We all know from repeated KD training that a standard velocity .223 zeroed at 25M should be right on for about 300 yards. However, I just ordered and received a Nikon Carbine scope which has the holdovers out to 500 yards but which indicates that its zero is for 200 yards. I am thinking I need to be about 1MOA low at 25M to get this zero. Again, this is for standard velocity .223s using 55 gn. bullets. Does anyone think the 25M zero is different? Thanks!
The reason that we teach the 300yd far zero for .223 is because of the sight height above the line of bore on an ar15. This will change if the center line of the scope is lower or higher than standard ar15 sights. If the scope is lower your far-zero will be closer when your near zero is 25m. And remember this is a general rule, there are other factors like sight radius that effect the difference between far and near zero. The only way to know for sure is test it, or do the math. I'm a fan of practical application, (not a math geek).
CH
My scope is mounted on top of the carry handle. This makes my 25m zero the same at 500yds. You have to just go out and shoot it in. Be sure to write it down. Two Wolves
Here is a link to a decent ballistic calculator:
http://www.shooterscalculator.com/ (http://www.shooterscalculator.com/)
It will take the pertinent data, MV, Wt, Hight above bore, BC..... and come up with some pretty good comeups for your rifle/ammo combo.
2cl
Thanks Ron! That is a great resource.
As others have implied, and it needs emphasized, the final product is what the target results are at the actual distances. And for those conditions in which you shot.
This will be your real time come-up data. Make a chart and post it on your buttstock.
You may surprised at how the real time data results vary from the ballistics programs, standard come-ups charts, etc.
It can be frustrating.
But you need a starting place and this is how I start.
Quote from: Shooter30-06 on October 05, 2012, 10:55:16 AM
We all know from repeated KD training that a standard velocity .223 zeroed at 25M should be right on for about 300 yards. However, I just ordered and received a Nikon Carbine scope which has the holdovers out to 500 yards but which indicates that its zero is for 200 yards. I am thinking I need to be about 1MOA low at 25M to get this zero. Again, this is for standard velocity .223s using 55 gn. bullets. Does anyone think the 25M zero is different? Thanks!
Nikon has an online calculator for your scope. You have to realy go online and put in all the data and it will tell you a rough estimation of what the BDC rings are.
from several scope/ AR combinations I say:
2 1/4 moa low at 25 meters for a 200 yd zero
http://www.nikonhunting.com/page/spot_on
This program is fair to middlin.
Answer the questions, BUT be sure to measure and input the correct scope height (the default is 1.5") mine is 2.5"
You may be able to move your dials once to "Zero" the rifle. This will now make your 25 yard your baseline zero (something you can always return to.)
Then the world is your oyster.The more precise your #s the more dialable zeros you can have.
I'm good from 25 out to 300 with 55Gr and now trying to get to 600 with 77Gr.
The trajectory for an AR, starting from 100, is 2-2-3-4-5-6 (for 20" barrel and 55 or 62 grain ball). Zero it 2 MOA low at 25 and you will be real close. Fine tune at full distance if you have the opportunity.
In Matthew Bracken's "Domestic Enemies", he states that a 15 yard zero gives a 200 yard zero. It would be interesting to compare that zero with the POI at 25m.
dond
In my experience, for optics mounted in the same plane as the factory irons, a 50m zero equals a 200m zero. That's not just my experience either... that is a pretty commonly taught zero for carbine courses and whatnot.
If you think about the physics involved, if a 25m zero is a 300m zero, a 15m zero would have a second zero at an even farther distance, being that it would require the barrel to be aimed up even more to intersect POI at such a short distance.
A 200 yard zero is commonly referred to as battlefield zero. With proper sight height on an AR15 it works out to 50 and 200 (roughly). Puts you about 1 + 5/8" high at 100 assuming a 16" barrel with carbine gas system shooting 55fmj.
The good thing about battlefield zero is your point of aim (POA) will be close to your point of impact (POI) from 0 to 275. At 0y your POI will be 2" low of POA, at 25y a little less than 1" low, at 50y your POA intersects your POI. At 100 your POI will be roughly 1.578" above POA. At 200y POA again intersects POI. Around 275y your POI will be around 2" low of your POA.
This means that from 0-275y yours point of impact will be within 2" high or low of your point of aim. Hence the name battlefield zero. Most small arms combat happens within that distance. Making appleseed of utmost importance. Having longer arms in boxing is an advantage as well.
If you are familiar with Geometry/Trigonometry/Physics you can think of the POA as a straight line and the bullet as a trajectory or 1/2 parabolic curve. Using those types of equations is how soft/hard dope is estabilished and how ballistics calculators perform their job.
15 yard zero will end up very high at 100 and 200, field zero will be far past 300.
I am a fan of the Maximum Point Blank Range (MPBR) Zero.
No bothering with hold over or hold under from contact out to MPBR.
I didn't know what MPBR was until I did some research on it after reading it here. 50/200 is very close to MPBR with the 5.56x45 cartridge.
Just as an exercise in thought: Could you 25 meter zero it using the 2nd (300 meter?) dot to get an approximate 300 meter zer0?
Quote from: DEH on January 28, 2013, 08:25:49 PM
Just as an exercise in thought: Could you 25 meter zero it using the 2nd (300 meter?) dot to get an approximate 300 meter zer0?
They'd be one and the same or very close to it....O.L.
worked pretty well with the Vadala M2.
I use the RIBSZ for a 50 and 200 yd zero. http://www.ar15.com/forums/t_3_18/328143_RIBZ_____Revised_Improved_Battlesight_Zero__now_with_down_loadable_50_yard_zeroing_target_.html