Assistance on zeroing


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rhtwist
June 4, 2009, 10:25 AM
Hello,
I have a 7.62X39mm WASR and I looked at the ballistic table for Remington jhp ammo and it said that I should be hitting .1" low at 25 yards(my current range length) to get it good out to I believe 250 yards. Any opinions or advise on this measurement will be greatly appreciated.
rhtwist

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schlockinz
June 4, 2009, 11:28 AM
I've become a fan of the zero at 25 shot at 200, I sighted in 2" high at 25, and was still nailing the target reliably at 300 yds with no intermediate ranges used.

Deus Machina
June 4, 2009, 11:32 AM
Schlockinz's advice sounds about right.

Remember that your sights aren't likely to follow the ballistics, because they're so high above the bore.

Just measure and compensate.

rhtwist
June 4, 2009, 11:35 AM
Thanks Gentlemen,
But I'm getting out of my depth with measure and compensate, or just misunderstanding.
rhtwist

schlockinz
June 4, 2009, 11:40 AM
http://www.google.com/search?q=sighting+rifle+25+yds&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

This may help.

As for the farther ballistics, check the table and see what else is 0, you should be close, but your scopes mount may cause this to vary due to a different line of sight.

rhtwist
June 4, 2009, 11:49 AM
thanks again. Will begin my reading up.
rhtwist

Uncle Mike
June 4, 2009, 12:05 PM
Keep in mind that the 'ballistic charts' you may be using have had their data compiled relative to parameters set forth.

In other words, most charts use 24" barrels, if for instance your barrel is but only 16", you must subtract a set amount of velocity in Feet Per Second, if this is what the chart is figured in, from the base velocity to recalculate parameters for your barrel length.

Also sight height will affect the outcome of the 'ballistics'.

It might be to your best intrest to utilize one of the many free online ballistics calculators such as the one at or http://http://www.biggameinfo.com/BalCalc.aspx next, http://http://www.hornady.com/ballistics/ballistics_calculator.php
and http://http://www.realguns.com/index.htm.

These are some of the easier ballistic calculators to use.

Good Sighting- :D

Uncle Mike
June 4, 2009, 12:09 PM
Also try http://http://www.airgunhome.com/pages/calculators.html

You might like this one.

rhtwist
June 4, 2009, 12:39 PM
Hello Uncle Mike,
Thanks for the links. Have to do a little thinking and understanding first. Wish me luck.
rhtwist

Uncle Mike
June 4, 2009, 01:11 PM
You can do it.... no doubt!

Just 'plug in' the prompted data into the calculators and click the go button...

Remember the sight height is from the ' center line of the bore ' and not the top of the barrel. :rolleyes:

Vern Humphrey
June 4, 2009, 03:04 PM
How high are your sights above the centerline of the bore?

Plugging in 2" above height of bore, Oheler Ballistics Explorer gives a max ord of about 10.6" at 160 yards for az 300 yard zero. A lower height of sights would give an even higher max ord for a 300 yard zero.

rhtwist
June 4, 2009, 03:34 PM
Thanks for the responses. How is the ballistic coefficient determined, it seems to be required. I have a 3" sight centerline to bore centerline approx. also Vern Humphrey what is the "max ord". Sorry for inexperienced(politely) / dumb(regular) questions.
rhtwist

Vern Humphrey
June 4, 2009, 03:50 PM
How is the ballistic coefficient determined, it seems to be required.
Ballistic coefficient is determined by shooting over spaced chronographs and then calculating the BC by the amount of velocity lost between the first and second chronograph. Normally, this is done by the ammunition manufacturer. If you use Ballistic Explorer, you have an ammunition library with that program that will allow you to simply select various factory loads with known Ballistic Coefficients.

I have a 3" sight centerline to bore centerline approx.
That will give you a max ord of about 9.6" at about 161 yards.

also Vern Humphrey what is the "max ord".

Max Ord is the maximum height the bullet reaches. When used with small arms, it is measured from the line of sight. Another name for it is maximum height.

rhtwist
June 4, 2009, 11:08 PM
Thank You.
In your opinion is 300 yards a good zero or should I go less with the current setup. Thanks for your opinion and help.
rhtwist

Vern Humphrey
June 5, 2009, 10:56 AM
I can't answer that unless I know why you are zeroing?

If your intent is to shoot at 300 yards at targets, by all means, zero at 300 yards. If your intent is hunting or something similar, that high max ord will result in many misses at shorter ranges.

rhtwist
June 5, 2009, 11:04 AM
Hello Vern Humphrey,
An extremely valid question! I was just mind doodling on the general purpose of the firearm. Answered my question with a question. Neatly done. Thanks.
rhtwist

Vern Humphrey
June 5, 2009, 11:18 AM
For general purpose shooting, a good rule is to zero with a max ord of 3". In your case, this would be a zero of 200 yards. The bullet would be about 3" above the line of sight at about 122 yards, dead on at 200 yards, and 3" low at about 230 yards.

So 230 yards would be your Maximum Point Blank Range -- at all distances out to that range you could assume a hit within 3" of point of aim.

At 300 yards, point of impact would be about 13 1/2" low.

rhtwist
June 5, 2009, 11:30 AM
Thanks Sir,
What would the 25 yard setting be for the 200 yard range with the 3" height.
I do appreciate your help.
rhtwist

Vern Humphrey
June 5, 2009, 12:21 PM
About 0.8" low.

rhtwist
June 5, 2009, 01:03 PM
You da man! I like the the sound of that. Perfect thank you much again.
rhtwist

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