AR 100 yard zero question...

[Tackleberry]

Has anyone figured out the come-ups on an AR15 having a 100 yard zero using the rear-A2 sight? I have looked at the other threads and have found no answers to this particular question.

[EEL]

You have to ck with your ammo...but if you set your rear sight on 8/3 PLUS 1 click up, then adjust your front sight elevation for a 25 meter zero, that should put you in the ball park.  At Osage I found for 100 & 200 yrds, I was 8/3 MINUS 1 click.  300 yrds I was right on 8/3.  400 yrds too windy for those teeny weeny 55 grain bullets    I was using Wolf black box, A2 sight, 20" barrel.

If you have a 100 yrd zero, you will probably be 1 1/2" to 2" low at 25 meters.

EEL

[Tackleberry]

You have to ck with your ammo...but if you set your rear sight on 8/3 PLUS 1 click up, then adjust your front sight elevation for a 25 meter zero, that should put you in the ball park.  At Osage I found for 100 & 200 yrds, I was 8/3 MINUS 1 click.  300 yrds I was right on 8/3.  400 yrds too windy for those teeny weeny 55 grain bullets    I was using Wolf black box, A2 sight, 20" barrel.

If you have a 100 yrd zero, you will probably be 1 1/2" to 2" low at 25 meters.

EEL

I have several AR's zeroed with the 25 meter target. This particular zero is not good for shooting varmints around my farm, which is why I zeroed two AR's at 100 yards. I would like to be able to get in the ballpark with these two AR's should they be needed for longer ranges. I guess I will have to go out on a clear day and test it out, outback. Thanks.

[Old Dog]

That is the only way to be sure.  Most folks here ain't taking about a zero that allow you to hit a varmint sized target at 300 to 400 yds. away.  They're talking about targets of 16" or slighly bigger.

Even then, I'll bet if you take all your rifles out, shoot them with the same ammo at the same range (sight them in dead on at 300 yds, say, and then without changing ammo or adjusting the sights shoot them at 100, 200 and 400 yds. and they will not all hit the same point of aim. 

Every rifle is a little bit different from the next one.  One of the things that makes'em interesting.  Sometimes you run into a rifle that just seems to "break" the rules.  When you do, keep it, they are few and far between.

[EEL]

I think the moral of this discussion is this:  Where your rifle is zeroed doesn't matter to anyone except you.  What type / brand / bullet wt / powder / etc doesn't matter to anyone except you.  The books, ballistic charts, these boards, etc get you close enough to fine tune YOUR rifle.

What matters is that YOU know what range your rifle is zeroed at and what you need to do to your sights to hit a target at whatever range it happens to be at.  The ONLY way to do that is to actually do it!!!  Then write it down somewhere so you can retrieve it at that crucial moment. (as in tape it to your stock)

It would look something like this:

Lake City 55 gr
25m  8/3 +1  w 2 right    (this would be from "0" windage)
100   8/3 -1  w 2 right
200   8/3 -1  w 2 right
300   8/3      w +4 right  (total of 6 off zero)
400   4         w +2 right  (total of 8 off zero)

With this card, you could pick up your rifle and, even if someone monkeyed with your sight adjustments (as in demo'd how to change sights) reset it to 8/3+1, come off zero windage 2 clicks right.....and, for 25m using your LC ammo, you're there!!!!

If you change ammo, make a new card.  Save the old one in case you get more LC, you have a starting point to see if it is same same.

You never know what brand of ammo you may "pick up" (literally) so make a card for several different brands and bullet wts. if you can.

[Tackleberry]

I think the moral of this discussion is this:  Where your rifle is zeroed doesn't matter to anyone except you.  What type / brand / bullet wt / powder / etc doesn't matter to anyone except you.  The books, ballistic charts, these boards, etc get you close enough to fine tune YOUR rifle.

What matters is that YOU know what range your rifle is zeroed at and what you need to do to your sights to hit a target at whatever range it happens to be at.  The ONLY way to do that is to actually do it!!!  Then write it down somewhere so you can retrieve it at that crucial moment. (as in tape it to your stock)

It would look something like this:

Lake City 55 gr
25m  8/3 +1  w 2 right    (this would be from "0" windage)
100   8/3 -1  w 2 right
200   8/3 -1  w 2 right
300   8/3      w +4 right  (total of 6 off zero)
400   4         w +2 right  (total of 8 off zero)

With this card, you could pick up your rifle and, even if someone monkeyed with your sight adjustments (as in demo'd how to change sights) reset it to 8/3+1, come off zero windage 2 clicks right.....and, for 25m using your LC ammo, you're there!!!!

If you change ammo, make a new card.  Save the old one in case you get more LC, you have a starting point to see if it is same same.

You never know what brand of ammo you may "pick up" (literally) so make a card for several different brands and bullet wts. if you can.

That is the plan (to write down the comeups); rather than just rely on something taped to m yrifle, I plan to use finger nail polish to mark the ranges on the dial. It does matter to more than me though, for the same reason the A2 sites are calibrated at 300 meters with a 25 meter zero. Every rifle may be different, but a basic standard to start from is better that starting from scratch.

Just wanted to know if someone had the basic come ups for general use, similar to the 3-3-4-4-5 for .30 cal rifles. When I get the chance, I will get to it and let everyone know the results.

[MTGlass]

These ought to muddy the waters a bit...

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

http://www.ar15.com/forums/topic.html?b=3&f=18&t=328143