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RIBZ - - Revised Improved Battlesight Zero (Page 3 of 11)
Added comments are in red.
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You could run an 8-36x3/16 allen screw up into the FSB to secure the wobbly post. If your FSB is not tapped all the way through to the bottom, it's really not a big deal to finish that job from the top after removing the post. You'll have to cut down the short leg on the appropriate allen wrench in order to start the allen screw in the FSB. There's just not a whole lot of working room down there. Ask me how I know. 
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Politicians and diapers need to be changed often and usually for the same reason
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molon, Just a question. I have been running the 50/200 zero without the adjusting of the elevation wheel for IBZ. It has been working fine on one rifle, and I don't mind not having the elevation wheel calibrated. On one carbine, I have a similar problem as mentioned above with the front sight post. Mine is the bushmaster tall post, and it has to be out to the point it is loose to get a 50 yd zero. 2-3 rotations down, it is fine. If I were to do the adjustments to the elevation wheel (6/3) would that help with the front sight adjustment? I am considering going back to the 25m zero on this carbine if that doesn't work. |
Added comments are in red.
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When are you going to use the large aperture at longer distance? |
I just noticed that this is all dependent on M855 ammo!!! I have some M855 ammo that I am planning on sighting in with, but how will this affect my cheapo Wal-Mart Remington .223 55Gr ammo? I buy a couple boxes ever so often just because it is cheap and I don't have to pay shipping on the good stuff. I think the .223 ammo from Remington has about 1000 fps less velocity and a little lighter bullet. Should I sight it in with M855 so that my sights are correct and then assume I cannot shoot as far with the .223? Maybe use the .223 for 50 yard target practice? I used the ballistics calculator program from Remington and if I sight in at 50 with the 55Gr .223, it will be zeroed at like 150 yards, not much velocity in the .223 apparently, so it is dropping off quickly. I wonder how far off it would be at 50 yards if I sight it in with M855. This really stinks. I guess if the rear was not adjustable it wouldn't even matter, I could sight in using the .223, but since it is designed around the M855, then it makes all the difference how I sight in and what I shoot. Is it possible to figure out how the .223 shoots based on sighting in for the M855? |
"There's only three things he (Republican presidential candidate and former New York City Mayor Rudy Giuliani) mentions in a sentence: a noun and a verb and 9/11." -- Sen. Joseph Biden, speaking at a Democratic presidential debate.
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Molon- Absolutely outstanding info, as usual. I was an early user of the IBZ and now will use the updated RIBZ to be able to compete more successfully in 100-yd matches. Amazing that I actually won a few of these contests using the old IBZ and was "guessing" where the POI would be at 100M, usually having to aim a few inches lower. Not much room for error when shooting at smallish targets. Obviously, once you have the new open sights set up at 100M, ammo type/grain size/5.56 vs .223 loads all will have a lot to do with where the ultimate POI is on the paper. Here's a question: I just ordered a new RRA National Match upper 1/8 20" S/S barrel with 1/4" MOA adjustment sights for both windage and elevation. As I understand it, the standard A2 sight clicks are 1" MOA for elevation and 1/2" MOA for windage. If that is true, then I need to set my new RRA N/M rear sights by multiplying that "4 clicks up" as recommended for the RIBZ by 4 (total of 16 x 1/4 MOA clicks), since my new sights are giving me 4 x 1/4" MOA clicks for the usual 1" MOA click on the standard A2 rear drum sight, correct? Let me know if I have this right. Thanks again for the great info. Regards, capt.john phoenix27 |
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Bump for a thread that should be tacked... And I'm doing my A2 with this method today. Rmpl |
"Our destruction... will be from another quarter. From the inattention of the people to the concerns of their government, from their carelessness and negligence..." ...Daniel Webster, June 1, 1837
What Would Yahshua Do? www.wwyd.org
What Would Yahshua Do? www.wwyd.org
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All hail Jeanne Assam!
Thanks Molon! |
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Here is a down-loadable target in .pdf format that can be used for zeroing 20" uppers with A2 sights at 50 yards using the Improved Battlesight Zero. The dashed vertical grey lines represent one click of the windage knob. The dashed horizontal lines represent one click of the FRONT SIGHT POST. 50 yard zeroing target When printing, you need to have the "page scaling" option in Adobe Reader set to "none" in order for the target to print with the correct dimensions.  |
All hail Jeanne Assam!
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Hey, first post on this forum...though I've been reading it for months! I zeroed my 16in DPMS M4 with 55gr FMJ Remington and a detachable rear DMPS Sight (my first build :) ) using the RIBZ technique yesterday. It works great!! My only question is, the IBZ remains intact at 50/200, the 6/3 setting gets me hits at 25, however when i set it to 6/3 -6 (for the RIBZ) setting for 100 yds, it hits 3.5 inches low. It works perfect at 6/3 -5. Did I set something up wrong? Any input would be appreciated:) Thanks |
I don't know why there would be a 3.5 MOA change with one click of your rear sight, but all that ultimately matters is that you know what settings on your sights are needed to obtain your desired point of impact at a given distance. |
All hail Jeanne Assam!
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I did the IBZ to my rifle and it goes 2.5 (moves past -2 but not enough to "click". When I set it -3 it was a full click there but a 1/2 click shy of 1 click over the 8 on the big end) clicks below the 8/3 on the 3 setting but 1 full click above the 8/3 on the 8 setting. I would think it would be in whole-clicks. Is this acceptable or is something wrong? It does give me a "buffer" zone to be sure I am at a TRUE -2 clicks, just want to be sure I didn't mess up somewhere. Any thoughts? |
I guess my situation is normal then, as the 8/3 -2 is technically my new 8/3. Took the above from the TM, what do you guys think. I say normal. |
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I need some help w/ the RBIZ. The first set of pics shows the rifle using the RIBZ in conjunction with BH red box 55gr ammo at 50 and 100 yards. The second set of pics shows the same rifle using the RIBZ using Winchester M855 at 50 and 100 yards. I was wondering if any body could help me tighten up my groups using the M855.  55gr @ 50yds, Standing up  55gr @ 100yds using bench and sandbags  M855 @ 50yds one magazine standing and the other sitting  M855 @ 100yds using bench and sandbags (this is one of worst groupings I've ever shot) Info on the rifle: LMT 10.5" upper using a KAC NT-4 QDSS, standard "F" front sight (it still has the original front post, don't know size) and LMT BUIS. Thanks, Marco |
There are too many variables involved to provide any definitive statements. It could well be something as simple as your barrel just doesn't "like" the M855 load (Occam's razor and such.) |
All hail Jeanne Assam!
0-2
There seems to be some confusion around here as to the function of the “0-2” large aperture of the A2 rear sight. The field manual for M16A1 and M16A2 Rifle Marksmanship states, “The larger aperture, marked 0-2, is used for moving target engagement and during limited visibility. The unmarked aperture is used for normal firing situations, zeroing and with the elevation knob for target distances up to 800 meters. The unmarked aperture is used to establish the battlesight zero.” That’s pretty straightforward. Using a digital caliper, the diameter of the small aperture of the A2 rear sight measures approximately .070”. The large (0-2) aperture has a diameter of approximately .200”. No confusion there. To use the 0-2 large aperture, simply push forward and down on the small aperture portion of the sight leaf to snap the large, 0-2 aperture up into place. That couldn’t get much easier. The confusion surrounding the use of the 0-2 large aperture seems to stem from a misunderstanding of the amount of elevation change involved when changing from the small aperture to the large aperture. The small aperture is intended to be zeroed for a 300 meter zero using M855 fired from a 20” barreled M16A2. The 0-2 large aperture is intended to provide a 200 meter zero, when the small aperture has been properly zeroed with M855 from a 20” barreled M16A2. If you examine the trajectories of M855 fired from a 20” barreled M16A2 zeroed at 300 meters, and at 200 meters, you will see that the difference in elevation between these two trajectories (and hence the difference in elevation between the small and large apertures) is 2.5 MOA. 
To demonstrate this concept, I fired two 10-shot groups from a 20" Colt AR-15, using the standard A2 iron sights, from the bench at a distance of 50 yards using the small aperture. I then flipped the rear sight to the 0-2 large aperture and fired another two 10-shot groups (all groups were fired on separate targets.) The two sets of groups were overlayed on each other to form 20-shot composite groups using RSI Shooting Lab and analyzed to determine the statistical center of their points of impact. In a perfect world, the groups fired using the 0-2 large aperture would have the center of their points of impact 2.5 MOA (1.25” at 50 yards) below the center of the the points of impact of the groups fired using the small aperture. The 20-shot composite group formed from the 2 groups fired using the 0-2 large aperture had a center of point of impact 1.01” below the center of point of impact of the 20-shot composite group fired using the small aperture. 1.01” at 50 yards is 2.02 MOA; not exactly 2.5 MOA, but within a half minute of angle and well within my margin of error using the A2 iron sights. As a side note, the groups fired using the 0-2 large aperture were 144% larger than the groups fired using the small aperture. 
The shift will definitely be greater with carbines due to the shorter sight radius. I’d like to thank Hallorann for sending me a link to the XS Sights (formerly Ashley Express) website where there is some information that may shed some more light on this subject. I have not experienced this myself and therefore cannot vouch for the validity of the information, but according to XS Sights there are three different A2 rear sight leafs on the market that have different elevation offsets; however, XS Sights does not state which manufacturers/models use which rear sight leafs. (My experience with the A2 sights has been strictly with Colt 20" models and they have all had the 2.5 MOA offset for the 0-2 large aperture, and yes, I drank the Kool-Aid. )
According to XS Sights: “Comparing some of the rear sights available today there appears to be 3 variations available. The 1st style (and oldest) has a .014 offset. This gives a 2.52 inch shift in point of impact at 100 yards between the two apertures. The 2nd style has a .017 offset, which shifts point of impact 3.06 inches at 100 yards. The 3rd style has a .024 offset giving a 4.36 inch shift in P.O.I. All of the points of impact shifts shown above are for the standard barrel AR-15/M-16 that has a sight radius of 20 inches. The shorter sight radius (14.5 inches) of the M4 carbine and weapons of similar configuration increase the amount of point of impact shift. The shifts for these shorter sight radius weapons are 3.48, 4.25, 5.96 inches respectively. The only reason for the various shifts would be for changes in the ammunition used by the military over the course of this weapons employment.” The last statement in the above quote seems rather odd to me, as M855 still is, and always has been the standard issue ammunition since the adoption of the M16A2. Also, I don't see any particular use for the 3.06 MOA and 4.36 MOA offsets for a 20" barrel. With the small aperture properly zeroed for 300 meters, the 3.06 MOA offsett will produce a 165 yard zero and with the 4.36 MOA offset, the bullet will never cross the line of sight. 20" barrel with M855 zeroed for 300 meters 
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All hail Jeanne Assam!
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The shift will definitely be greater with carbines due to the shorter sight radius. I’d like to thank Hallorann for sending me a link to the XS Sights (formerly Ashley Express) website where there is some information that may shed some more light on this subject. I have not experienced this myself and therefore cannot vouch for the validity of the information, but according to XS Sights there are three different A2 rear sight leafs on the market that have different elevation offsets; however, XS Sights does not state which manufacturers/models use which rear sight leafs. (My experience with the A2 sights has been strictly with Colt 20" models and they have all had the 2.5 MOA offset for the 0-2 large aperture, and yes, I drank the Kool-Aid.) According to XS Sights: “Comparing some of the rear sights available today there appears to be 3 variations available. The 1st style (and oldest) has a .014 offset. This gives a 2.52 inch shift in point of impact at 100 yards between the two apertures. The 2nd style has a .017 offset, which shifts point of impact 3.06 inches at 100 yards. The 3rd style has a .024 offset giving a 4.36 inch shift in P.O.I. All of the points of impact shifts shown above are for the standard barrel AR-15/M-16 that has a sight radius of 20 inches. The shorter sight radius (14.5 inches) of the M4 carbine and weapons of similar configuration increase the amount of point of impact shift. The shifts for these shorter sight radius weapons are 3.48, 4.25, 5.96 inches respectively. The only reason for the various shifts would be for changes in the ammunition used by the military over the course of this weapons employment.” The last statement in the above quote seems rather odd to me, as M855 still is, and always has been the standard issue ammunition since the adoption of the M16A2. Also, I don't see any particular use for the 3.06 MOA and 4.36 MOA offsets for a 20" barrel. With the small aperture properly zeroed for 300 meters, the 3.06 MOA offsett will produce a 165 yard zero and with the 4.36 MOA offset, the bullet will never cross the line of sight. 20" barrel with M855 zeroed for 300 meters |
All hail Jeanne Assam!
| I swear, on my middie on the CCH I got, the shift was like 4" at 25 meters!!!! The one on my colt doesn't seem as drastic, but it's a 20"er also. Maybe I'll see what this CCH does on my carbine and steel the one from my colt as I don't shoot it as much. And if I swapped it would be less. Or get an A1 ap for my 20"er and try it out some. I don't know. But next time I shoot my carbine, I'll do a similar test to see how much it shifts. |
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Thank you, Molon, for illustrating and explaining these concepts over the course of this thread. You have created a very valuable resource here.
As referenced by Molon, the XS Sights page claims that an A2 aperture offset may be any one of three different variations (0.014, 0.017, or 0.024). They also make POI shift predictions based on these offset measurements combined with either a 20" or a 14.5" sight radius. That is all well and good, but how do we know which of the three offsets we have? How do we know that these predictions are correct? What was used to arrive at these conclusions? We will start with a very useful formula to keep handy - the Elevation Correction Formula. It is as follows: To determine the correct sight height to correct an elevation problem, multiply the sight radius by the elevation error and then divide the results by the distance to the target, in inches. Example (pistol values): Sight radius 5 3/4" = 5.75 Shooting 5 inches low Distance to target 25 feet or 300 inches 5.75 X 5 divided 300 = .09583 The front sight would have to be lowered .096 inch or the rear sight raised that amount (or a combination thereof) to raise the point of impact. What does this have to do with A2 aperture offsets? Based on this formula, an algebraic equation can be expressed as follows: (A) Aperture offset (defined as the difference in height between the centers of the apertures) Is equal to (R) Sight radius in inches Multiplied by (S) POI Shift in MOA Divided by 3600 (100 yards in inches) A = RS/3600 This tells us the aperture offset when we know the values of (R) Sight radius and (S) Shift in MOA. The value for (R) will be easy enough (either 14.5 or 20), but how do we know the value for (S)? Well, since the normal dispersion of fire combined with the use of iron sights will preclude nailing down this value with any degree of accuracy, we must reconfigure the above equation to solve for S (POI Shift in MOA). This yields the equation as follows: S = 3600A/R This is what we need. We need to know the POI shift in MOA. However, in order to solve this equation, we must have a value for (A) Aperture offset. Since this can be multiple values (0.014, 0.017, or 0.024), it will be necessary to physically measure the offset of the particular apertures so that the POI shift for a particular rifle can be determined. I measured the offset of my Colt's A2 apertures in order to determine what offset I am dealing with (0.014, 0.017, or 0.024). I took this measurement relative to the top of the rear sight base (in other words, the top of the uprights that are to either side of the aperture). It is important to measure relative to the top of the base because the heights of the aperture rings do not match - here I am referring to the top of the steel ring, not the top of the hole. Obviously, what must be measured is the center of the hole of the apertures relative to each other. I used a digital caliper to measure the smaller aperture hole for a result of 0.065. This number is divided by 2 to obtain 0.033. Then I placed a steel straightedge across the top of the base (a steel ruler should also work), and measured from the top surface of the straightedge to the TOP of the aperture hole (steel to steel contact) for a result of 0.283. This number is added to 0.033 to obtain 0.316, which is the distance from the top of the straightedge to the CENTER of the small aperture. Next, the same procedure is used for the large aperture hole. I found the hole to measure 0.195, divided by 2 is 0.098. The distance from the top of the straightedge to the TOP of the hole was 0.233, which when added to 0.098 is 0.331. The difference between 0.331 and 0.316 is 0.015, which is the aperture offset, and is damn close to 0.014. It will be necessary to measure very carefully, and to use a true (uniformly flat) straightedge because the offset differences are within a few thousandths of an inch. Now, the XS Sights page is giving us the POI shifts for the (in this case) 0.014 offset. According to them, the POI shift for a 20" sight radius will be 2.52 MOA, and the shift for a 14.5" sight radius will be 3.48 MOA. If we plug these values into the equation S = 3600A/R, we multiply 3600 x 0.014 to get 50.4. We then divide 50.4 by either 20 (rifle) to get 2.52 MOA, or 14.5 (carbine) to get 3.48 MOA. Let's say that you used the small aperture to zero at 50yd, but you want to flip to the large aperture for faster sight acquisition at close range. Now that we are able to define the POI shift in MOA, we can use the elevation adjustment values (given in the Colt Owner’s Manual) to determine how many clicks of the rear sight elevation wheel are needed to compensate for the shift. Note: the following assumes an aperture offset of 0.014. If your offset is different, use the equation to find the POI shift, and divide that number by the MOA value for each click in elevation. For a 20” sight radius with A2 upper, the elevation clicks are worth 1.00 MOA each, and the POI shift between apertures is 2.52 MOA. Divide 2.52 by 1.00 to get 2.52. Adjust the elevation wheel UP either 2 or 3 clicks to maintain the same zero when changing from small to large aperture. For a 20” sight radius with removable handle, the elevation clicks are worth 0.53 MOA each, and the POI shift between apertures is 2.52 MOA. Adjust the elevation wheel UP 5 clicks to maintain the same zero when changing from small to large aperture. For a 17.25" sight radius with A2 upper, the elevation clicks are worth 1.215 MOA each, and the POI shift between apertures is 2.92 MOA. Adjust the elevation wheel UP either 2 or 3 clicks to maintain the same zero when changing from small aperture to large aperture. For a 17.25" sight radius with removable handle, the elevation clicks are worth 0.585 MOA each, and the POI shift between apertures is 2.92 MOA. Adjust the elevation wheel UP 5 clicks to maintain the same zero when changing from small to large aperture. For a 14.5” sight radius with A2 upper, the elevation clicks are worth 1.43 MOA each, and the POI shift between apertures is 3.48 MOA. Adjust the elevation wheel UP either 2 or 3 clicks to maintain the same zero when changing from small to large aperture. For a 14.5” sight radius with removable handle, the elevation clicks are worth 0.65 MOA each, and the POI shift between apertures is 3.48 MOA. Adjust the elevation wheel UP 5 clicks to maintain the same zero when changing from small to large aperture. Hallorann Little Rock |
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4 MOA on a carbine. That's what I figured out mine to be today. I was only shooting at 50 yards though. But I zero'd it at 25 meters. Shot 10 shots at 50 with the small ap, and 10 shots at 50 with the big ap. Found the center of the groupings vertically, measured the difference and it came out to 1-7/8". So, I'll call it a 4 MOA shift. That aint too bad. At least now I know. small ap at 50 Big ap @ 50 Believe me, I'm not braggin about my groups either. But, it is what it is. I didn't have the rear bagged and I was using Federal AE 55 FMJ. Which I'm new to this carbine and don't even know what ammo it really likes. Here's the target I zero'd on: I figure it's good enough for a GP carbine. I also put out 3 clay pigeons in a triangle shape at 100 yards. I tried to put them in a triangle about big enough to represent the kill zone one a deer. I wanted to know if I could effectively hit with the big ap at that range. So I shot standing, using the big ap and nailed one of the clays on the first hit. I put ten rounds real quick in from what I could tell an effective size of deers boiler room. I was happy with that. I'm pretty skeptical that I could hit effectively at 200 yards with the big ap though. At least standing. I think any distance shooting should be done with the small ap. But if it was a low light situation and up fast and furious, the Ghost ring is probably plenty good. Probably even out to 100. Maybe I'll have to try the ghost ring at 200 sometime and go prone or kneel and see if I could hit anything. I think better ammo would probably do a little better, although I'm not sure if it's the ammo. I'm pretty rusty. I like the feel of the carbine with the A1 buttstock on it. I'm not sure I'm going to keep it, but I like it. I like the lighter weight of a collapsible and if I get one, I'll just get a 9mm buffer. I've got something else to say. When shooting just irons, I think the longer sight radius of a rifle is worth it's weight in Gold. I'm not going to whine about this, but I know it makes a difference. That's just something to chew on. I realize everyone and their brother has an optic nowadays, but still thought I'd mention it. I think I could be deadly with training with this carbine though. Even with just the irons. But I would probably be better served with an optic. I really want an ACOG. So much I'm debating on selling my Recce upper for one. |
Uh....the Marines were pretty much doing that in the 80's. Our sights were always set up different than army. 8/3-2 was zero setting shot at 200 meter line on the KD range. Not to take anything away from this illuminating thread because I've been confused and baffled with sight settings before. heck I didn't know that there was a center shift between the two sights for years, I thought it was just for poor light and Oh shit distance engangements. I should print a lot of this out and run the numbers on the range and make my own spread sheets. |
Outstanding!! 
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All hail Jeanne Assam!
Strong work! Your 1 7/8" shift would be 3.75 MOA; look how close that comes to the theoretical shift of 3.48 MOA. |
All hail Jeanne Assam!
Yeah, I'm sure there was some user error. So, it's probably the ap that is supposed to be 3.48 MOA. I can live with that. I'm finally totally comfortable with my A2 Sight. Although I admit, I didn't see how how it will be hitting at 100 with the small ap. I guess that'll be my next thing. But I was happy with at least "combat" type accuracy with the big ap. It appears that with the big ap it's probably going to be a little high at 100 and then with the small ap it will probably be about 4-5" high. Maybe I'll get real anal and shoot some all bagged up real good at 100 and see where it hits. |
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I just finished putting together a mid-length gas system frankengun (I owe credit to PK Firearms for the upper build). It has the aforementioned mid length gas system, a PRI flip up front sight and a RRA Dominator2 BUIS (6/3 wheel). I have already adjusted the elevation wheel for 6/3 -8 and set a mechanical zero and quickly checked with a laser bore sighter to be sure I was in the ballpark. My question: With the mid length system, should I expect any notable differences in clicks when adjusting for range after I set zero following RIBZ procedure? I would think that because the mid-length's sight radius (17.5" I believe?) is between that of a carbine (14.5") and a rifle (20") that I could probably use the settings for a carbine to adjust for range with minimal error. Unfortunately, I rarely have the opportunity to get to the range, let alone a rifle range. If somebody could offer there experience using the RIBZ with a mid-length platform, I would be grateful. joe |
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Quick question, I have a Bushy A2 set for RIBZ at 8/3-3 . I just acquired a RRA NMA2 with 1/4" x 1/4" rear sight. Do I need to double the number of clicks to 8/3-6 assuming I initially set the elevation drum offset at 6 clicks for my 100yd zero? I wasn't sure if the theread was assuming 1/2" x 1/2" sights. Tnx--
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RIBZ - - Revised Improved Battlesight Zero (Page 3 of 11)
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