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Posted: 8/4/2019 9:27:25 AM EDT
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I recently got several Holosun 403R reddot sights for a couple of ARs. I took one to the range for the first time today, and sighted it in. At the particular distance I sighted it (about 10 yards), it worked perfectly. I went to confirm the zero at 20 yards, and it was way off. I zeroed at that distance, and it was fine. When I moved the target closer, it was way off again. I got home and zeroed the scope to a laser bore sight at about 5 yards. Leaving the bore sight in the chamber, I looked through the red dot and aimed around the room. The laser and dot diverged substantially at different distances. I tried my other Holosun (same model), and it exhibited the same behavior. I had both sight mounted near the front of the upper, and the divergence happened with both eyes open, as well as just one eye open. I tried this with my scope (Nikon m223 2-8x), and also got the same divergence. What am I doing wrong. Is there a minimum distance I have to sight the guns at? If so, then how can I rely on the red dot for HD, where the range would be extremely short? Thanks for any info. |
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A bullet does not travel in a straight line. It sort of "lobs" to the target. So when you zero it with a laser sight, what you're doing is aligning the barrel to the reddot. That isn't to say the bullet is going to go there, but rather the bore is aligned with the dot. For 5.56 ammo, it depends on the range you're at. If your range is a 25 yard range, then a 25 yard zero is good enough. If it can go out to 100, I recommend zeroing at 36 yards as it seems to be the best value overall. Check out this article for better explanation: http://www.thenewrifleman.com/maximum-bullet-flight-getting-the-most-out-of-ar15-zero/ I recommend a app called the strelok pro that you can get for your iPhone or Android. You simply enter the bullet data and the optic you have (reddots don't matter which one you choose) and you know where to aim to get the desired zero at whatever yard. Pro tip: train with the same exact ammo, always. So if you like Federal XM193, always shoot that. Never use anything else. Shoot as close and as far as you can. That way you know the bullet 100% always. |
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Originally Posted By mx597turbo:
I recently got several Holosun 403R reddot sights for a couple of ARs. I took one to the range for the first time today, and sighted it in. At the particular distance I sighted it (about 10 yards), it worked perfectly. I went to confirm the zero at 20 yards, and it was way off. I zeroed at that distance, and it was fine. When I moved the target closer, it was way off again. I got home and zeroed the scope to a laser bore sight at about 5 yards. Leaving the bore sight in the chamber, I looked through the red dot and aimed around the room. The laser and dot diverged substantially at different distances. I tried my other Holosun (same model), and it exhibited the same behavior. I had both sight mounted near the front of the upper, and the divergence happened with both eyes open, as well as just one eye open. I tried this with my scope (Nikon m223 2-8x), and also got the same divergence. What am I doing wrong. Is there a minimum distance I have to sight the guns at? If so, then how can I rely on the red dot for HD, where the range would be extremely short? Thanks for any info. Here is something for you to read. |
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Here's a really good article for you: https://www.shootingillustrated.com/articles/2012/4/10/zero-distance-for-a-home-defense-ar-15/
It explains how off you'll be depending on how you zero your rifle. Again, it's about choosing one zero, always picking the same ammo, and practicing. If you change from 55gr to 77gr, for example, your zero is now way off again. You'll have to figure it all out again and re-zero your optic. But again, if you trained a lot and know where the bullet will go relative to your 55gr zero at yard X, then you'll know where your 77gr projectile will go. |
| Thanks for the info. My issue is that there is a divergence between the laser and the sight/dot at different distances. For example, if I align the sight/dot to the laser at 15 feet, and i point the gun at a wall 10 feet away, the laser and sight/dot are no longer aligned. |
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Originally Posted By mx597turbo:
Thanks for the info. My issue is that there is a divergence between the laser and the sight/dot at different distances. For example, if I align the sight/dot to the laser at 15 feet, and i point the gun at a wall 10 feet away, the laser and sight/dot are no longer aligned. And yes, aiming at something 15 ft away is going to be drastically different than aiming at something 10 ft away. A rifle round is not shooting in a straight line. |
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Few things to remember is what the previous posters stated, height of bore, and knowing your holds for the zero you shoot. Height of bore you have to consider the barrel and optic are not on the same plane so close in depending on zero you will have to account for that. If you want to understand it better place the muzzle of your barrel in the bullseye of a target and look where your sight is aligned in relation to the barrel/bullseye. Knowing your holds I cannot seem to find the video but maybe someone can post it where it is explained your impacts depending on your zero. |
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Yeah you're doing it all sorts of messed up haha
These pictures should illustrate the problem to you, you're sighting in at one point on the bullet path, but bullets don't travel in a straight line as you would expect. Most people sight in at 25 yards or 50 yards or 100 yards. Also you need to consider the height of the red dot relative to the bore axis, as you get closer to targets the bullet is going to shoot below where the dot is. |
"Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety." -Benjamin Franklin
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Originally Posted By mx597turbo:
Thanks for the info. My issue is that there is a divergence between the laser and the sight/dot at different distances. For example, if I align the sight/dot to the laser at 15 feet, and i point the gun at a wall 10 feet away, the laser and sight/dot are no longer aligned. Do yourself a favor and throw away the boresight. This is exactly what people meant when they say you better spend money on ammo and training. Get a 1000 pack of XM193 ammo, hit the range, and don't come out until you figure out where the bullet will be at each yardage. |
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Originally Posted By dalle0001:
And yes, aiming at something 15 ft away is going to be drastically different than aiming at something 10 ft away. A rifle round is not shooting in a straight line. |
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Originally Posted By mx597turbo: If that's the case, then how can a red dot be used for SD/HD? If I can't hit a target at 10 feet, because I zeroed at 15 feet, how can I trust this type of optic? I would think the red dot would be fine withing a range of maybe 5ft - 50ft. If a different of 5 ft is enough to be completely off target, I'm just going to stick to iron sights. As I said, train, train, train, train, train, train, train, train, train, train, train, train, train. Did I mention train? Take it to the range and train, train, train, train, train. Imagine this: your boresight is in the dumpster and you're driving in your car to the range because it's training time! And to answer your question, you're not off by say 40 inches. You're only off by a few inches. Be it 3-5 inches. So if you know this, which you would if you actually trained with it instead of violating your rifle with boresights, you wouldn't be that far off in a HD/SD situation. Edit: And as a final thought for you a bore sight is never the same after you remove it from the bore or muzzle! It's built to some tolerance and depending on what type of boresight you have (bore or muzzle that you slip on), you might be off! Hopefully by now the boresight is in the dumpster and you're heading to the range. |
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Originally Posted By mx597turbo: If that's the case, then how can a red dot be used for SD/HD? If I can't hit a target at 10 feet, because I zeroed at 15 feet, how can I trust this type of optic? I would think the red dot would be fine withing a range of maybe 5ft - 50ft. If a different of 5 ft is enough to be completely off target, I'm just going to stick to iron sights. |
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Originally Posted By mx597turbo:
If that's the case, then how can a red dot be used for SD/HD? If I can't hit a target at 10 feet, because I zeroed at 15 feet, how can I trust this type of optic? I would think the red dot would be fine withing a range of maybe 5ft - 50ft. If a different of 5 ft is enough to be completely off target, I'm just going to stick to iron sights. Originally Posted By mx597turbo:
Originally Posted By dalle0001:
And yes, aiming at something 15 ft away is going to be drastically different than aiming at something 10 ft away. A rifle round is not shooting in a straight line. Trust the guys here telling you to zero at 50 or 100 and then go shoot it at varying distances. You'll find that your point of impact will only be a few inches low at maximum when at the muzzle and the discrepancy will decrease as you approach your zero distance. This is easily accounted for and practicing high thoracic holds are better anyway as people often tend to aim low-ish (center of the person's visible mass = lower torso = gut shot). |
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Originally Posted By mx597turbo: If that's the case, then how can a red dot be used for SD/HD? If I can't hit a target at 10 feet, because I zeroed at 15 feet, how can I trust this type of optic? I would think the red dot would be fine withing a range of maybe 5ft - 50ft. If a different of 5 ft is enough to be completely off target, I'm just going to stick to iron sights. Attached File |
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Originally Posted By mx597turbo:
If that's the case, then how can a red dot be used for SD/HD? If I can't hit a target at 10 feet, because I zeroed at 15 feet, how can I trust this type of optic? I would think the red dot would be fine withing a range of maybe 5ft - 50ft. If a different of 5 ft is enough to be completely off target, I'm just going to stick to iron sights. Originally Posted By mx597turbo:
Originally Posted By dalle0001:
And yes, aiming at something 15 ft away is going to be drastically different than aiming at something 10 ft away. A rifle round is not shooting in a straight line. |
"Those who would give up essential Liberty, to purchase a little temporary Safety, deserve neither Liberty nor Safety." -Benjamin Franklin
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Originally Posted By mx597turbo: If that's the case, then how can a red dot be used for SD/HD? If I can't hit a target at 10 feet, because I zeroed at 15 feet, how can I trust this type of optic? I would think the red dot would be fine withing a range of maybe 5ft - 50ft. If a different of 5 ft is enough to be completely off target, I'm just going to stick to iron sights. All vertical? Or horizontal? |
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Originally Posted By mx597turbo:
Thanks for the info. My issue is that there is a divergence between the laser and the sight/dot at different distances. For example, if I align the sight/dot to the laser at 15 feet, and i point the gun at a wall 10 feet away, the laser and sight/dot are no longer aligned. |
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Originally Posted By mx597turbo:
If that's the case, then how can a red dot be used for SD/HD? If I can't hit a target at 10 feet, because I zeroed at 15 feet, how can I trust this type of optic? I would think the red dot would be fine withing a range of maybe 5ft - 50ft. If a different of 5 ft is enough to be completely off target, I'm just going to stick to iron sights. Originally Posted By mx597turbo:
Originally Posted By dalle0001:
And yes, aiming at something 15 ft away is going to be drastically different than aiming at something 10 ft away. A rifle round is not shooting in a straight line. You need to first do some reading on firearm sights, how they work, and understand that no matter your setup, your bullet will usually only strike your exact point of aim at one or two specific distances. You also need to understand that this is inherent to any sighting system on any firearm (and can be worse or better at close range depending upon specifics) and it isn’t a problem. When zeroed, you’ll never have more than a 2.5”-3” offset anywhere inside your zero distance which shouldn’t mean a missed shot. Lastly, you need to get the gun out, get it zeroed at an appropriate distance, and work on your holdovers at close range. Also, an RDS is plenty useable well outside of your anticipated effective ranges. With a 50/200 zero, you can easily hit a man size target out to a couple hundred yards without having to holdover much, if at all. |
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Originally Posted By mx597turbo: If that's the case, then how can a red dot be used for SD/HD? If I can't hit a target at 10 feet, because I zeroed at 15 feet, how can I trust this type of optic? I would think the red dot would be fine withing a range of maybe 5ft - 50ft. If a different of 5 ft is enough to be completely off target, I'm just going to stick to iron sights. In a SD/HD situation, you aren't trying to hit the x-ring for the 10 point score, versus the 9 or 8 point shot. You are immobilizing a threat. I am going to attempt to simplify what others have stated. Your sighting system is a visual illusion. It is designed to show you where you will hit when used as designed. It doesn't mean that is exactly where the barrel is pointing. It is simply showing you where the round should impact after it has left the barrel and followed the laws of physics. If you shoot at a distance different than where you zero, you are going to get a different result. That is why we actually shoot our guns and learn where our rounds go when we are using sights or optics. |
| The only thing you are doing wrong is not understanding how a firearm works. Review what others have said and shown you. As far as how a red dot can be used for HD, that is no different than how any firearm can be used for HD. TRAIN. Zero your AR at 50 yds then train at short HD distances. Your POI should be about 1.2 inches below the sight at 25 yards and even lower at closer ranges. Train at 3 yrds, 10 yrds, 15 yrds etc....Know where your POI is going to be depending on the CQC ranges of the shot. Visualize what is happening with your rifle and the projectile. The projectile is 2.5-3 inches below the sight as it leaves the barrel so if you shoot a target at 1 yrd your POI will be close to that much lower that the position of the sight whether you use red dot or iron. |
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Originally Posted By jrs93accord: You have to remember that the bullet travels in an arch trajectory. Personally, I zero my red-dots at 50 yards. If I shoot at 25 yards, I lower my POA (point of aim) just slightly. At 50 yards, you should have the same POI at 200 yards. Here is something for you to read. |
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I might be double-posting since this topic was moved.
Though I no longer use them in an AR, I used lasers to get me on paper at 25 meters. Get it dialed in. Then I would take it from there out to 50 meters with optics hard sights. I now stick a target out at 25 the size of a kid's poster board just in case I'm initially that far off. Get it dialed in and go to 50 and do the best I can. I know the characteristics of my box ammunition (my range stuff) and pretty much memorize my poa / poi at distances 50m and in. I then do the same with my more costly SD stuff which surprisingly ain't all that much different regarding poi using the same poa. Actually, not enough to adjust optics if my goal is strictly to disable a threat. With my 100m and greater gun (scoped), I use only my heavier SD stuff. Lastly, I've done this with a cleared weapon to include bcg removed but you should be able to visualize the following: A friend stands at a 50m distance. Your gun is zeroed at 50. As you keep the dot on a spot on the target (friend), have him walk toward you. Your poa remains constant but the poi shifts. Thus, if the friend stopped at 25, you would now see that the poi has dropped approx 1.5" or so. In reality, I've seen any where between a .75" drop to approx 1.5". Aiming at the tip of his nose is now impacting lower lip to upper lip. With all that said, poi will be influenced by the height of you optic above bore centerline, velocity, bullet weight. Other influences like wind and such but those are the 3 basics. This better explains what I'm trying to convey. However, in this case if using a simple red dot, you would compensate (normally) by physically adjusting your poa as compared to the video using mildots. Ranging Adjustments This should be helpful too. AR15 Zeros |
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What you're doing wrong is not realizing bullet trajectory. A laser has no trajectory, so it is useless for the way you're using it. A laser bore sight is made to get you on paper to then start the zeroing process. A bullet rises and falls. This is why the bullet will impact lower or higher at nearly any distance besides the one you zero'd at and its corresponding drop number that matches the zero. (Such as 50 yard/200 yard zero) The bullet rises to 50 and matches your optics point of aim. As the bullet keeps moving it rises above your point of aim, then starts to fall. When it reaches 200 yards then bullet has fallen back down to your 50 yard zero point of aim. I hope this helps. If you're getting horizontal difference, (again- not with the laser- that's nearly useless here) then you have another issue entirely with the gun or optic |
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Originally Posted By MILSPEC556:
What you're doing wrong is not realizing bullet trajectory. A laser has no trajectory, so it is useless for the way you're using it. A laser bore sight is made to get you on paper to then start the zeroing process. A bullet rises and falls. This is why the bullet will impact lower or higher at nearly any distance besides the one you zero'd at and its corresponding drop number that matches the zero. (Such as 50 yard/200 yard zero) The bullet rises to 50 and matches your optics point of aim. As the bullet keeps moving it rises above your point of aim, then starts to fall. When it reaches 200 yards then bullet has fallen back down to your 50 yard zero point of aim. I hope this helps. If you're getting horizontal difference, (again- not with the laser- that's nearly useless here) then you have another issue entirely with the gun or optic 
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IMO, OP's issue is not understanding his SIGHTS, not trajectories. Let's talk about the sights.
The laser beam is a straight line. The red dot presents the equivalent of a straight line (to your eye, the line of sight). The trick is, those two lines intersect at only one point, at only one point, at only one distance. For now, let's call this the zero. At any distance other than the zero, the two will NOT COINCIDE. If you aim at something closer than the zero, the two will not coincide. If you aim at something farther away than the zero, the two will not coincide. If you get closer and closer, the two will get farther and farther apart. If you go longer and longer, the two will get farther and farther apart. All this is normal. |
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OP asked, "can you trust these sights for HD use?"
Yes, without question. Whether the sights are iron sights or red dot or telescopic or whatever, all sight exhibit this behavior and they always have. Between the muzzle and that first ballistic zero, the offset will be no more than the height of the sights above the bore (typically ~2"). If you get a ballistic zero at 50 yards, rest assured your point of impact be only those 2" or less - irrelevant for HD purposes. Beyond the ballistic zero, the deviation can get larger than the sight height. At long ranges it is lot larger. Review Plasticseng's post, above - once zeroed at 50 yards you are never more than 2" off from 0 to 250 yards. This issue is something you will learn to deal with as you gain more experience as a shooter. Shooting well is a skill, something you have to learn and practice. |
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Not a single person in this thread seems to have answered the OP's question-- at all.
The problem that is alarming him has nothing at all to do with trajectory or external ballistics at all. He is getting his initial zero with a lazer, but he's forgetting to account for the height-over bore of the optic. When he zeros with a laser at 10 yards, like he is describing, the red dot's POA should be about 2" above the lazer's POI. (equal to the sight's height over the bore). There used to be printable templates out there for close range preliminary zeroing of various optics at specified distance. The Army used to have a system called AIMSS (something like that?) for prerange laser zeroing that had templates showing where the sights and the laser dot should line up. |
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Originally Posted By FightingHellfish:
Not a single person in this thread seems to have answered the OP's question-- at all. The problem that is alarming him has nothing at all to do with trajectory or external ballistics at all. He is getting his initial zero with a lazer, but he's forgetting to account for the height-over bore of the optic. When he zeros with a laser at 10 yards, like he is describing, the red dot's POA should be about 2" above the lazer's POI. (equal to the sight's height over the bore). There used to be printable templates out there for close range preliminary zeroing of various optics at specified distance. The Army used to have a system called AIMSS (something like that?) for prerange laser zeroing that had templates showing where the sights and the laser dot should line up. "I recently got several Holosun 403R reddot sights for a couple of ARs. I took one to the range for the first time today, and sighted it in. At the particular distance I sighted it (about 10 yards), it worked perfectly. I went to confirm the zero at 20 yards, and it was way off. I zeroed at that distance, and it was fine. When I moved the target closer, it was way off again. I got home and zeroed the scope to a laser bore sight at about 5 yards. Leaving the bore sight in the chamber, I looked through the red dot and aimed around the room. The laser and dot diverged substantially at different distances. I tried my other Holosun (same model), and it exhibited the same behavior. I had both sight mounted near the front of the upper, and the divergence happened with both eyes open, as well as just one eye open. I tried this with my scope (Nikon m223 2-8x), and also got the same divergence. What am I doing wrong. Is there a minimum distance I have to sight the guns at? If so, then how can I rely on the red dot for HD, where the range would be extremely short? Thanks for any info." |
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Originally Posted By mx597turbo:
If that's the case, then how can a red dot be used for SD/HD? If I can't hit a target at 10 feet, because I zeroed at 15 feet, how can I trust this type of optic? I would think the red dot would be fine withing a range of maybe 5ft - 50ft. If a different of 5 ft is enough to be completely off target, I'm just going to stick to iron sights. How much do you actually shoot? |
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Originally Posted By FightingHellfish:
Not a single person in this thread seems to have answered the OP's question-- at all. The problem that is alarming him has nothing at all to do with trajectory or external ballistics at all. He is getting his initial zero with a lazer, but he's forgetting to account for the height-over bore of the optic. When he zeros with a laser at 10 yards, like he is describing, the red dot's POA should be about 2" above the lazer's POI. (equal to the sight's height over the bore). 
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| Just to be sure: you're only talking about divergence in the vertical plane, correct? Is everything still aligned horizontally? I just want to be certain that we haven't overlooked an issue other than failure to account for trajectory and HOB. |
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Originally Posted By webman:
Just to be sure: you're only talking about divergence in the vertical plane, correct? Is everything still aligned horizontally? I just want to be certain that we haven't overlooked an issue other than failure to account for trajectory and HOB. Thanks to everyone who contributed to this thread. As a math teacher, I'm embarrassed I didn't realize the triangle made between the scope, bore, and target. Assuming bullet drop is minimal to 50 yards, I attached a quick sketch of what I was experiencing. 
I am going to use this sheet to zero at the indoor range, then verify at an outdoor location: 50/200 Zero Sheet |
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Originally Posted By mx597turbo:
Yes, the change was only elevation. There was no horizontal change. Thanks to everyone who contributed to this thread. As a math teacher, I'm embarrassed I didn't realize the triangle made between the scope, bore, and target. Assuming bullet drop is minimal to 50 yards, I attached a quick sketch of what I was experiencing. https://i.imgur.com/y70XNym.jpg I am going to use this sheet to zero at the indoor range, then verify at an outdoor location: 50/200 Zero Sheet Originally Posted By mx597turbo:
Originally Posted By webman:
Just to be sure: you're only talking about divergence in the vertical plane, correct? Is everything still aligned horizontally? I just want to be certain that we haven't overlooked an issue other than failure to account for trajectory and HOB. Thanks to everyone who contributed to this thread. As a math teacher, I'm embarrassed I didn't realize the triangle made between the scope, bore, and target. Assuming bullet drop is minimal to 50 yards, I attached a quick sketch of what I was experiencing. https://i.imgur.com/y70XNym.jpg I am going to use this sheet to zero at the indoor range, then verify at an outdoor location: 50/200 Zero Sheet |
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Several people now have identified OPs main problem: his red dot is between 2.5” and 3” above the centerline of the rifle bore. It’s sighting axis and the bore’s axis converge (zero) at only one point. That point changes as the yardage chosen for zero changes. At close range, this radically changes with relatively small changes is zero distance as a matter of simple math.
He needs to zero at longer range, like a 50 yard equivalent. If he does so, he will always be no more than about 2” low or 2-3” high all the way to almost 300 yards. I see he has figured this out. His diagram will help other people understand this unavoidable phenomenon due to out high over bore line of sight. |
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Originally Posted By mx597turbo:
As a math teacher, I'm embarrassed I didn't realize the triangle made between the scope, bore, and target. Want to go farther, extend the learning? Pick a distance for zero. Calculate the offset (the error) between the bore line and the line of sight as you change the distance to the target. Then, using a ruler, measure the error. Compare the measurements to your calculations. Do they agree? Why/why not? Here ends the lesson. 
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In the army they always drilled it into our heads to remember to put the dot ~2" high at very close range to compensate for height over bore, or at least to be cognizant that our shots would be ~2" low. I guess you take it for granted that some of this stuff is common knowledge. |
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Originally Posted By mx597turbo: Yes, the change was only elevation. There was no horizontal change. Thanks to everyone who contributed to this thread. As a math teacher, I'm embarrassed I didn't realize the triangle made between the scope, bore, and target. Assuming bullet drop is minimal to 50 yards, I attached a quick sketch of what I was experiencing. https://i.imgur.com/y70XNym.jpg I am going to use this sheet to zero at the indoor range, then verify at an outdoor location: 50/200 Zero Sheet EDIT: Just looked at your drawing. No doubt you really are a math teacher.
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Originally Posted By mx597turbo: Yes, the change was only elevation. There was no horizontal change. Thanks to everyone who contributed to this thread. As a math teacher, I'm embarrassed I didn't realize the triangle made between the scope, bore, and target. Assuming bullet drop is minimal to 50 yards, I attached a quick sketch of what I was experiencing. https://i.imgur.com/y70XNym.jpg I am going to use this sheet to zero at the indoor range, then verify at an outdoor location: 50/200 Zero Sheet |
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Originally Posted By Daggertt:
In the army they always drilled it into our heads to remember to put the dot ~2" high at very close range to compensate for height over bore, or at least to be cognizant that our shots would be ~2" low. I guess you take it for granted that some of this stuff is common knowledge. |
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