Whats your Red Dot Zero? 25-50-100 yrds?

**Pappabear** · 01-20-10, 18:24

Originally Posted by decodeddiesel

While I agree whole heartily that 50 yards is the ideal zero if your red dot sight is your primary optic, I do not think this is the answer for the OP.

My understanding from his post is that he is running an ACOG with a backup RDS, such as this:

In which case the height over bore of the optic dictates that all of the graphs presented in this thread are not applicable to his set-up.

I still stand by my original post that he should zero his RDS at 25 meters (or less) and even then he is going to have to become very familiar with the hold over and chin weld required to use an optic like this.

This is for the simple fact that his RDS is not his primary optic, it is an "Oh Shit - BOOM!" optic designed for engaging targets at extremely close CQB ranges.

That being said thanks to Derek and Molon for the graphs. They are very insightful and I have already used them to convert a few Army 25m zero die-hards here at my work.

Deco, how does this change? I run this set-up on one of my rifles and have the red dot on for 25yards, and the cross hairs at 100 yards. I wanted to change the red dot for 50, for flatter shots regardless-out to 200 yards. I know the scope is intended for long shots and RDS for CQB, however, if a target (enemy or yote) is running at 100 yards, I may prefer the RDS for better periphery vision and quicker acquisition.

Isnt 50 yards the best deal there? I see the RDS on top as more than just CQB, I see it as FAST!

How does distance with "Sight over bore" effect zero. Zero is zero

I'm a little cornfused.

pb

**JSantoro** · 01-20-10, 19:41

If you're using an ACOG, and have it zeroed @ 100yds, your bullet drop compensator is not tuned correctly, because that optic is scaled in meters. No net effect in most instances shooting at a human-torso-sized target from, say, 0-200m or so, but your shots beyond that will strike well below what you think, and the human trend is to blame the reticle, when it's the fault of the shooter that can't/won't RTFM.

100m is 109yds, if that helps; some folks don't grok metric. 27' of difference, practically meaningless on the front end of the arc, but a significant impact on the far end of it, presuming you want your BDC to be on.

Generally, the 50yd zero works VERY well for optics that set around 2.5" or so over center of bore. Higher than that (as in the above configuration), and the elevation angle of the barrel required to hit that 50yd mark is different from what it would be if you were using a standard irons/RDS sight height. You'll still have a no-shit 50yd zero, you'll just need to shoot to see where it recrosses you LOS on the downward end. It'll probably be further than the 225-255yd mark usually achieved, and the greatest height of the round over LOS ought to be greater.

Your ACOG will be somewhere around 2.755", model dependent, so whatever RDS you have on top will be at least an inch higher. Inside 50yds, it means you'll have a larger sight to bore relationship to remember, too. So, height over bore doesn't affect your initial zero, as that's something YOU establish, but if you punch it in to one of the ballsitic calculators, it'll give you a reasonable read on where it will hit on the far end.

**jp0319** · 01-21-10, 21:35

After reading "most" of the thread no one has mentioned green eyes black rifles. Kyle Lamb breaks down trajectory at different zero ranges, how high and low the shots fall with each out past 300, and also breaks it down by load 55gr and 62gr. Might be something to read if you hevent. I got more out of that section of the book than any other.

**Pappabear** · 01-21-10, 23:28

Originally Posted by jp0319

After reading "most" of the thread no one has mentioned green eyes black rifles. Kyle Lamb breaks down trajectory at different zero ranges, how high and low the shots fall with each out past 300, and also breaks it down by load 55gr and 62gr. Might be something to read if you hevent. I got more out of that section of the book than any other.

Cool, I'll check it out. Thanks

**Surf** · 01-22-10, 01:02

Originally Posted by Pappabear

Deco, how does this change? I run this set-up on one of my rifles and have the red dot on for 25yards, and the cross hairs at 100 yards. I wanted to change the red dot for 50, for flatter shots regardless-out to 200 yards. I know the scope is intended for long shots and RDS for CQB, however, if a target (enemy or yote) is running at 100 yards, I may prefer the RDS for better periphery vision and quicker acquisition.

Isnt 50 yards the best deal there? I see the RDS on top as more than just CQB, I see it as FAST!

How does distance with "Sight over bore" effect zero. Zero is zero

I'm a little cornfused.

pb

Trijicon manual suggests that the Dr Optic be zeroed at 40m, so 50 yards is in the ball park. Mine is set at 50yds. However I really do not like using the red dot mounted on top of the ACOG. I don't even have a chin weld, much less a cheek weld and being what I consider FAST and finding the dot in a down and dirty situation is not going to happen. I am much quicker just using the ACOG itself over the dot in a quick "oh shit" situation, even up close.

Also, the height offset really starts getting problematic with holds out to distance the closer in you zero it. If you attempt to zero it real close 15 yards or less, just look where the impact is when you move forward or backward just a yard or so.

**decodeddiesel** · 01-22-10, 09:26

Originally Posted by Pappabear

Deco, how does this change? I run this set-up on one of my rifles and have the red dot on for 25yards, and the cross hairs at 100 yards. I wanted to change the red dot for 50, for flatter shots regardless-out to 200 yards. I know the scope is intended for long shots and RDS for CQB, however, if a target (enemy or yote) is running at 100 yards, I may prefer the RDS for better periphery vision and quicker acquisition.

Isnt 50 yards the best deal there? I see the RDS on top as more than just CQB, I see it as FAST!

How does distance with "Sight over bore" effect zero. Zero is zero

I'm a little cornfused.

pb

Yes you're absolutely right, zero is zero. However if your POA crosses your POI line sooner (ie a closer zero) you can alleviate some of the excessive hold over you would need to compensate for the outrageous height over bore you have with an ACOG with a red dot on top.

My personal experience using the ACOG in combat is that I tend to drop into the main optic no matter what though. This can be somewhat corrected with training, but honestly I think anything say more than 15 meters out you're probably just going to drop into the ACOG anyway.

**Pappabear** · 01-22-10, 09:47

Also, the height offset really starts getting problematic with holds out to distance the closer in you zero it. If you attempt to zero it real close 15 yards or less, just look where the impact is when you move forward or backward just a yard or so.[/QUOTE]

Thank you, that helps. I am going to zero at 50 yeards with my doctor, just as my Aimpoints. Then I am going to see what a 10 / 20 / yard shot POI is on my Doctor vs. my Aimpoints. And see what impact that has on my guns, with my ammo, and with me at the wheel. I really want to be consistant with my need for holdover, POI etc with all my Red dots. My ACOG can differ a little at 100.