not a big deal given that there's probably around that much error in the actual group size measurements before one starts calculating the MOA values. And, of course, if everyone is using the same approximation by standard, then it's not an issue at all.
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Old May 27, 2019, 03:14 PM   #24
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Quote:
Originally Posted by T. O'Heir View Post
The base of the bullet literally wobbles until the rifling twist takes effect and the bullet stabilizes. That's at around 300 yards for a .30 calibre.
Then why do the best 30 caliber match bullets test .20 MOA at 100 yards, .25 MOA at 200 or .30 MOA at 300? I've seen 30 caliber match bullet test groups shot at Sierra's 100 yard range in California averaging 1/10th inch.

Benchrest aggregate group average records expand about the same from 100 to 300 yards. Their single 5 and 10 shot group records are smaller.
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Old May 27, 2019, 06:43 PM   #25
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Bench rest reported groups are factored from 100 to 200 yards , that is not the actual 200 yard measure . If you are shooting .10 groups with a factory mass produced bullet , .30 cal yet , you should go and win some side bets at a bench rest match . I am just glad all the super shooters do not shoot in matches , or I would be in trouble . Kind of like when I was running a pro class drag car in NHRA , people who built their motors with parts from Auto Zone told me how they were making more hp than my factory backed motors were . All my time wasted with blocks not even released to the public , flowed heads and handmade sheet metal intakes made to match , custom turned cam ,750 cfm carbs flowed to 1180 . In case there are any racers here , 314 sb chevy , 7.82 at 178.4 best at 11,500 rpm shift and a 7500 launch .
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