Zeroing my new AR

[rogerjames]

So I've read the basics of zeroing and I'm relatively comfortable with the concepts and different options, ie 50/200, 100 etc.

I understand that the standard A2 rear site on most ARs is set for a zero from 300m-800m. So if one wants to set a 50/250 zero or 100 zero, than some elevation settings need to be changed on the rear sight so that POA will equal POI.

My Colt 6720 came with a flat top and pop up rear sight. The manual that came with rifle only discusses settings for the A2 carry handle type rear site, and the info I am familiar with online gives specific elevation changes for this same carry handle rear sight.

Is my flat top flip up rear site also configured from the factory for a 300-800m zero? I am interested in setting a 100 zero, but I am confused where to start and what changes to make.

 

[tuj]

start at 25, zero, move to 50, zero, move to 100, final zero.

easy as pie.

oh yeah, zeroing is related to your ammo, so don't mix brands or weights when zeroing.

 

[Arizona_Mike]

Everything you could possibly want to know and more: http://www.ar15.com/forums/t_3_18/328143_RIBZ_____Revised_Improved_Battlesight_Zero.html

Mike

 

[rogerjames]

Everything you could possibly want to know and more: http://www.ar15.com/forums/t_3_18/328143_RIBZ_____Revised_Improved_Battlesight_Zero.html



Mike

Thanks Mike, but I've read that already. All that info is based on an A2 carry handle rear sight. I am asking if my flat top flip up rear sight will require the same adjustments.

Should I assume that my adjustments are the same for the removable carry handle? It's quite possible that I am missing something obvious.

 

[ontarget]

When I was shooting the A2 for Uncle Sam, we used a 200 yard zero with the rear sight elevation set at a given value then adjusted the front sight pin to get it to the appropriate elevation. Then once we had the 200 yard zero we would make rear adjustments from there for 300/500 yards. On the A2 a 200 yard zero should put your POI in a human torso from 0 out to 300 yards with no sight adjustment.

 

[Warp]

It sounds like you have one of the newer Colts that came with a Magpul MBUS (or MBUS2) flip up (technically back-up I suppose) rear sight, and a PMAG.

That rear sight lacks some of the functionality of a fancy carry handle rear sight, but if you are only going to set one zero and leave it that doesn't matter.

Just do what tuj said. Start close, like 25 yards, so even if it's way off you should be on paper. Zero there. You may even zero it approximately an inch and a half low, or whatever it works out to be at 25, and then go to 100.

Don't forget that you can adjust elevation on the front sight if it helps to get you zero'd while having the rear sight where you want it (not close to maxed out in either direction or something funky)

With typical ammo like XM193 or XM855 a 50 meter [near] zero will come back on [far zero] at something like ~210, it isn't really 50/250. Most people will zero at either 50 or 100, I think, but some use 25 as you can still be on a torso type/size target to over 300 that way. More variance in between though.

Read:

http://www.m4carbine.net/showthread.php?65679-AR-15-Zeros-and-Trajectories

 

[4thPointOfContact]

From the same thread, this will always be my favored zero.

Never more than 5 inches high all way out to almost 200 yards and not more than 5 inches of drop almost all the way out to further than I contemplate engaging anyone short of an apockyklips.


There's nothing 'magical' about a 25, 37, 50 or 100 yard zero. You could measure 37 yards as 19.8 Smoots and the distance stays the same, only the nomenclature changes. Zero at 20 Smoots and you'll be good to go.

 

[4thPointOfContact]

double-tap

 

[rogerjames]

Thanks for all the responses but not sure I have my answer. Just to reiterate... I have read the RIBZ, Santos zeroing threads and I am familiar with their idiosyncrasies. I prefer the 100 zero for its flatter path and fewer calculations for distances shorter and after.

My question again is... The A2 carry handle rear sight is factory set for zeros from 300-800m. If using the RIBZ or Santos methods, the elevation of the rear sight must be adjusted so that POA will match POI. I am familiar with how to do that using the methods and measures described in those threads AND in my owners manual.

However... my rifle does NOT have a carry handle. It has a flat top with a flip up rear sight, so as far as I can discern, the measures and elevation recommendations described in those threads and in my manual are not specific for my set up. I am asking if anyone knows what the Colt factory zero is for a flat top with a pop up rear sight? And... If it is the traditional 300-800m zero, does anyone have a resource for the rear sight adjustment to bring POA equal to POI at 100 yards?

 

[303 hunter]

Flip up sight is the same height as carry handle sight.

 

[rogerjames]

Flip up sight is the same height as carry handle sight.

Well if that's true, then I know what to do from there

 

[Warp]

Flip up sight is the same height as carry handle sight.

That ^^

Go to the range. Shoot at 25 yards. Adjust windage/elevation of the sight to put the group where you want it (low at 25 obviously). Then move to 100 and zero it dead on there. That's it.

 

[gotigers]

I zero all of my ARs to the 200. Everything out to 250 yards is +/- 2". I hold center and know I will get a good hit. 300 is 8-10 inches holdover depending on load. too easy.

Most of the HP match shooters use 100 yard zero, but I know many many more 3 gunners that use 200. For fast shooting it is so easy. For HP matches when you have the time to dope up, 100 is probably for you.

 

[Captains1911]

You adjust the front sight when zeroing for elevation, not the rear, regardless of rear sight type.

 

[Arizona_Mike]

Thanks Mike, but I've read that already. All that info is based on an A2 carry handle rear sight. I am asking if my flat top flip up rear sight will require the same adjustments.

Should I assume that my adjustments are the same for the removable carry handle? It's quite possible that I am missing something obvious.

I'm really not sure what you are asking. The sight height of these flip-ups are the same as carry handle sights so the rise and drop vs. zero will be the same. Just zero your gun to 100 years like you would do with any other gun. I am not familiar with that exact sight but my guess is it is only windage adjustable in the rear (and elevation adjustable on your front post).

Edit: just found out on another web page that it is a Magpul rear sight so it is only windage adjustable.

Are you presuming that the gun comes zeroed to a particular range and you are looking for an adjustment for that range to 100 yards? Generally speaking guns, particularly low cost models ARE NOT factory zeroed.

Take it to the range. Boresight to 25 or 50 yd to get on paper and shoot at 100 to get your adjustments. Adjusting the front post is much easier with a tool like this: http://www.amazon.com/s/?ie=UTF8&ke...vptwo=&hvqmt=b&hvdev=c&ref=pd_sl_7x91dlh04h_b however you can use a bullet tip.

That said, unless your are shooting at exactly 100 yards for a reason, 100 yards is an all-around poor zero for 5.56mm.

Mike

 

[Warp]

....

That said, unless your are shooting at exactly 100 yards for a reason, [100] yards is a poor zero for 5.56mm.

Mike

100 yards is a fine zero for a 5.56 carbine, and there are some pretty big proponents of it. It may not be what you want, but there's nothing at all wrong with it.

Here is a decent discussion on the matter:

http://www.m4carbine.net/showthread.php?107572-Zen-of-the-100-Meter-Zero

 

[Arizona_Mike]

100 yards is a fine zero for a 5.56 carbine, and there are some pretty big proponents of it. It may not be what you want, but there's nothing at all wrong with it.

Here is a decent discussion on the matter:

http://www.m4carbine.net/showthread.php?107572-Zen-of-the-100-Meter-Zero

Interesting link and I am digesting it with an open mind. Thanks.

Mike

 

[REB]

I think you are confused by the fact when setting zero with the standard A2 rear sight you can depending on zero set the rear sight down a number of clicks to maintain the marking on the sight. The A2 sight is adjustable for elevation with markings from 300 to 600 meters.

Most backup flip rear sights are not adjustable for elevation, windage only. You have one zero with no further adjustment.

With either type the front sight is adjusted to set the zero. So with a backup sight you simply adjust the front sight elevation for the zero of your choosing.

 

[readyeddy]

REB got it. Your rear sight cannot adjust from 300-800m like the A2 carry handle sight.

With the carry handle sight, you can apply what you probably read about the improved battle sight zero and adjusting the rear sight to get a 200 yard zero. I did that for my fixed carry handle rear sight.

But with the back up flip up sights, you just have the one setting.

 

[rogerjames]

I think you are confused by the fact when setting zero with the standard A2 rear sight you can depending on zero set the rear sight down a number of clicks to maintain the marking on the sight. The A2 sight is adjustable for elevation with markings from 300 to 600 meters.



Most backup flip rear sights are not adjustable for elevation, windage only. You have one zero with no further adjustment.



With either type the front sight is adjusted to set the zero. So with a backup sight you simply adjust the front sight elevation for the zero of your choosing.

Thanks man, that's what I eventually figure out last night playing around with rifle. The standard A2 rear sight is set for a 300m zero. Any idea what the approximate zero is with factory FSB and flip up rear sight? If it also around the 300m mark, do you think there is enough adjustment in the FSB to achieve a POA = POI @ 100 yards?

 

[Captains1911]

There is no "factory zero." You can zero it for whatever distance you choose. The front sight post has plenty of adjustment range. You are overthinking it.

I have 2 ARs with folding rear sights (no elevation adjustments) and standard FSB. I have them both zeroed at 50 yards. If I wanted to I could also zero them at 25 yards, 100 yards, etc.

 

[David4516]

Odds are it is NOT factory zeroed. And even if it were, you'd want to re-zero it anyway with whatever ammo you plan on shooting. I think you're just going to have to go to the range and mess around with it, in order to get it where you want it.

If you are interested in a flip up sight that is adjustable for elevation, check this out:

http://www.amazon.com/MaTech-Mil-Spec-Back-up-Iron-Sight/dp/B002E6SXN4

I found one on ebay for $30 and I really like it.

Even with one of these, you'll want to zero for elevation using the front sight. So you might want a sight adjuster tool, like one of these:

http://www.amazon.com/Tapco-Intrafuse-Front-Sight-Tool/dp/B002E6T7AC

Hope this is helpful.

 

[David4516]

Also, there are several factors that will effect trajectory. The ammo is a big one, how heavy is the bullet? What is it's ballistic coefficient? Etc.

Barrel is another big one. The 20 inch rifle barrel will shoot flatter than the shorter carbine barrel.

Only way to know for sure what your particular rifle/ammo combo will do is to zero it as stated above, and then chronograph it and find out EXACTLY what velocity you're getting. Then plug it into a ballistics program. You can find some pretty good ones online for free, like this for example:

http://www.hornady.com/ballistics-resource/ballistics-calculator

In my own AR-15 for example, I shoot reloads with 55gr soft point bullets, with a BC of 0.235, at approx 2,800 feet per second velocity. I have it zeroed at 25 yards. I punch those numbers into the link above and it tells me that with a 25 yard zero I should also be dead on at about 200 yards. It will shoot a little high between 25 and 200, and anything beyond 200 will be lower and lower...

 

[rogerjames]

Thanks, much appreciated.

 

[David4516]

I should mention that my 25 yard zero is with the red dot sight I have, NOT the MaTech flip up sight with the elevation adjustments. I used the instructions that came with the MaTech to zero it, so that the elevation adjustments would be correct. (Set the sight to the white line, then zero at 25 meters using the front sight post to change elevation)

The thing is that these are calibrated for military ammo (62gr) so it will still be a little off if I'm shooting my reloads (55gr), but I think it will be at least in the ballpark. What I really need to do is test it out at various ranges and see what the real-world performance is. If the POI is too far off from the POA I might as well go back to a flip up sight that doesn't adjust for elevation (again I'm expecting a little variation but I want it to be at least somewhat close).

I haven't gotten around to testing it yet, partly because it's my backup sight and it's not been a big prioity for me (I know it works at short range and what are the odds that I'll shoot at 500 meters/yards with my backup sight anyway?), and partly because in my area, it's hard to find a place to shoot at that distance (too many trees/vegetation here in the northwest).