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Posted: 7/15/2026 9:44:44 AM EDT
[Last Edit: TGH456E][Edited]
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@ChemTrailZ You might try the 6652T vs A1 in your uppers, in mine It shot very close. Several threads recently have wondered onto the idea if one ammunition load matches another ballistically out over distance. I've been working on that myself - for a M855A1 clone out to 500yds with an M4A1 and ACOG. I thought I'd post some results for all to consider. Rifle: Krieger 20" NM barrel with just short of 5000rds on it Leupold mk4 on top. Benched- bags front and rear. Method: Used the same aiming point thru out- no adjustments were made. shoot one, dry fire one- slow steady cadence. After each load, the bore was snaked. Just shoot, no adjusting for wind etc. 10 shots each group. NO Chrono results. Conditions: Elevation is around 5541ft Shot two days: (First two groups) - first was warm- 92F, gusty winds 11mph to 15 (Second two groups)-better- 81F, winds 6mph gusting to 14. Photos here: (if you click on them, they enlarge). https://imgur.com/a/zjyWxsm Results: In order of shooting and photos, Center to Center of groups: 5562T vs LC15A1: 0.4 MOA difference LC15A1 vs Clone: 0.8 MOA difference Clone vs LC15A1: 0.48 (1/2) MOA difference LC15A1 vs LC24M855: 0.945 MOA difference FWIW: In wondering down this test road, I did find that these loads would shoot different in my various uppers. So for me the challenge was finding one that was consistent over the different uppers. You really have to just shoot them in yours---- they may or may not shoot the same. Hope it helps. |
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Originally Posted By lysanderxiii: Lot-to-lot differences of the same load can be that different. Pretty exact match. Yes, there are some differences: lots, barrels etc. In other tests, I've used that same barrel/upper to get velocity data for both loads. That'd help answer if that "closeness" stays together out to 500. That is why I posted it, they are close, now 10-well 20- shots is not thorough test but is a good initial example. Shoot 40 of each atleast and run it out to 500. Much better idea of whats going on. |
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Originally Posted By ITCHY-FINGER: WTF are you comparing? Are they lot #s for the A1? I am VERY confused at to what you are comparing. Other than that it looks very thorough and scientific. I'm sorry if I wasnt clear and maybe this information isn't of interest to you. I shot groups of 5562T, M855A1, M855 and a "clone" of M855A1 I use to practice with. I then measured how close those groups were to one-another to see if they shot to the same POI. The point to that was to see if, for example, you could use one zero on a BDC for different ammunition. Or if like some, you had one zero on your rifle, if it would work for multiple loads. ".. 200yd Test: How close are the POI's? 5562T vs M855A1, Clone vs A1, and M855A1 vs M855........" is the title. "....Several threads recently have wondered onto the idea if one ammunition load matches another ballistically out over distance....." |
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Originally Posted By TGH456E: Shot two days: (First two groups) - gusty winds 11mph to 15 (Second two groups)-winds 6mph gusting to 14. 5562T vs LC15A1: 0.4 MOA difference LC15A1 vs Clone: 0.8 MOA difference Clone vs LC15A1: 0.48 (1/2) MOA difference LC15A1 vs LC24M855: 0.945 MOA difference Nice test. Just a question: in the overall MOA difference is it just elevation? Since the wind was blowing harder the POI shifted and groups were "wider". Another thought is if you were to "re-zero" with each ammo at 100yd, maybe the POI at 200yd would not be so obvious. Regardless, are you going to test further? I find that at 300yds is where POI "drop" becomes more obvious. |
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Originally Posted By smoothy8500: Nice test. Just a question: in the overall MOA difference is it just elevation? Since the wind was blowing harder the POI shifted and groups were "wider". Another thought is if you were to "re-zero" with each ammo at 100yd, maybe the POI at 200yd would not be so obvious. Regardless, are you going to test further? I find that at 300yds is where POI "drop" becomes more obvious. Rezeroing for each ammo type would make any comparison meaningless |
| US Army/Marine standards for zeroing an ACOG are for a 3-shot group to be within a 4" circle around the PoA. Depending on how close to the PoA an ACOG was initially dialed in, it seems like switching to any of these loads would still have it be considered "zeroed" |
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Originally Posted By TGH456E: I'm sorry if I wasnt clear and maybe this information isn't of interest to you. I shot groups of 5562T, M855A1, M855 and a "clone" of M855A1 I use to practice with. I then measured how close those groups were to one-another to see if they shot to the same POI. The point to that was to see if, for example, you could use one zero on a BDC for different ammunition. Or if like some, you had one zero on your rifle, if it would work for multiple loads. ".. 200yd Test: How close are the POI's? 5562T vs M855A1, Clone vs A1, and M855A1 vs M855........" is the title. "....Several threads recently have wondered onto the idea if one ammunition load matches another ballistically out over distance....." OK, Im sorry. I read the title and expected M855 vs M855A1 trajectory comparisons but got thrown off my your abbreviations. I think I got it now (after a coffee). Thanks for posting and more ballistic data is always helpful. So the biggest POI difference is between the A1 and M855 (about 1"). I assume the abbreviation "LC15" is the head stamp for 2015 production for M855A1 ammo...with all the variations in pressure/velocity in early A1 lots, do you have any velocity data for it or any loads? Just wondering if the LC15A1 load may be an outlier...? Anyway, with the accuracy of typical M855 and A1 loads (around 3MOA) it's hard to even measure a sub 1" difference in POI. |
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Originally Posted By smoothy8500: Nice test. Just a question: in the overall MOA difference is it just elevation? Since the wind was blowing harder the POI shifted and groups were "wider". Another thought is if you were to "re-zero" with each ammo at 100yd, maybe the POI at 200yd would not be so obvious. Regardless, are you going to test further? I find that at 300yds is where POI "drop" becomes more obvious. No, if you look at the photos (they enlarge when you click on them), well, some are just more-side-to-side than just elevation. In shooting these and other groups like this test, there isn't "rhyme or reason".......... some are side by side, some have an elevation difference- diagonal for lack of better word. Yes, I'd agree that 300+ is really where you see the different drops. I've shot my "clone" out to 500.......... (see above my interest in this) and 855- enough to find they (855 and A1) are NOT matching. I doubt I will go further with the 5562T. Here's one test of mine- this "does it shoot the same" idea: https://www.ar15.com/forums/ar-15/-ARCHIVED-THREAD-200yd-Groups-Velocities-of-Winchester-62OT-mk318-64-GD-and-others-/16-744061/? I have posted others but they seem to have gone into archive. |
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Originally Posted By ITCHY-FINGER: So the biggest POI difference is between the A1 and M855 (about 1") (Yes, but its about 1 MOA, not 1") . I assume the abbreviation "LC15" is the head stamp for 2015 production for M855A1 ammo (Yes, correct)... with all the variations in pressure/velocity in early A1 lots, do you have any velocity data for it or any loads? (Yes, in other tests, I've given velocity data on the A1 I've used) Just wondering if the LC15A1 load may be an outlier...? Anyway, with the accuracy of typical M855 and A1 loads (around 3MOA) ( I'm not sure thats accurate- I mean yes, there are DEFINATELY lot to lot differences but the A1 shot here is about 1.5 MOA and Molon tests it here: https://www.ar15.com/forums/AR-15/-ARCHIVED-THREAD-M855A1-Accuracy-and-Velocity-updated-/16-783286/?page=1) it's hard to even measure a sub 1" difference in POI. (I'd argue the opposite, if you look at my test and the photos, using the "On Target" system, it's easy. You take a photo of your group and in this case both groups and thru that system it finds the Center of each group, then you measure the distance from each center- thus my note of "CTC difference." It doesnt matter if the groups are 2" or 20" it marks the center of each group and then you measure the difference.) See my replies above. |
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Originally Posted By mcantu: US Army/Marine standards for zeroing an ACOG are for a 3-shot group to be within a 4" circle around the PoA. Depending on how close to the PoA an ACOG was initially dialed in, it seems like switching to any of these loads would still have it be considered "zeroed" You're referring to the typical 25 meter zero criteria? I'm loathe to consider, more correctly- using a 25 meter "zero" is at best a guess. IIRC, you are supposed to confirm your 25m "zero," which rarely if ever happens. PS: I looked it up, TC 3-22.9 page E-2: "......ZERO CONFIRMATION OUT TO 300 METERS E-9. The most important step in the zeroing process is zero confirmation out to 300 meters. Having a 25 m zero does not guarantee a center hit at 300 meters. The only way to rely on a 300-m hit, is to confirm a 300-m zero........." |
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Originally Posted By TGH456E: No, if you look at the photos (they enlarge when you click on them), well, some are just more-side-to-side than just elevation. I did look at them, just confusing with dashed lines/circles/squares/colored Cheerios or Froot Loops maybe? Wasn't sure if it was just elevation in relation to the BDC reticle you were looking at. I guess there's no real easy way to plot the different POI's all together. |
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Originally Posted By TGH456E: You're referring to the typical 25 meter zero criteria? I'm loathe to consider, more correctly- using a 25 meter "zero" is at best a guess. IIRC, you are supposed to confirm your 25m "zero," which rarely if ever happens. PS: I looked it up, TC 3-22.9 page E-2: "......ZERO CONFIRMATION OUT TO 300 METERS E-9. The most important step in the zeroing process is zero confirmation out to 300 meters. Having a 25 m zero does not guarantee a center hit at 300 meters. The only way to rely on a 300-m hit, is to confirm a 300-m zero........." Army and USMC manuals both say that the preferred zero distance for the ACOG is at 100. I think what you quoted is from the iron sights section |
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Originally Posted By smoothy8500: I did look at them, just confusing with dashed lines/circles/squares/colored Cheerios or Froot Loops maybe? Wasn't sure if it was just elevation in relation to the BDC reticle you were looking at. I guess there's no real easy way to plot the different POI's all together. Fruit Loops! :) Thats a good one. Yes, in a way it is hard to overlap two 10 shot groups, or actually how to mark them so you dont get confused as to which-shot-is-which. So I used the paper reinforcement "Sticker" ring-thingys. If it helps the center of each group is marked by a + , so look for both of them and you can see their relation to one-another. Then took the photo, used the "On Target" app and done. I wasnt using a BDC reticle BTW, instead a mk4 Leupold with cross hair. Same POA on the center diamond thru out. |
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Originally Posted By mcantu: Army and USMC manuals both say that the preferred zero distance for the ACOG is at 100. I think what you quoted is from the iron sights section Yes zeroing an ACOG (M150) at 100 would make sense but which US Army manual are you referring to? I'd very much appreciate that as a reference. In the mean time I was quoting US Army Training Circular 3-22.9 Rifles and Carbines. Which describes zeroing an M150 at 25meters for example. And No, section E described the correct zeroing procedure for all the sighting systems. But thats why I cited my reference, it's available on line- you can read it if you like. |
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Originally Posted By TGH456E: Yes zeroing an ACOG (M150) at 100 would make sense but which US Army manual are you referring to? I'd very much appreciate that as a reference. In the mean time I was quoting US Army Training Circular 3-22.9 Rifles and Carbines. Which describes zeroing an M150 at 25meters for example. And No, section E described the correct zeroing procedure for all the sighting systems. But thats why I cited my reference, it's available on line- you can read it if you like. "ZEROING THE ADVANCED COMBAT OPTICAL GUNSIGHT 8-44. The adjustment increments for the ACOG are 1/4 inch per click at 100 meters. A click is defined as the sound or feel of the positive detent movement. This means that 4 clicks are required to move the bullet approximately one inch on the target at 100 meters. At 25 meters, 16 clicks move the bullet one inch. Turning the screw in the direction of the arrow moves the bullet impact in the direction marked (up/right). NOTE: To ensure a consistent zero, tap the scope with the palm of your hand to stabilize the adjustment mechanism after an adjustment has been made, and then fire a three-shot group on the target. 8-45. The ACOG scope with chevron reticle is designed to be zeroed at 100 meters, using the tip of the chevron reticle for POA/POI (Figure 8-7). 8-46. For a quick combat zero, the scope may be zeroed at 25 meters, using the tip of the 300-meter post as POA/POI. A 25-meter zero is less precise than a 100-meter zero and should be verified at longer distances once time and a range is available (Figure 8-8)." Then later is the offsets section is says: "NOTES: 1. When zeroing the ACOG (Figure F-10), a 100-meter true zero is preferred. When engaging targets at 200 meters with the ACOG, use the 200-meter aiming point tip (tip at the inside of the chevron), if time allows (Figure F-11). 2. For the ACOG 25-meter zero, Soldiers should use the 300-meter point of aim (tip of the 300-meter post at the target's center of mass) and point of impact (a 4- by 4-centimeter square drawn 1.5 centimeters down from the target's center of mass)." |
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Mcantu: Thanks for the reference, we've been looking at the same one, though I have the 2016/17 version, not the older 2008 one. Both say -roughly- the same thing: Get a 25m initial zero and then confirm it at actual distance. Your 2008 says this for example: 5-58. The 300-meter target can be used to confirm weapon zero or to refine the zero obtained on the 25-meter range. When Soldiers properly compensate for the wind, the zero on this target is more valid than the zero obtained on the 25-meter range. Two Questions for you: Where are you getting this groups in a 4" circle are zeroed (and what distance) comment? Your 2008 reference says this of a 25m zero exercise: 5-45(8) If five out of six rounds fell within the 4-centimeter circle, the Soldier is zeroed and can be removed from the firing line. Where, specifically, does the 2008 version explain to use a 100yd zero? Yes, it describes the ACOG sight adjustments, but that is not a zero. It describes a 100m "feedback" target but not a zero. I mean I agree with you that is the best and obvious choice considering the ACOG reticle. Otherwise it gives two choices of either 200m or 300m for a zero: "*5-50. The 200-meter zero is not an alternate to the 300-meter zero; rather, it is a supplemental zero. The standard 300-meter zero will continue to be used when units are conducting standard rifle qualification or when units are deploying to an area where most engagements occur at distances greater than 200 meters. *NOTE: 200-meter zero procedures mirror those of standard zero procedures, with the exception of the target offsets. See Appendix F for more information about preparing 200-meter zero target offsets for various sights." Thanks again! |
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PS Mcantu: Sir: I'm not sure if you are in the Military or not and honestly that isn't my concern. The reason for my specific questions to you is I am in the Military. And it is SO SO MUCH easier to get training time, ranges and AA&E if you can say: "This training/exercise/thing we are doing is "In Accordance With" this/that regulation or TC or FM etc." People leave you alone and you can get shit done if you can do that. When you cant provide a reference or standard to what you are doing, they ask more questions and it becomes tedious. And maybe for good reason. But that also means you are spending as much, if not more, time justifying what you are trying to do as actually doing it. |
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Originally Posted By TGH456E: PS Mcantu: Sir: I'm not sure if you are in the Military or not and honestly that isn't my concern. The reason for my specific questions to you is I am in the Military. And it is SO SO MUCH easier to get training time, ranges and AA&E if you can say: "This training/exercise/thing we are doing is "In Accordance With" this/that regulation or TC or FM etc." People leave you alone and you can get shit done if you can do that. When you cant provide a reference or standard to what you are doing, they ask more questions and it becomes tedious. And maybe for good reason. But that also means you are spending as much, if not more, time justifying what you are trying to do as actually doing it.   The 4" at 100 standard came from the USMC Rifle Marksmanship Manual MCRP 8-10B.2  
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Originally Posted By DevL: I have seen 1 MOA shifts from different lots of the same ammunition. Those are very close. But your BDC is Atleast that is what I've found, though part of that is in my case I'm shooting around 5400ft elevation. But also as was brought up in comment #6 around 300 if the velocities or BC are different, they will diverge as well for those reasons. |
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Originally Posted By TGH456E: Atleast that is what I've found, though part of that is in my case I'm shooting around 5400ft elevation. But also as was brought up in comment #6 around 300 if the velocities or BC are different, they will diverge as well for those reasons. Factors Causing a Battlesight Zero Reconfirmation Marines are responsible for maintaining a BZO on their Service rifles at all times. Factors that can influence the BZO of a Service rifle to change on a daily basis include atmospheric conditions, humidity, and temperature. If operating in a combat environment, Marines should confirm their BZO as often as possible. To confirm a BZO, the Marine can begin the zeroing process by using the previously established BZO sight settings rather than placing the sights at initial sight setting. Maintenance, temperature, climate, ammunition, ground elevation, and uniform will cause a BZO to need to be reconfirmed. Maintenance It is possible for the BZO to change if ordnance personnel perform maintenance on a Service rifle. If maintenance was performed, it is critical that the Service rifle be rezeroed as soon as possible. Temperature An extreme change in temperature (i.e., 20 degrees or more) will cause the elevation BZO to change. Changes in temperature cause chamber pressure to increase when hot and decrease when cold, causing shots to impact the target high in hot temperatures and low in cold temperatures Climate Changing climates (e.g., moving from a dry climate to a tropical climate) can cause fluctuation in air density, moisture content, temperature, or barometric pressure and affect the Service rifle’s BZO. Ammunition Inconsistencies in the production of ammunition lots can change a Service rifle’s BZO. Ground Elevation Drastic changes in ground elevation can create changes in air density, moisture content, temperature, or barometric pressure, affect the Service rifle’s BZO. Uniform If Marines zero their Service rifles in utility uniform and fire in full battle gear, their BZOs can change. The wearing of full battle gear changes eye relief, placement of the Service rifle in the shoulder pocket, and the way the Service rifle is supported on the rail system. Marines must establish their BZOs while wearing the uniform and equipment that they will be wearing while engaging targets. |
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Originally Posted By mcantu: From the USMC manual: Factors Causing a Battlesight Zero Reconfirmation Marines are responsible for maintaining a BZO on their Service rifles at all times. Factors that can influence the BZO of a Service rifle to change on a daily basis include atmospheric conditions, humidity, and temperature. If operating in a combat environment, Marines should confirm their BZO as often as possible. To confirm a BZO, the Marine can begin the zeroing process by using the previously established BZO sight settings rather than placing the sights at initial sight setting. Maintenance, temperature, climate, ammunition, ground elevation, and uniform will cause a BZO to need to be reconfirmed. Maintenance It is possible for the BZO to change if ordnance personnel perform maintenance on a Service rifle. If maintenance was performed, it is critical that the Service rifle be rezeroed as soon as possible. Temperature An extreme change in temperature (i.e., 20 degrees or more) will cause the elevation BZO to change. Changes in temperature cause chamber pressure to increase when hot and decrease when cold, causing shots to impact the target high in hot temperatures and low in cold temperatures Climate Changing climates (e.g., moving from a dry climate to a tropical climate) can cause fluctuation in air density, moisture content, temperature, or barometric pressure and affect the Service rifle’s BZO. Ammunition Inconsistencies in the production of ammunition lots can change a Service rifle’s BZO. Ground Elevation Drastic changes in ground elevation can create changes in air density, moisture content, temperature, or barometric pressure, affect the Service rifle’s BZO. Uniform If Marines zero their Service rifles in utility uniform and fire in full battle gear, their BZOs can change. The wearing of full battle gear changes eye relief, placement of the Service rifle in the shoulder pocket, and the way the Service rifle is supported on the rail system. Marines must establish their BZOs while wearing the uniform and equipment that they will be wearing while engaging targets. This is excellent info and surprisingly detailed (for a military FM). My military time (Army) was all irons and Im 100% sure that if I ever asked anyone about changes in zero from humidity or elevation, I would have been mocked mercilessly. In my time in the Army Reserve, often being stuck with sub-optimal civilian ranges, I zero'ed rifles and even an M60 at 25 yards. (Getting time on an actual military range was heaven) With the Pig, I fired at a big paper target with little tiny figures of different sizes compensated to equal various ranges. We'd fire a belt of 3 rounds per the little figure and get qualified based on the hits. Same with the M16A1, it was mostly at 25 yards/meters. I'm sure Marines on the ships, practicing on flight decks or wherever do similarly. On a side note, I just tried some Winchester 200 round bulk packs of M855. It had LC26 headstamps along with the usual NATO cross. The ammo shot surprisingly well holding 2MOA for numerous 5 shot groups (sandbag rest). I dont remember M855 shooting this well for me in the past. |
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