sighting in a rifle?


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bluecowdawg
June 19, 2003, 12:27 PM
o.k. here goes, i cant remember where i read this but it said that if you sight in a .223 to hit dead on at 25yrds it would also be close to dead on within an inch or so at 250yrds,which would be good enough for hunting purposes. now does anyone know if this is true or not and if it is is there a chart or something that i can find that shows other calibers, mainly for me a 30-30 , that i could sight it in at a short distance and also be on target at a longer distance?:confused:

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TallPine
June 19, 2003, 01:21 PM
Well, there are always two "zeroes" on every trajectory - that is, two points where the bullets arc crosses the line of sight, one rising and one falling.

The scope is considerably above the bore, so in the initial feet of the bullet path, it is well below the aiming point/line of sight.

Every cartridge will be different, according to its ballistics. There are charts that show the bullet drop, but not usually for short distances like 25 yards.

Assuming a zero at 25 yds, a .223 is going to have its second zero much farther out there than, say a 30-30, because the .223 is so much faster and aerodynamic.

But since you would typically shoot a .223 at longer ranges than a 30-30, the 25 yard zero might work out just about right.

Still, you ought to do a verification shot or two at longer ranges, but the 25 yard zero is handy for getting a new gun and/or scope "on the paper".

CZ-100
June 19, 2003, 01:30 PM
if I remember correctly .223 @ 25 meters is the same 300 meters

treeprof
June 19, 2003, 02:00 PM
Try here, bottom of the page:

http://groups.msn.com/TheMarylandAR15ShootersSite/zeroingmethods.msnw

Even if you're not shooting an AR, you can probably adapt the info for your needs (e.g. adjust for sigth ht over bore, etc.). It's pretty close for the 20" AR, less so for a 16" IME.

dakotasin
June 19, 2003, 05:28 PM
keep in mind that very few factory rifles have their base mounting holes in a perfectly straight line to the bore. this means you will need to compensate some for windage. how much depends on how much your equipment is out of line, which also includes scope canting.

hksw
June 19, 2003, 06:17 PM
Scope/sight height from the bore will also play a role.

hps1
June 19, 2003, 06:59 PM
Give this link a try. You can calculate any cartridge, sight height, etc.
As dakotasin said, however, none of the ballistic charts or calculators are 100 %; you still need to take it to the range and verify the settings.


http://www.norma.cc/htm_files/javapagee.htm

Regards,
hps

Art Eatman
June 19, 2003, 09:09 PM
bcd, that's pretty close, but I wouldn't sight in at 25 yards and feel secure at a hit out beyond 100 or so. The 25-yard deal is great to ensure you're on the paper at 100 yards, where you can get a better point of aim and impact.

At 100 yards, about 1-1/2 inches high is then right at dead-on at 200, and about five inches low at 300.

Art

bluecowdawg
June 20, 2003, 02:45 AM
At 100 yards, about 1-1/2 inches high is then right at dead-on at 200, and about five inches low at 300.



i forgot to mention,and i guess this is important, i am talking about sighting in with just the iron sights, no scope. anyhow, is what you stated above for a 30-30?

Art Eatman
June 20, 2003, 10:00 AM
The numbers I gave assumed a scope, and the .223. With my old eyes, it's been many a decade since I used iron sights. My numbers, then, wouldn't be exact, but they'd certainly be close enough to get started. Test-shots at various distances for your own rifle will do you the most good. And write down what you find out.

The trajectory of a .30-30 is more of a basketball arc than it is a football. :) With a scope, I'd figure two to three inches high at 100 to be dead on around 150-175. Beyond 200, range estimation becomes very important.

Dunno what sort of range facilities are available to you, but I've found that padding the window-sill of a car and leaning my shoulder into the back of the seat make a fair equivalent to a benchrest.

Art

treeprof
June 20, 2003, 10:29 AM
Sorry, I answered a question for a caliber you didn't ask about.

Art Eatman
June 20, 2003, 02:37 PM
I have found that a perfect zero at 25 yards can still be an inch or so to one side or the other at 100 yards. For 50- to 150-yard deer hunting, this doesn't matter.

With a scope, regardless of the cartridge, a perfect zero at 25 yards will be--generally--about two or three inches high at 100 yards. For deer hunting, this doesn't matter very much in the 50- to 150-yard ranges. I'm guessing that with iron sights you wouldn't be quite as high at 100 yards.

Which is why a heart/lung point of aim on Bambi is so effective. Large kill zone.

Art

stevelyn
June 21, 2003, 10:01 AM
The military typically has the troops do their zeroing at 25 meters on a 25 meter zero target. The goal is to shoot a 3-shot group inside a 4 centimeter circle.
A 25 meter zero or battle sight zero roughly works out to being dead on at 250 meters (2nd crossing of LOS) and about 2 1/2 to 3 inches low at 300 meters. Inconsequential when you consider the target is a mansize sillouette being engaged with open sights and you are shooting COM. Whether a sucking chest wound or gutshot both are going to hurt and mess up someone's medical records.
I can say it works for the .223 whether it's an AR or a Mini-14. However once you get it on paper you still need to take it out and shoot it at actual measured ranges to fine tune it. Set up targets at 100, 150, 200, 250, and 300 yrds or meters and shoot holding the same sight picture on each. Record where your groups strike relative to point of aim at each range and you'll know the trajectory of your bullet at those ranges.

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