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Posted: 6/14/2024 4:57:00 PM EDT
[#1]
https://www.ar15.com/forums/ar-15/RIBZ--Revised-Improved-Battlesight-Zero/18-328143/
Sorry, I don't know how to make it hot. The method in the link above will allow you to modify your rear sight so that you can have your 50 yard zero and still use the elevation wheel to dial the listed distances. |
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Posted: 6/14/2024 6:03:24 PM EDT
[#2]
Quoted: I still enjoy shooting my 30+ year old first AR on occasion, a Pre-ban Colt Sporter (Lightweight) with carry-handle A2 sights. If nothing else it sure helps me appreciate optics on my other rifles. I’ve found that the 50 yard zero is likely the most appropriate for me and my older eyes so I set the distance “wheel” at 8/3 for 300 yards and zero’ed the rifle at 50 yards using the small aperture. A couple of questions: (1) By using the small aperture to zero at 50 yards is the large aperture also zero’ed for 50 yards? Is there any time I would use the larger aperture over the smaller one? (2) I assume that the 50 yard zero makes the additional settings on the distance “wheel” drastically incorrect and rather than use the wheel for distances past about 250 yards I would instead need to use holdovers at various distances? Thanks in advance for help! One of the dumbest ever ideas of .mil was the adjustable rear sight on a 300 yard combat weapon. Just set it and forget it, Tennessee elevation! Does your rear sight aperture(s) have any letters or numbers on it? When we Q'd with the M-16 the drill was, "hold low on the close sil's and high on the far ones and don't touch that F'n wheel". |
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Posted: 6/14/2024 7:11:53 PM EDT
[#3]
If you zero it properly at 25m the wheel will be correct with M855. Army doctrine for the A2 is zeroing at 25 meters, which will give you a basic 300 yard zero. You set the rear sight with the small aperture at 8/3+1 and zero on the 25m target. Once you zero at 25m, you move the sight down one click to the 8/3 setting and you are done.
The large aperture which is marked 0-2, is technically to be used for close engagements to 200 yards. |
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Posted: 6/14/2024 7:47:40 PM EDT
[#4]
Quote HistoryQuoted: If you zero it properly at 25m the wheel will be correct with M855. Army doctrine for the A2 is zeroing at 25 meters, which will give you a basic 300 yard zero. You set the rear sight with the small aperture at 8/3+1 and zero on the 25m target. Once you zero at 25m, you move the sight down one click to the 8/3 setting and you are done. The large aperture which is marked 0-2, is technically to be used for close engagements to 200 yards. The thing to reinforce is there is that sight adjustment that has to take place for the 25 meter zero and the A2. Prior to the "wheel" we zero'd about an inch low @ 25 meters, there was a special target for this. If you truly ZERO @ 25 meters you will be waaay high @ 300, and some guys forget about the sight adjustment. The actual .mil ZERO in essence is what we often now call a 36/300 zero. |
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Posted: 6/14/2024 9:42:36 PM EDT
[#5]
Quote HistoryQuoted: The thing to reinforce is there is that sight adjustment that has to take place for the 25 meter zero and the A2. Prior to the "wheel" we zero'd about an inch low @ 25 meters, there was a special target for this. If you truly ZERO @ 25 meters you will be waaay high @ 300, and some guys forget about the sight adjustment. The actual .mil ZERO in essence is what we often now call a 36/300 zero. The OP has an AR-15A2, so I'm kinda missing why you are bringing in A1 rifles to the discussion? The sights, ammunition and ballistics are different. I'm not really telling him to obtain a true 25M zero, I'm telling him to zero at 25M with the procedure I posted. 36M zero is just the Marine way of zeroing and it does the same thing as the Army way of zeroing at 25M without having to adjust the rear elevation drum to 8/3+1, and then moving it back down to 8/3 after obtaining a zero. The only bad thing I ever heard about a 300M zero is that you are shooting high from 100 - 200 + meters. We just aimed slightly low at the intermediate targets.  |
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Posted: 6/14/2024 11:15:53 PM EDT
[#6]
A 50/200 yd zero is a flatter trajectory than a 25/300 zero. The rise over point of aim is about half that of the 25/300 zero.
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Posted: 6/15/2024 12:39:30 AM EDT
[#7]
Quote HistoryQuoted: A 50/200 yd zero is a flatter trajectory than a 25/300 zero. The rise over point of aim is about half that of the 25/300 zero. There is no such thing as a 25/300 zero, at least with this platform. |
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Posted: 6/15/2024 1:06:25 AM EDT
[#8]
The OP has an AR-15A2, so I'm kinda missing why you are bringing in A1 rifles to the discussion? The sights, ammunition and ballistics are different. The relevant point is, the sights work the same. Prior to the adjustable rear sight we zero'd an inch low @ 25 to get our 300 meter dial-in. Upon the advent of the adjustable rear sight, you make a sight adjustment before and after, which accomplishes the same thing. The confusion comes when folks recall zero'ing at 25 yards but forget about the sight adjustments. |
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Posted: 6/15/2024 3:00:47 AM EDT
[#9]
OP, what do you have available for ranges distance-wise?
If you have an A2 sighting system, you may as well zero it properly so the BDC/elevation wheel is relatively calibrated. Just use the Army or Marine Corps procedure, as it will be “good” enough a for the purpose you describe. The USMC used 8/3 minus two clicks for a 200 YARD zero on a KD range. That will be close enough for your purposes to zero at 50yd and be +/- a click on the BDC. The USMC exploited the capabilities of the M16A2 compared to the Army. I, personally, would use the USMC zeroing method based on my experience with that system and as a Primary Marksmanship Instructor back in the day. Note, when you zero on the “near zero”, I.e. 25m/36yd, you are only approximating the zero distance for the at-range distance. It is important to zero at actual distance. If you zero the rifle at 50 yards, you will have a 50 yard zero. Ideally, you would confirm zero at 300m on the 8/3 setting, then drop two clicks for your 0-200yd/m battle sight zero. |
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Posted: 6/15/2024 7:57:36 AM EDT
[#10]
Considering he may be an older gentleman and guessing enjoying his rifle from the bench, it may be easier for him to put his sight at 8/3, zero at 50 on the small and enjoy it. If he wants to piddle, change the aperture and shoot 25/50/100 and make a note on the change if it matters to him.
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Posted: 6/15/2024 9:14:26 AM EDT
[#11]
Quote HistoryQuoted: There is no such thing as a 25/300 zero, at least with this platform. Quote HistoryQuoted: Quoted: A 50/200 yd zero is a flatter trajectory than a 25/300 zero. The rise over point of aim is about half that of the 25/300 zero. There is no such thing as a 25/300 zero, at least with this platform. Yes there is. With an optic I can zero at 50 and be within 7/8" at 200 |
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Posted: 6/15/2024 12:03:20 PM EDT
[#12]
Quote HistoryQuoted: Yes there is. With an optic I can zero at 50 and be within 7/8" at 200 If you zero an AR @ 25 yards you will not be near the target @ 300 due to the sight height.  Now if we move that same near zero to 36 yards, we hit @ 300  And to achieve that 36/300 zero with a 25 yard target we need to print about 3/4" or so below the center, depending on ammo, or adjust the "wheel" if you have one.  If I'm OP I just bottom out the rear and zero @ 50 and have fun. Everything out to about 225 will be point and shoot. If he wants to play with elevation beyond that either hold over or spin the wheel. |
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Posted: 6/18/2024 2:26:14 AM EDT
[#13]
Quote HistoryQuoted: There is no such thing as a 25/300 zero, at least with this platform.  |
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Posted: 6/18/2024 11:13:53 AM EDT
[#14]
Quote HistoryQuoted: there is with an iron sighted M4 https://uploads.tapatalk-cdn.com/20210215/b30ac4a09935366b5bdb90a5da431713.jpg Still doesn't compute: 
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Posted: 6/18/2024 12:09:06 PM EDT
[#15]
Quote Historyset your chart interval to 25 yds and zero to 300. you should be 0.5" low at 25. that's why close in pre-zeros should not be relied on. that half inch at 25 means means you're 5.5" off at 300 |
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Posted: 6/18/2024 1:29:28 PM EDT
[#16]
Quote HistoryQuoted: set your chart interval to 25 yds and zero to 300. you should be 0.5" low at 25. that's why close in pre-zeros should not be relied on. that half inch at 25 means means you're 5.5" off at 300 Right! As I pointed out above in this thread. There is no 25/300 zero. It is a 36/300 zero that we can achieve at 25 yards by zeroing low or making an adjustment to the rear. This is the original M-16 zero target, X shows where your group should be printing when the front sight is tucked into the "notch":  When the Uncle Sam went to the adjustable rear sight on the A2 and current, an adjustment is made to the rear when zeroing which accomplishes the same thing. Regardless of how we get there, we need to be printing low @ 25 to attain a 300 yard zero. How low depends on the ammo and barrel length, velocity. |
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Posted: 6/18/2024 2:21:52 PM EDT
[#17]
Quote HistoryQuoted: Right! As I pointed out above in this thread. There is no 25/300 zero. It is a 36/300 zero that we can achieve at 25 yards by zeroing low or making an adjustment to the rear. This is the original M-16 zero target, X shows where your group should be printing when the front sight is tucked into the "notch": https://i.imgur.com/lxxgURq.jpg When the Uncle Sam went to the adjustable rear sight on the A2 and current, an adjustment is made to the rear when zeroing which accomplishes the same thing. Regardless of how we get there, we need to be printing low @ 25 to attain a 300 yard zero. How low depends on the ammo and barrel length, velocity. Bottom line, the closer distance pre-zero doesn't matter once the proper long range distance is achieved. The 25/36/50 "zero" is just to get you in the ballpark until you can confirm at distance. Even plugging the numbers into a ballistic calculator and seeing where you should be at 100 (x.xx" high, etc) goes a long way. I zero my AUG to be 3.25" high at 100 which gives a 250m/275yd zero |
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Posted: 6/18/2024 5:30:29 PM EDT
[#18]
Snidely,
Per Army doctrine, you would use the larger aperture for close distances, 0-200m (hence the 0-2 marking thereon), and during low light conditions. Any other time, use the smaller aperture. |
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Posted: 6/18/2024 7:08:38 PM EDT
[#19]
Quote HistoryQuoted: I think we're both saying the same thing. Bottom line, the closer distance pre-zero doesn't matter once the proper long range distance is achieved. The 25/36/50 "zero" is just to get you in the ballpark until you can confirm at distance. Even plugging the numbers into a ballistic calculator and seeing where you should be at 100 (x.xx" high, etc) goes a long way. I zero my AUG to be 3.25" high at 100 which gives a 250m/275yd zero We are, that. I still see vets saying a 25 zero begets a 300 zero, but they are forgetting about the adjustment to the sight along the way. If all I have is 25 yards to zero, I zero 3/4" low @ 25 for a 300 yard zero regardless of ammo and then check downrange when I get the chance. Usually am within the margin of shooter error, or close enough for gov't work  For a 50/200 zero I start @ 1-1/4" low @ 25 and then confirm @ 200 |
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Posted: 6/28/2024 1:33:51 AM EDT
[#20]
Quote HistoryQuoted: There is no such thing as a 25/300 zero, at least with this platform. Technically, there is. As mentioned before, there was a special target placed at 25 meters that you had to zero about an inch low. This gave you a 36/300 zero, but you zeroed it at 25m. Hence the "25/300." It sounds weird after, but not making it up. |
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Posted: 6/28/2024 4:48:51 AM EDT
[#21]
Quote HistoryQuoted: Technically, there is. As mentioned before, there was a special target placed at 25 meters that you had to zero about an inch low. This gave you a 36/300 zero, but you zeroed it at 25m. Hence the "25/300." It sounds weird after, but not making it up. I believe that was the A1 target. You aim at center mass, but there was a circle where you want impact. Basically, it was a 50M zero back in the 70's. |
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Posted: 6/28/2024 9:04:36 AM EDT
[#22]
Quote HistoryQuoted: I believe that was the A1 target. You aim at center mass, but there was a circle where you want impact. Basically, it was a 50M zero back in the 70's.  The A1 target for normal sights was for a 250m zero. You zero'd at 25m on the L aperture then flipped back to the normal one 
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Posted: 6/28/2024 10:41:27 AM EDT
[#23]
Quote HistoryQuoted: Technically, there is. As mentioned before, there was a special target placed at 25 meters that you had to zero about an inch low. This gave you a 36/300 zero, but you zeroed it at 25m. Hence the "25/300." It sounds weird after, but not making it up. Well, no, "technically" there isn't. Zero indicates POI, and the near POI for a 300 yard/meter zero is 36 yards/meters. Mil likes to "sight in" @ 25, so mil "zero's" about an inch low @ 25 to achieve that 36/300 Splitting hairs and picking nits and all that
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Posted: 6/28/2024 2:08:48 PM EDT
[#24]
Quote HistoryQuoted: Well, no, "technically" there isn't. Zero indicates POI, and the near POI for a 300 yard/meter zero is 36 yards/meters. Mil likes to "sight in" @ 25, so mil "zero's" about an inch low @ 25 to achieve that 36/300 Splitting hairs and picking nits and all that |
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Posted: 6/29/2024 5:23:40 AM EDT
[#25]
If you zero at 25 METERS with M855 using an M4 carbine (14.5" barrel) you get a ~300m zero as well. If you zero at 25 YARDS, you will be over 5" high at 300 YARDS and will still be high at 300m.
Longer barrels make this worse. |
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Posted: 6/29/2024 11:01:00 AM EDT
[#26]
Quote HistoryQuoted: If you zero at 25 METERS with M855 using an M4 carbine (14.5" barrel) you get a ~300m zero as well. If you zero at 25 YARDS, you will be over 5" high at 300 YARDS and will still be high at 300m. Longer barrels make this worse. You will still have to hit low @ 25 METERS to be on at 300 meters. What is the advertised velocity of the M855 from a 14.5? |
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Posted: 6/29/2024 2:10:34 PM EDT
[#27]
These are the US Army zeroing targets for irons. Notice the different sight settings in the instructions
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Posted: 6/29/2024 5:20:04 PM EDT
[#28]
Quote HistoryQuoted: These are the US Army zeroing targets for irons. Notice the different sight settings in the instructions https://i.ebayimg.com/images/g/3ssAAOSwvA5dFjfp/s-l1200.webp What velocity is indicated from the short barrel? |
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Posted: 6/29/2024 6:29:25 PM EDT
[#29]
Quote HistoryQuoted: What velocity is indicated from the short barrel? I think the official number is 2865 Keep in mind that the US Army considers a gun to be zero'd when all the shots fall within a 4 moa circle around the PoA. That means if the group is within a 12" circle at 300, it's zero'd The same goes with zeroing an ACOG. It's done at 100m and when the shots fall in a 4" circle, it's zero'd |
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Posted: 6/29/2024 7:02:29 PM EDT
[#30]
Quote HistoryQuoted: I think the official number is 2865 Keep in mind that the US Army considers a gun to be zero'd when all the shots fall within a 4 moa circle around the PoA. That means if the group is within a 12" circle at 300, it's zero'd The same goes with zeroing an ACOG. It's done at 100m and when the shots fall in a 4" circle, it's zero'd There is a military video somewhere with a guy explaining how to zero the ACOG at 25 meters using the 300 in the BDC as well. |
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Posted: 6/29/2024 7:56:50 PM EDT
[#31]
Quote HistoryQuoted: The OP has an AR-15A2, so I'm kinda missing why you are bringing in A1 rifles to the discussion? The sights, ammunition and ballistics are different. I'm not really telling him to obtain a true 25M zero, I'm telling him to zero at 25M with the procedure I posted. 36M zero is just the Marine way of zeroing and it does the same thing as the Army way of zeroing at 25M without having to adjust the rear elevation drum to 8/3+1, and then moving it back down to 8/3 after obtaining a zero. The only bad thing I ever heard about a 300M zero is that you are shooting high from 100 - 200 + meters. We just aimed slightly low at the intermediate targets. https://imagizer.imageshack.com/v2/640x480q70/922/lbT3AG.jpg And that graphic just shows how asinine the method the Army taught us really was. Fuck being that high on targets under 200 yards. OP, what distances do you want to shoot that rifle at? Unless you really want to run that thing past 250-300, don't concern yourself with the elevation marks on the rear sight drum. You'll get the most enjoyment out of the thing if you just zero at 50 yards & leave it. |
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Posted: 6/30/2024 12:24:46 PM EDT
[#32]
Quoted: I still enjoy shooting my 30+ year old first AR on occasion, a Pre-ban Colt Sporter (Lightweight) with carry-handle A2 sights. If nothing else it sure helps me appreciate optics on my other rifles. I’ve found that the 50 yard zero is likely the most appropriate for me and my older eyes so I set the distance “wheel” at 8/3 for 300 yards and zero’ed the rifle at 50 yards using the small aperture. A couple of questions: (1) By using the small aperture to zero at 50 yards is the large aperture also zero’ed for 50 yards? Is there any time I would use the larger aperture over the smaller one? (2) I assume that the 50 yard zero makes the additional settings on the distance “wheel” drastically incorrect and rather than use the wheel for distances past about 250 yards I would instead need to use holdovers at various distances? Thanks in advance for help! 1) On a 20” barrel, rifle gas front sight post AR the large peep will be approximately 2.5 MOA lower than the fine peep at any rear drum setting. A four position front sight post has only 1.25 MOA elevation resolution. Those two facts will color any zeroing scheme with respect to theoretical zero crossing of a theoretical (independent of group dispersion) trajectory line. 2) If your elevation drum bottoms out at 8/3 setting then zeroing the fine peep at 50/200ish will throw off the drum calibration. The fix: Search for RIBZ zeroing method. Setting the elevation drum so it works: If you want a 50 yard zero with the fine peep then adding some bottom clicks to the drum below the 8/3 setting will allow for the RIBZ method. You’ll need an Allen key. The RIBZ method lets you zero the fine peep at closer distances than 300. Within the resolution of your front sight and bullet velocity the 8/3 setting of 300 on fine peep, and 50/200ish on large peep is still functional. Longer range drum marks will also be close. Your sight hold (center or pumpkin on fence-posts also comes into play. As a simple approach with fine peep -3 clicks below 8/3 setting zeroed with 6 o clock front post hold with group at bottom of black within the resolution of your front sight adjustment should yield a 50/200ish setting at -2 clicks, and reasonable longer range drum settings for the fine peep. The large peep at 8/3 setting should be close to 50/200ish as designed. https://www.ar15.com/forums/ar-15/RIBZ--Revised-Improved-Battlesight-Zero/18-328143/ |
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Posted: 6/30/2024 1:14:28 PM EDT
[#33]
Quote HistoryQuoted: And that graphic just shows how asinine the method the Army taught us really was. Fuck being that high on targets under 200 yards. OP, what distances do you want to shoot that rifle at? Unless you really want to run that thing past 250-300, don't concern yourself with the elevation marks on the rear sight drum. You'll get the most enjoyment out of the thing if you just zero at 50 yards & leave it. There is also a 200m zero mentioned in FM 3-22x9 for use in urban areas, and how to get it   for irons at 25m it basically works out to: 1" low for M16A2/A4; 1.25" low for M4 |
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Posted: 6/30/2024 3:19:07 PM EDT
[#34]
Quote HistoryQuoted: or, use the 0-200 aperture which has a 200m zero There is also a 200m zero mentioned in FM 3-22x9 for use in urban areas, and how to get it https://live.staticflickr.com/65535/53826254250_db49a9bf62_b.jpg https://live.staticflickr.com/65535/53826254300_2b7fbcdd61_b.jpg for irons at 25m it basically works out to: 1" low for M16A2/A4; 1.25" low for M4 It’s cool that the FM provides for that but far-zero-biased 25M zeroing alone almost always results in correctable windage discrepancies when tested at 100 & 200 yards or meters. For everything but head targets windage is the key accuracy parameter for tall aspect ratio targets (full silhouette or just center chest vitals zone). To me referencing the secondary zero crossing distance just about requires the rifle is shot for confirmation at those extended range targets. As a practical matter the 1.25 MOA (or worse for M4) elevation resolution of the front sight makes these zeroing schemes sort of like precision woodworking: Measure with a micrometer, mark with a crayon, cut with an axe (trajectory model, courseness of sights, dispersion of ammo). |
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Posted: 6/30/2024 3:57:41 PM EDT
[#35]
Quote HistoryQuoted: It's cool that the FM provides for that but far-zero-biased 25M zeroing alone almost always results in correctable windage discrepancies when tested at 100 & 200 yards or meters. For everything but head targets windage is the key accuracy parameter for tall aspect ratio targets (full silhouette or just center chest vitals zone). To me referencing the secondary zero crossing distance just about requires the rifle is shot for confirmation at those extended range targets. As a practical matter the 1.25 MOA (or worse for M4) elevation resolution of the front sight makes these zeroing schemes sort of like precision woodworking: Measure with a micrometer, mark with a crayon, cut with an axe (trajectory model, courseness of sights, dispersion of ammo). |
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