help me get my head around this...

georgehwbush · March 10, 2024, 11:52 AM

shooting 243win for years now and while not a competitor i shoot pretty good, but of late; I have been shooting 100yd groups in the .75" range, but at 200yds they open up to 3.75" that's a five fold increase in size at only twice the distance. and it's radial not horizontal. what could be causing this? (ar-10, 243win, 24" ss barrel, handloads [107gr smk, 42.7gr alliant reloader 19, winchester brass, cci 200 primers]) one could extrapolate that it would be eighteen and three quarter inches at four houndred yards... "it isn't though" it's only a little over 4" at 425 yards. so how can it be so "crappy" at 200 ?

tangolima · March 10, 2024, 12:07 PM

What does the group at 200yd look like? Radial means vertical stringing? How many shots in the groups?

Any wind changes among 0-100yd, 100-400yd?

-TL

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**JohnKSa** · March 10, 2024, 01:09 PM

Sometimes if a bullet is marginally stabilized, it will shoot well at closer ranges but groups will open as the bullet destabilizes.

One possibility, I guess.

stagpanther · March 10, 2024, 01:10 PM

That scenario looks very unlikely to me--either you or your target got unbalanced at the 200 yd mark?

tangolima · March 10, 2024, 01:48 PM

When met with cross wind, a bullet will settle in a new pitch and yaw angles to counter its effect. Before it settles, the nose of the bullet rotates in a circle/ellipse around its final position, and the bullet moves forward in a corkscrew manner. This is called nutation.

If there is strong cross wind between 100yd and 200yd, the bullet nutates again. If nutation hasn't been dampened when the bullet reaches 200yd target, the group opens. By the time it gets to 400yd, the nutation is gone assuming no wind changes, and the group tightens again.

Shooting long range is full of uncertainties, as there is always disturbances in the air mass the bullet travels through.

Even without such disturbances, groups in moa degrades with distance. My rule of thumb is 10% every 100yd. For instance, if I shoot 1moa (1") at 100yd, I expect 1.3moa (3.9") at 300yd.

Just a thought.

-TL

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georgehwbush · March 10, 2024, 03:52 PM

tangolama the range is sheltered from the wind for about the first 80 yards. and there was a crosswind of about 6knots. i hadn't thought of that as causing the dispersion issue. but yes that's a vary good call.

that would explain the fact that 425 is no wider than 200 i like your answer. gives me something to work on.

georgehwbush · March 10, 2024, 03:55 PM

sorry for the misspelling. just a thought, i don't think of quarter mile as long range. half mile on the other hand....

tangolima · March 10, 2024, 04:17 PM

Quote:

Originally Posted by georgehwbush

sorry for the misspelling. just a thought, i don't think of quarter mile as long range. half mile on the other hand....

It is all relative. Size of target plays key role. People shooting long range long range (>500yd?) are trying to hit larger targets, torso sized or bigger. Shorter range with smaller target makes it almost as challenging, if not more.

Where I live shooting beyond 300yd is way more costly. My method of training is soda can at 150yd with .22lr, or lately clay ducks at 110yd with .25 cal airgun. All outdoor in the wind mind you. It ain't easy.

-TL

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georgehwbush · March 10, 2024, 04:23 PM

tangolima yeah, soda cans at 440 for me with 243. my 22lr is good out to about 170 and then degrades very quickly.

just reread this thread, to answer your Q. 'Radial means vertical stringing?' no by radial i meant "all the way around the point of aim."

but the wind is a unknown variable in all shooting, sometimes we guess "calculate with all the information we have" real close, and some times it blind sides us. it's definitely the loose cannon on deck.

and i do think you are right about that being what i was seeing happen.

tangolima · March 10, 2024, 04:33 PM

Quite right. We do the best to calculate for the first shot hit. I allow myself for a quick 2nd follow up shot and no more. Then I have to wait a minute to try again. That way I force myself to read the wind more accurately.

I also have a ar-10 in .243. Accuracy is so so. Hovering around 1-1.5" at 100yd. Will take it out to 300yd once I receive the new order of 6mm bullets.

Yeah radial means all around. Didn't think of that for some reason when I was typing.

-TL

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March 10, 2024, 11:52 AM	#1
georgehwbush Senior Member Join Date: July 14, 2023 Location: down town USA Posts: 168	help me get my head around this... shooting 243win for years now and while not a competitor i shoot pretty good, but of late; I have been shooting 100yd groups in the .75" range, but at 200yds they open up to 3.75" that's a five fold increase in size at only twice the distance. and it's radial not horizontal. what could be causing this? (ar-10, 243win, 24" ss barrel, handloads [107gr smk, 42.7gr alliant reloader 19, winchester brass, cci 200 primers]) one could extrapolate that it would be eighteen and three quarter inches at four houndred yards... "it isn't though" it's only a little over 4" at 425 yards. so how can it be so "crappy" at 200 ?

March 10, 2024, 12:07 PM	#2
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,834	What does the group at 200yd look like? Radial means vertical stringing? How many shots in the groups? Any wind changes among 0-100yd, 100-400yd? -TL Sent from my SM-N960U using Tapatalk Last edited by tangolima; March 10, 2024 at 12:21 PM.

March 10, 2024, 01:09 PM	#3
JohnKSa Staff Join Date: February 12, 2001 Location: DFW Area Posts: 25,002	Sometimes if a bullet is marginally stabilized, it will shoot well at closer ranges but groups will open as the bullet destabilizes. One possibility, I guess. __________________ Do you know about the TEXAS State Rifle Association?

March 10, 2024, 01:10 PM	#4
stagpanther Senior Member Join Date: March 2, 2014 Posts: 11,805	That scenario looks very unlikely to me--either you or your target got unbalanced at the 200 yd mark? __________________ "Everyone speaks gun."--Robert O'Neill *I am NOT an expert--I do not have any formal experience or certification in firearms use or testing; use any information I post at your own risk!*

March 10, 2024, 03:52 PM	#6
georgehwbush Senior Member Join Date: July 14, 2023 Location: down town USA Posts: 168	that makes sense tangolama the range is sheltered from the wind for about the first 80 yards. and there was a crosswind of about 6knots. i hadn't thought of that as causing the dispersion issue. but yes that's a vary good call. that would explain the fact that 425 is no wider than 200 i like your answer. gives me something to work on.

March 10, 2024, 01:48 PM	#5
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,834	When met with cross wind, a bullet will settle in a new pitch and yaw angles to counter its effect. Before it settles, the nose of the bullet rotates in a circle/ellipse around its final position, and the bullet moves forward in a corkscrew manner. This is called nutation. If there is strong cross wind between 100yd and 200yd, the bullet nutates again. If nutation hasn't been dampened when the bullet reaches 200yd target, the group opens. By the time it gets to 400yd, the nutation is gone assuming no wind changes, and the group tightens again. Shooting long range is full of uncertainties, as there is always disturbances in the air mass the bullet travels through. Even without such disturbances, groups in moa degrades with distance. My rule of thumb is 10% every 100yd. For instance, if I shoot 1moa (1") at 100yd, I expect 1.3moa (3.9") at 300yd. Just a thought. -TL Sent from my SM-N960U using Tapatalk

March 10, 2024, 03:55 PM	#7
georgehwbush Senior Member Join Date: July 14, 2023 Location: down town USA Posts: 168	sorry for the misspelling. just a thought, i don't think of quarter mile as long range. half mile on the other hand....

March 10, 2024, 04:23 PM	#9
georgehwbush Senior Member Join Date: July 14, 2023 Location: down town USA Posts: 168	tangolima yeah, soda cans at 440 for me with 243. my 22lr is good out to about 170 and then degrades very quickly. just reread this thread, to answer your Q. 'Radial means vertical stringing?' no by radial i meant "all the way around the point of aim." but the wind is a unknown variable in all shooting, sometimes we guess "calculate with all the information we have" real close, and some times it blind sides us. it's definitely the loose cannon on deck. and i do think you are right about that being what i was seeing happen.

March 10, 2024, 04:33 PM	#10
tangolima Senior Member Join Date: September 28, 2013 Posts: 3,834	Quite right. We do the best to calculate for the first shot hit. I allow myself for a quick 2nd follow up shot and no more. Then I have to wait a minute to try again. That way I force myself to read the wind more accurately. I also have a ar-10 in .243. Accuracy is so so. Hovering around 1-1.5" at 100yd. Will take it out to 300yd once I receive the new order of 6mm bullets. Yeah radial means all around. Didn't think of that for some reason when I was typing. -TL Sent from my SM-N960U using Tapatalk