View Full Version : Iron zeroing advice
I’ve got a Kino, thanks to the EE. I went digging in my parts bin for a rear sight and found an old RRA A2, non-carry handle. I think LMT used to sell similar, or maybe they still do. I Z’d it at 25 yards and moved on with my life, because I didn’t originally plan on shooting it very far.
But the range wheel is too tempting. If I wanted to shoot it to like 500, how should I go about zeroing it? Its a Mid-length, A-frame FSB. It has a longer sight radius than a M4, but shorter than a M16, and a 12.5” barrel. The wheel is 6/3. I have 62 and 68/69gr ammo, at 5.56 speeds. I also have other stuff, but those are what I generally like.
Anybody ever do this, or do I just need to wing it and see what happens? I suspect the range wheel will have less effect than needed.
I shot you a text.
I zeroed a 6/3 carry handle on a 14.5" mid length with FSB by loosening the elevation screw in the carry handle, setting the wheel to be 2 clicks below the 6/3 mark, then retightening the screw. I zeroed it at 200y and was actually able to use the elevation adjustments out to 400y on steel without any significant problems.
I never shot it on paper past 200y, but I imagine that it wouldn't be difficult to take a paint pen and mark the wheel at the actual elevation adjustments for each range. From a practical standpoint, I didn't have a problem with the 14.5" middy when zeroed this way and never bothered to dig any deeper. It worked.
Ammo was 62g Magtech FMJ.
On a 6/3 carry handle you need to go 4 clicks past , and then zero at 50/200 with 14.5 or 16" bbl. No idea what a kino is.
No idea what a kino is.
They're 12.5" ARs with a midlength FSB. They usually have a carbine gas system with a low profile gas block and the FSB is just used as a sight and handguard attachment point. However, with 12.5" midlength barrels available, they could also be made that way.
*ETA: Here's a link to a Kino upper, as an example
https://bravocompanyusa.com/bcm-standard-12-5-carbine-upper-receiver-group-kino-configuration/
Zero it the way GTF425 or Uncas47 outline. At 25 yards your group should impact one inch below of point-of-aim. That should give you a 200-yard zero (250 for a 20-inch barrel).
Use the 69s -- they're a better quality bullet -- and dial to 500. You should hit a 500-yard Army E-type silhouette, maybe one or two clicks to fine-tune. 69s can go all the way to 600 in a 20-incher but will get blown around more than 77s if you have much wind.
Here's a drop card for you which should be close. This is for a 69 Sierra going 2550 FPS from an 8-twist barrel:
https://www.ar15.com/media/mediaFiles/18978/692600_jpg-2157021.JPG
Your post is quite timely. I just moved an LMT A2 non-carry handle to a lightweight (relatively) 16"er. If the wheel settings don't match up closely enough with actual POI, I will just count clicks for longer distances.
The RRA sight seems to be good quality. The clicks are a bit more distinct than the LMT, and it doesn't have the huge knob on the side. My RRA (that I bought while waiting for the LMT to become available) has been on a 16" 308 AR, but all I've done with it so far is a basic zero.
Pics aren't showing, but it is possible to get a 100 yard setting by bottoming the elevation out 6 clicks below 6/3.
https://www.m4carbine.net/showthread.php?65679-AR-15-Zeros-and-Trajectories
Hobby Lobby has Sharpie extra fine paint markers that work well for marking the added elevations on the wheel.
This article help me understand the concept >>> https://savannaharsenal.com/2017/04/08/how-to-zero-ar-15-a2-type-sights/
Thank you for the replies so far. I don’t think I phrased my original post well. I’m familiar with zeroing and using A2 iron sights on the M16 and the M4. What I did not know, is how this translates to a Kino when dialing for 400 or 500 meters. Because it has a non-standard sight radius and barrel length, and I’m using an aftermarket rear sight of unknown calibration.
Here’s why I thought it would be complicated: any given number of clicks of elevation adjustment on the rear sight of a 20” rifle equals a certain MOA. Turns out, thats probably roughly 0.5 MOA, since there are 24 clicks on the wheel between 300 and 600 meters, and to adjust between those ranges with M855 and a 20” barrel, you need about 12 MOA. So I would guess its design is intentional. However, with a carbine or mid length sight radius, the MOA per click changes, because, angles. More MOA per click with the shorter radius. It works out good enough for .gov work with the M4, because the shorter sight radius is matched with a lower velocity. It needs 14 MOA to go from 300 to 600 meters. ASSuming the elevation wheel is spot on for 600 meters (doubtful) it would need each click to be 0.58 MOA, which is believable. . So the monkey wrench is that the Kino has a midlength site radius, but a short barrel.
Here’s why it doesn’t matter: some bs napkin math leads me to believe that on a middy, a click on the range wheel might be somewhere in the neighborhood of .55 MOA. Yeah, I know. Its probably not that precise. To get from a 300m zero (NOT 25) to 500m, I need to come up around 8 MOA with either 62 or 68 gr ammo. 14 clicks takes me to the 500m setting on the wheel, which should give me somewhere near 7.7 MOA. So maybe like one more click. Or not.
My math may be way off, best way to find out is to shoot it. But it looks like I should be within a click or two of the indicated range on the wheel, as long as I true my zero at 300. I’ll revisit this thread in a month or three after I shoot it to 500 or 600. Based on the lack of internet discussion, I may be the only idiot that wants to dial dope on such a rifle.
My math may be way off, best way to find out is to shoot it. But it looks like I should be within a click or two of the indicated range on the wheel, as long as I true my zero at 300. I’ll revisit this thread in a month or three after I shoot it to 500 or 600. Based on the lack of internet discussion, I may be the only idiot that wants to dial dope on such a rifle.
You are definitely not an idiot and count me IN as awaiting / looking forward to your results sir. :)
Because it has a non-standard sight radius and barrel length, and I’m using an aftermarket rear sight of unknown calibration.
Can't you just count the threads to determine what it is calibrated at (if non-standard) or not going to be useful info for you as the sight radius is different???
... it has a non-standard sight radius and barrel length, and I’m using an aftermarket rear sight of unknown calibration.
... any given number of clicks of elevation adjustment on the rear sight of a 20” rifle equals a certain MOA.
... the monkey wrench is that the Kino has a midlength site radius, but a short barrel.
... best way to find out is to shoot it. But it looks like I should be within a click or two of the indicated range on the wheel, as long as I true my zero at 300. I’ll revisit this thread in a month or three after I shoot it to 500 or 600. Your logic follows well. The shorter sight radius means both elevation and windage clicks will carry more. These kind-of compensate for the velocity loss with a shorter barrel.
Shooters at the annual Army Championships at Benning use M4s, both with ACOGs and Matech irons. Bullets still hit E-types at 500, and that's with 14.5-inch standard carbine barrels. I can't nail a drop chart for you as I don't know many who routinely use a 12.5 to 500. :)
https://www.thefirearmblog.com/blog/wp-content/uploads/2019/03/1000w_q95.jpg
Your reasoning seems sound, but your numbers might be a bit off.
On a standard mil-spec detachable carry handle, the elevation screw moves the rear sight 0.075” per turn — but see caveat below! With the ~20” sight radius of an A4, that translates to 13.5” at 100 yards, or 12.9 MOA. (As you point out, that’s a decent match for the adjustment needed to go from 300 to 600m). Each of the 25 clicks per turn then corresponds to 0.52 MOA.
With a middy FSB, the sight radius will be around 16.5” rather than 20” and the angular motion will be proportionally larger: each click will be 0.625 MOA, and the full turn 15.6 MOA.
The caveat is that it isn’t clear what you have for a rear sight — you say RRA A2, but a mil-spec A2 sight would have an elevation index marked 8/3 rather than 6/3. And the threads are very coarse: each full turn is I believe 0.150” rather than 0.075”, so all the numbers above would be doubled. The rear sights on an A2 and an A4 may look similar from the outside, but inside they’re different!
To make things even more confusing, there are commercial sights out there with a pitch of 0.050”. In that case everything would move only 2/3 as much as with the standard 0.075”.
There may be other “match” options too, with even finer threads.
If you have a way to measure how much your rear sight moves with one turn of the elevation knob, that would be useful to know.
You may need to get a 25 or 50 yd zero and then walk it on out and record your dope as you go and tape it to the gun. It's empirical data that way whatever the sight radius, or thread pitch, or ammo. You need to shoot any calculation anyway to verify.
Can't you just count the threads to determine what it is calibrated at (if non-standard) or not going to be useful info for you as the sight radius is different??? I’m going to measure how much a turn raises it and provide to Curlew below, as he seems more Trig savvy than me.
Your logic follows well. The shorter sight radius means both elevation and windage clicks will carry more. These kind-of compensate for the velocity loss with a shorter barrel.
Shooters at the annual Army Championships at Benning use M4s, both with ACOGs and Matech irons. Bullets still hit E-types at 500, and that's with 14.5-inch standard carbine barrels. I can't nail a drop chart for you as I don't know many who routinely use a 12.5 to 500. :)
My 12.3” is fast and launches Hornady 68s at 2722 fps at I think 90*. If I back that down to 2690 (I haven’t chronoed this barrel yet), that makes me a minute flatter at 500 than what you posted earlier.
Like you, I use Litz BCs and I usually use Strelok or Ballistic AE to figure out the best strategy for zeroing a LPVO with BDC, like the T5Xi. The math usually works out to get me first round hits on F-types to 500 yards.
Your reasoning seems sound, but your numbers might be a bit off.
On a standard mil-spec detachable carry handle, the elevation screw moves the rear sight 0.075” per turn — but see caveat below! With the ~20” sight radius of an A4, that translates to 13.5” at 100 yards, or 12.9 MOA. (As you point out, that’s a decent match for the adjustment needed to go from 300 to 600m). Each of the 25 clicks per turn then corresponds to 0.52 MOA.
With a middy FSB, the sight radius will be around 16.5” rather than 20” and the angular motion will be proportionally larger: each click will be 0.625 MOA, and the full turn 15.6 MOA.
The caveat is that it isn’t clear what you have for a rear sight — you say RRA A2, but a mil-spec A2 sight would have an elevation index marked 8/3 rather than 6/3. And the threads are very coarse: each full turn is I believe 0.150” rather than 0.075”, so all the numbers above would be doubled. The rear sights on an A2 and an A4 may look similar from the outside, but inside they’re different!
To make things even more confusing, there are commercial sights out there with a pitch of 0.050”. In that case everything would move only 2/3 as much as with the standard 0.075”.
There may be other “match” options too, with even finer threads.
If you have a way to measure how much your rear sight moves with one turn of the elevation knob, that would be useful to know. measured at the rear, I got 0.0755” for one turn. Measured at the front, I got 0.0775”.
You may need to get a 25 or 50 yd zero and then walk it on out and record your dope as you go and tape it to the gun. It's empirical data that way whatever the sight radius, or thread pitch, or ammo. You need to shoot any calculation anyway to verify.
Yeah, I think thats what I’ll have to do.
measured at the rear, I got 0.0755” for one turn. Measured at the front, I got 0.0775”.So I’m unclear on front vs back (of what?), but let’s call it 0.075”, which is the number I’ve always seen for a detachable carry handle. Measure the distance from the rear aperture to the front post; it should be something like 16.5” if I’ve correctly understood what you’ve got there. Then if you’re shooting at 100 yards, or 3600”, one turn of the elevation knob moves the point of impact by
0.075” x (3600” / 16.5”) = 16.4”
If you like working in MOA, that’s about 15.3 MOA per turn, or 0.625 MOA per click.
It sounds like you’ve already got a handle on the trajectory side of the problem and can figure how much extra elevation angle you need to go from your zero distance out to 500 yards or meters. Convert that into clicks, at 5/8 MOA per click, and I bet you’ll at least be on paper!
So I’m unclear on front vs back (of what?), but let’s call it 0.075”, which is the number I’ve always seen for a detachable carry handle. Measure the distance from the rear aperture to the front post; it should be something like 16.5” if I’ve correctly understood what you’ve got there. Then if you’re shooting at 100 yards, or 3600”, one turn of the elevation knob moves the point of impact by
0.075” x (3600” / 16.5”) = 16.4”
If you like working in MOA, that’s about 15.3 MOA per turn, or 0.625 MOA per click.
It sounds like you’ve already got a handle on the trajectory side of the problem and can figure how much extra elevation angle you need to go from your zero distance out to 500 yards or meters. Convert that into clicks, at 5/8 MOA per click, and I bet you’ll at least be on paper!
I measured from the flat bottom of the “Rear Sight Base” (part 15 in this schematic, which is not of my specific sight https://www.brownells.com/schematics/colt-/ar-15-rear-sight-assembly-sid808.aspx) to the ledge it sits on.
Sight radius is exactly 16.5”.
So, coming from a true 300 yard zero with 68 grain Hornadys I need 3.6, 8, and 13.4 minutes of elevation for 400, 500, and 600 yards. .625 minute clicks would give me 3.75, 8.75, and 15 MOA. That would absolutely get me on paper. If I do everything in meters, zeroing at 300m, then shooting at 400m, 500m, 600m, it actually gets even closer. Like, nearly exact, as if the sight is made for this combo.
Hornady 62 FMJ would need (using Hornady’s BC) 3.7, 8.3, and 14.2 MOA for 400, 500, 600 yards, so it might get pretty close, also. Its what I usually use at closer ranges, so that’s cool.
That 300 yard zero with Hornady 68s would be .21” low at 25, or be POI/POA at 27.5 yards, according to Ballistic AE. With Hornady 62 FMJs, it would be .32” low at 25 yards, or 29 yards near zero.
Thanks everyone! I think we’ve got the math figured out; I just have to shoot it.
So, I shot this thing some more. Kind of a frustrating day, with snow everywhere and awful wind. Ammo used was reloaded 556 62gr Hornady FMJ. Shot 1.5” low at 20-25 yards. 3 rounds all touching on a Shoot N See sticker. Decided not to adjust anything and go straight to 300, prone supported. Shot a foot right and 18” low. I adjusted the sights, and by some miracle, my next group was pretty close to the center of the target. Which had flipped upward in the wind, because I used tape instead of staples, and then refused to fall down. So I just shot the back of it. It was a 8”-9” group, off a little to the left, but too close to try to adjust any.
It was all downhill from there. I ran out of time to shoot at paper. I dialed the elevation wheel and took a few quick shots at the steel F-Types (Fast Freddy) at 400 and 480, but got no hits, and my buddy wasn’t able to spot my misses with his LPVO due to shit conditions. I could reliably pop the 8” steel at 200 and the F Types at 300, though.
I’ll have to revisit this later with paper at 400 and 500. Side note, I was able to zero a stock AK at 25 with the same luck for nailing my first adjustment. I was able to mostly repeatably hit the F Type at 300 with it, and get some hits at 400, using the graduations on the rear sight. Using Wolf 124gr FMJ. Might has well have been throwing rocks at the 480yd F-Type, though. 0/20 on that one.
More to follow later. Much fun was had.
Edit: misread my note on group size, so I fixed that. It was eyeballed, BTW.
It's snowing in South Carolina?!
Nah, I was in North Carolina for the weekend.
Edit for update: 12.5” BCM Kino/TurboK
XM855, 81*F
2825 fps
69 es
20.3 sd
I’ll have to revisit this later with paper at 400 and 500. Side note, I was able to zero a stock AK at 25 with the same luck for nailing my first adjustment. I was able to mostly repeatably hit the F Type at 300 with it, and get some hits at 400, using the graduations on the rear sight. Using Wolf 124gr FMJ. Might has well have been throwing rocks at the 480yd F-Type, though. 0/20 on that one. My son did research on AK battle sight zero. He asked me, "Did you know the AK's battle sight zero is 400 Meters?"
I had no idea.
I've shot a number of Uncle Sam's AKs but never delved into it deep enough to know that.
Youtube has a vid showing Russian paratroop trainees qualifying with AK74s at 100 or 200 Meters.
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