# Groups tightening at longer ranges.



## longbow (Mar 31, 2009)

Here's something that I've noticed about shooting short range vs long range. I wonder if DallonC or one you others can explain it to me.

I've seen this with several of my guns and others have told me they've seen it too. I have guns that shoot 3/4 - 1 moa groups at 100, 200 and 300. When I get past that the groups start to tighten up moa-wise not inch-wise. I can be shooting 1 moa at 100 and be shooting ~1/2 moa at 600++. I know the bullet "goes to sleep" or "stabilizes" after a while but if your "dispersing" bullets at 1 moa why wouldn't it be the same all the way to as far as your shooting. 
I'm not seeing things, me and my friends have noticed the same thing. We just can't make any sense of it.


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## hyperduc (Sep 18, 2009)

Okay, rather simple explanation.

You already know the bullet leaves the barrel spinning, but it doesn't spin exactly around the center of its mass, rather it spins around what could be most easily described as an orbital axis.

Ideally that axis is the bore of the barrel, as that bullet spins around that axis it does so in ever smaller concentric circles. And as the bullet travels further away from the barrel those circles become smaller, which explains the tighter grouping at distance. Most bullets stabilize quickly enough that the aforementioned phenomenon isn't observed.

The dimensions we are talking about here are only fractions of an inch.

The attached image (sorry I was in a hurry) should help.


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## DallanC (Jan 13, 2009)

I've heard of 2 other cases of this... indeed it sounds quite bizzare! 

I cant explain it, but offer a theory. You are dead on to think that if its dispersing at 1MOA that would continue over time and not constrict. The only thing I can think of is the rounds aren't stabilized and as they turn "out of round" through the air it is having some form of corkscrewing effect that diminishes over time. Really though, its a total guess. It would require all bullets to have a very very tiny standard deviation in velocity for them to all "settle in" at precisely the same point, extremely long odds indeed!

Couple questions... are your target holes at 50yds, 100, 150, 200 etc perfectly round? Or slightly out of round? That would indicate stability issues. What were wind conditions? Any turbulance from muzzle to target?

It seems like a gun that shoots that way consistantly could win the owner some $$$ at the ranges :twisted: 

-DallanC


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## DallanC (Jan 13, 2009)

Hey hyperduc snuck in his post while I was typing up mine.

Yea using his picture, thats my guess. A corkscrew effect would be due to the bullet wobbling out of round (imagine the bullet rotating, it rotates along the main axis perfectly in the center, but the tip and base of the bullet are offset from the main axis. It will "plane" in the air according to whichever direction the tip is pointed but as the bullet stabilizes that direction diminishes over time resulting in the picture hyperduc posted.

Generally though multiple bullets with this behavior dont stabilize at the same rate and hit at the same location resulting in even wider groups, not smaller. Its pretty remarkable you seem to have one of those rare loads that stabilize at the same rate, rotational angle and distance.

Again to verify, check paper holes at evert 50 yards to see how out of round the bullet is when its passing through at those ranges. Nice small holes = stabilization. Oblong holes = corkscrewing bullets. A hole that looks like your bullet = keyhole :wink: 


-DallanC


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## DallanC (Jan 13, 2009)

Heres an article with more info I just found:

www.frfrogspad.com/extbal.htm

Computed bullet flight path and stabilization:










-DallanC


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## longbow (Mar 31, 2009)

That seems quite bazare to me even thogh it makes sense. The corckscrewing of the bullet until it "goes to sleep" is what causes the group to settle down after 300 or 400 yards. Kind of like a wobbling football. Very interesting. Thanks guys. Chuck.


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## Frisco Pete (Sep 22, 2007)

Hundred of years ago in central Europe, gunmakers invented the rifled bore. Many rifleman of that day said that the reason it works is that there are little imps, or devils that ride on the bullet and cause it to miss, but the addition of rifling causes them to be thrown off at one point or another.

Now I know that we have advanced scientifically from those old German and Swiss gunmakers, but there are times when I think that you have to wait past 100 yards for those gremlins to be tossed off the bullet is as good of an explanation as any.

I certainly know that some of my reloads (and factory ammo) that I had such high accuracy hopes for that turned out to be disappointing on paper probably was just infested with little devils that misguided the bullet and refused to be tossed off :wink:


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## longbow (Mar 31, 2009)

Thanks hyperduc, DallonC, FriscoPete. I'm sure I'll have more questions and maybe be able to answer some questions in the future.


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## Al Hansen (Sep 7, 2007)

DallanC said:


> Heres an article with more info I just found:
> 
> http://www.frfrogspad.com/extbal.htm
> 
> ...


That must be out of a Remington. Buy a Savage next time. They don't come with Gremlins. :lol: -O|o-


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## DallanC (Jan 13, 2009)

I have one, they are indeed accurate... at least for the first year or two, after that they are rusting as bad as a mid 60's Ford Falcon. Great accuracy, worst finish / blueing on the market :lol: 


-DallanC


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## jungle (May 10, 2008)

One thing I notice is that when I practice at 400 yards, 500 yards etc... any glitches in your shooting technique becomes amplified. And so I really discipline myself alot more at longer ranges "bearing down" and "following through" etc....

As a result my groups tighten up when I go back to 100 yards.


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## longbow (Mar 31, 2009)

I agree with that jungle. I tend to bear down a little more at longer ranges too. That might have something to do with it.


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## Bax* (Dec 14, 2008)

Would you guys mind briefly explaining MOA for me? I know it means Minute of Angle, but I have never understood how it is measured. EX) a rifle claims to shoot 1 MOA or better. What does that mean?

All I know is that I want TIGHT groups, and if they arent tight, I'm not happy


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## Chaser (Sep 28, 2007)

From what I understand, MOA means a 3 shot group that is less than an inch in diameter. Distances for MOA vary depending on how accurate your rifle is. Some can only drop MOA groups at 50 yards, and others can do it out to 300+. Am I right, guys?


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## Chaser (Sep 28, 2007)

Found this after my last post:
http://en.wikipedia.org/wiki/Minute_of_Angle


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## longbow (Mar 31, 2009)

Most shooters think of moa as 1" at 100 yard but like wickipedia say it's really 1.047. If you use milradians like alot of shooters do, it's 6.3 inches at 100 yards. Using the mill-dot system is great for rangefinding. I've used it for years and it works great.


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