Medium distance shooting


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kestak
October 4, 2013, 10:05 AM
Greetings,

I have been shooting up to 700 yards with different calibers and here I have no answer.

I shot a CAR-15 with ACIG. Mounted on it. It is a horseshoe with dot in center. 1:9 twist.
Wind 7 miles per hour left to right.
75 degrees. Sunny.
55 grains soft point Hornady at around 3000 ft/sec.

15 rounds groups:
Dead center at 100 yards. Group size 1". I used the top of dot.
Dead center at 200 yards. Group size 3". I used center of dot (centered on target)
300 yards: used the top of line. Group is 6" to the right.
300 yards: used the top of the dot. Group is 3" low and still 6 inches to the right.

I cannot believe it is the wind that does that significant lateral movement. Is it?

Thank you

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rule303
October 4, 2013, 10:14 AM
It is quite possible. Who's to know what the wind conditions are 200 or 250 yards from your shooting position? Was that your only shooting session with those results?

taliv
October 4, 2013, 10:21 AM
the symptom sounds more like the sight is canted, which would cause both lower elevation and windage issues. any chance you're pushing the gun over due to position? or that the sight is actually mounted other than plumb?

kestak
October 4, 2013, 12:14 PM
Wind was constant. I walked a few times the distance. We are not talking about 600 or 800 yards but just 300. I plan to try again in a few days. I am not even cleaning the rifle to make sure nothing changes.

It is an ACOG mounted directly on the upper. If the sight was canted, would have it showed a little bit at 200 instead to be dead center? I just verified the rifle with a set of buble levers. Everything seems aligned. I already shot up to 600 yards with that same rifle with no problem.

Caliper_RWVA
October 4, 2013, 01:27 PM
Wind 7 miles per hour left to right.


I cannot believe it is the wind that does that significant lateral movement. Is it?



Yes, wind is important at 300yd.

At Appleseed, we will use a rough estimation of wind drift at 1 MOA per 100 yd per 10 mph. Keep in mind, this is a quick field estimation that will get you on target with common calibers, but also doesn't require a ballistic calculator or any calculator for that matter.

So, for a 7mph wind at 300 yd that would be 0.7 x 3 = 2.1 MOA of drift. 2.1 moa @ 300yd = 6.3".

kestak
October 4, 2013, 02:15 PM
Caliper,

Lol, I am a red hat (shoot boss too) in GA. I thought the Sunday long distance part a few times. And did the GA KD twice(it was a lot of fun) with KD AQT score of 219 and 5/5 at the 500 steel (yeah, I gotta brag, so all my fellow instructors now reading that thread gotta do their state KD and shove a better score to my face ;-). ).

That function is for 30 cal. It is taken from the WWII Garand function : distance x wind speed/1000= number of clicks (or MOA). And frankly, up to 300 included, I never had to adjust really for wind with my 308 with Sierra 2200 bullets because the drift was not significant. However, this is 223. Why no windage change at 200 but at 300 i have 6 inches deviation? Ot is why I am so puzzled.

P.s.: sorry guys for the little inside joke, but oh well, you want to get it, join us, we are not a close club like the Illuminati...hehehehe

C-grunt
October 4, 2013, 02:50 PM
I could definitely see that being wind. Especially if you are using 55 grn FMJs.

Also could be compounded on the rifle not being perfectly sighted in at 100. Being a half inch or so off to the right is going to be hard to see using a 3 or 4 power scope.

Caliper_RWVA
October 5, 2013, 11:17 AM
Kestak,
Congrats on the KD AQT! We've done a few KD events here in MI also. Great fun and I've got the full distance Rifleman patch too. Didn't have 500yd steel to shoot, but we did get a chance to shoot on a 300yd popup range. Tremendous fun! :D

Back OT, the wind formula may have been developed with the M1, but it works sufficiently well with 223. When I put the numbers into my ballistic app, the 223 does drift more than the formula, but the error only exceeds 1moa at 400yd. Not bad, it'll keep you on steel anyways. "Don't let perfect be the enemy of good enough" ;)

Not sure why you didn't see the effects at 200yd. Wind can do strange things though. That's why I found it the most exciting part of shooting at distance! A 7mph wind at 200yd calculates to 2.8" drift so less than half what you'd see at 300yd. Perhaps the wind downrange wasn't as constant as you thought?

35 Whelen
October 5, 2013, 11:32 AM
According to a ballistic calculator, the bullet you're using at said velocity, fired at 1500' above sea level in a 7 mph 90 crosswind will drift 9.03".
35W

kestak
October 5, 2013, 11:54 AM
Wednesday I am doing again the experiment. I plan to shoot three bullets: hornady sp 55 gr, hornady amax 55 gr and ss102 62 grains.

Thanks to you inputs guys, I now put doubt on me.

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