View Full Version : Weird Aimpoint T1 phenomenon
I apologize in advance for what must seem like a newbie question.
I have two genuine Aimpoint T1's. They are not really close in serial numbers, so reducing the possibility of manufacturing defects in the same production lot. They were purchased a few years ago from Botach (I know, but I never had problems with them). They are both mounted on separate FN FS2000s with Larue QD low mounts. The optics are positioned as far forward on the rail as possible. In fact, they are right behind the front sight wings.
They both have the same problem, they will NOT co-witness. The iron sights are in the lower third of the T1. This is lowest QD mount that allows any possible co-witness.
My procedure is: I FIRST sight in the weapons at 50 yards with no optics . . . only iron BUIS (Mounted correctly, so they are not the variable). Nice repeatable groups.
SECOND, I attach the T1 via Larue mount to the rail (T1 to Larue mount attached correctly and blue thread locked). BUIS are folded out of the way. I sight in the red dot at the same target at 50 yards. Again, nice repeatable groups.
When done, I flip up the rear BUIS and shoulder the rifle. The red dot is NOT on top NOR centered over the front iron sight. The dot is low, entirely below the horizontal top edge of the front sight post and off to the right, slightly overlapping the right edge of the post.
I hope I can illustrate what I see:
_
l l*
l l
l l
The asterisk represents the red dot as viewed through the BUIS on both T1's.
It should be like this:
*
l l
l l
l l
I thought it very odd as every co-witness pic I have seen shows the red dot sitting centered on the top of the front sight. As I do not shoot with the BUIS raised, it has not been a concern all this time. I figured I would QD the optic if it ever went tits up and then flip up the BUIS. But this doesn't seem ideal.
After everything was sighted in as detailed above, I decided to get cute and mess with it. I adjusted the elevation and windage of the red dot so it did co-witness, centered on top of the front iron sight. This time....a nice group appeared approx. 1.5" low and right. Crap!
In other words, my BUIS are shooting to different points of impact depending whether I sight in with the BUIS alone compared to sighting in the BUIS while looking through the T1. This is with two different rifles with identical set ups.
It does this with different ammo (55gr, 62gr, 75gr). I have decent vision and do not wear eyeglasses, though I may be ever slightly far-sighted.
Am I reversing the co-witness procedure? For example, is the proper procedure to first mount the T1 on the rail and then sight in both iron BUIS and red dot? If this is the case, I would think the optic cannot be detached as the optic's distortion is required to accurately shoot your BUIS. What happens if the glass cracked or fogged to the point you have to detach the T1?
Is it due to the extreme forward mounting? Is it my eyes?
skew handguard and as such the front sight?
I am not following at all. Which mount do you have? Larue absolute co-witness, lower 1/3 co-witness or the short?
I am not following at all. Which mount do you have? Larue absolute co-witness, lower 1/3 co-witness or the short?
My English composition-fu is weak. I edited my original post in an attempt to clarify.
You're overthinking it a bit. As long as you are on target with the irons by themselves, and with the Micro by itself, then you are good to go. Whether or not the dot lollipops on the front sight is irrelevant. The dot shouldn't interact with the irons other than that initial rough cowitness to get you on paper, but that's just a starting point. You have to fold the irons down and zero it properly from there.
They both have the same problem, they will NOT co-witness. The iron sights are in the lower third of the T1. This is lowest QD mount that allows any possible co-witness.
If you're using a lower 1/3 co-witness, they will not likely align. If you're dialed in with your optic by itself, and with your irons by themselves, you're good to go.
dmaxfireman
11-01-13, 08:31
You're overthinking it a bit. As long as you are on target with the irons by themselves, and with the Micro by itself, then you are good to go. Whether or not the dot lollipops on the front sight is irrelevant. The dot shouldn't interact with the irons other than that initial rough cowitness to get you on paper, but that's just a starting point. You have to fold the irons down and zero it properly from there.
Gotta disagree with this, you should be lined up vertically. Horizontally is all dependent on the zero distance
.
My first guess is that there is a inconsistent cheek weld. If you were to use your BUIS and red dot at the same time which has the more centered group.
DreadPirateMoyer
11-01-13, 08:53
I believe you're using an absolute cowitness, not a lower 1/3rd?
And on that note, I've never had an Aimpoint and BUIS line up perfectly when individually zeroed, and I also use absolute cowitness mounts.
Is your rear sight zeroed to the right? I've noticed that the dot often tracks to the right or left on the front sight post respective to the right or left adjustment on the rear sight.
This has always bothered me, but I've confirmed zero with my sights multiple times, so I think it's fine. It makes sense to me, at least from an engineering perspective, because unless the sights are PRECISELY mounted on the same vertical and horizontal plane (which is almost impossible), I can't see their sight picture/zero lining up perfectly anyway. I'm honestly not sure if that's even possible.
Gotta disagree with this, you should be lined up vertically. Horizontally is all dependent on the zero distance
.
What difference does it make?
If my irons hit POA/POI at my chosen zero distance, then they're good to go.
Likewise if my red dot hits POA/POI at my chosen zero distance, it is good to go as well.
Why mess with it past that?
Doc Safari
11-01-13, 09:07
OP: I have trouble getting ANYTHING to "lollipop" with ANY Aimpoint T1, H1, or R1 (tried all three), except for the LaRue LT103 mount and/or the LMT M16A2 style rear sight. Yes, it's important to me for the red dot to rest on the front sight post, and since it's my rifle, that's how I'm going to have it. :D
People tell me it's "just me" the way I hold my head or something (technique ain't my strong suit).
To make a long story short: try a different BUIS and you may find the problem solves itself.
It became such an aggravation to me that I use a folding rear sight now and keep it in the "down" position.
What difference does it make?
If my irons hit POA/POI at my chosen zero distance, then they're good to go.
Likewise if my red dot hits POA/POI at my chosen zero distance, it is good to go as well.
Why mess with it past that?
THIS!
When did co-witness become defined as the red dot riding atop the front sight post.
Just make sure the sights are usable through the red dot sight and your set.
Sent from my SCH-I535 using Tapatalk 2
dmaxfireman
11-01-13, 09:14
What difference does it make?
If my irons hit POA/POI at my chosen zero distance, then they're good to go.
Likewise if my red dot hits POA/POI at my chosen zero distance, it is good to go as well.
Why mess with it past that?
Not disputing that if it works separately and he is happy then leave it alone.
But if he views the dot through the rear aperture, would be interesting to see which is dialed in. So with the red dot and rear sight both in play, shoot a group off the front sight post and group off the dot. Which is on target and which is off.
What difference does it make?
If my irons hit POA/POI at my chosen zero distance, then they're good to go.
Likewise if my red dot hits POA/POI at my chosen zero distance, it is good to go as well.
Why mess with it past that?
Because it helps to have the dot centered on the front sight post and be able to confim zero just by flipping up the BUIS and seeing if they line up...perhaps after bumping your red dot for example...and I'm talking about AFTER they have both been confirmed for POA/POI.
Yes this can still be done if the dot is off center so long as you remember exactly where the dot is supposed to be in the sight picture, but depending on where it is, it may be harder to do so vs. it being centered.
That said, I've never had a problem with my M3 and PRO lining up on the front sight post. I would tend to agree that it has something to do with an inconsistent cheek weld...but that's hard to diagnose from behind a keyboard.
dmaxfireman
11-01-13, 09:28
Just went into my safe and verified my t1 and m4s both line up nicely with the irons.
First, the idea that your dot (presuming that you're zeroing POA/POI at the same distance on both Irons and RDS) MUST rest atop your front sight post is false.
I've got an H1 on an LT751, stuck on a Noveske 14.5" gun. If I get sight alignment/picture with the irons, my dot's low and right, almost exactly like your first illustration. Irons and RDS are zeroed exactly the same and print the same, so you'd have to pay me to care less about how it LOOKS, because I'd be willing to bet my eyeteeth that all it means is that my FF forend isn't quite perfectly true, which puts my front BUIS just a skosh out of plane with the optic. NOT substantive, as the gun shoots straight, and only one way among many that could explain a dot being somewhere besides the front sight post, yet the gun STILL being correctly co-witnessed.
Anybody thinking "I've never seen it NOT line up....," that's almost certainly completely factual: You've never SEEN it. One's experience isn't invalid....it's the conclusion that's jacked-up.
Second, we're talking about non-AR-pattern guns, here. That's gonna become important in a moment....
Third, even if the desired endstate was to achieve a certain cosmetic goal...which it's not..., you're assuming that the mount you're using is meant to provide the cosmetic condition you wish in the first place. You said you're using the Micro low mount variant. From the LaRue product description of the LT661 (emphasis mine):
Short Shotgun, PS90 & AK (LT661)
QD Mount for Aimpoint Micro Sight. Gets the Micro down low to use on Shotguns, PS90's and AK's
No mention of co-witness, at all. Only that it mounts a Micro lower on a rail than the 660 and 660HK (each of which identify both type of guns and type of co-witness, because each of which is designed to provide for it).
Heed The Rat.
I don't know if this is what is happening, but here's a theory....
If you happen to have astigmatism, you could be zeroing the red dot based on the apparent (distorted because of your vision) center of the dot...
Looking through a peephole such as a rear sight has the effect of "correcting" astigmatism for things like a dot sight.
So if you have astigmatism you may be effectively seeing different dots depending on whether or not you are viewing through the rear sight, which could explain why you don't get the "lollipop".
because I'd be willing to bet my eyeteeth that all it means is that my FF forend isn't quite perfectly true, which puts my front BUIS just a skosh out of plane with the optic. NOT substantive, as the gun shoots straight, and only one way among many that could explain a dot being somewhere besides the front sight post, yet the gun STILL being correctly co-witnessed.
Anybody thinking "I've never seen it NOT line up....," that's almost certainly completely factual: You've never SEEN it. One's experience isn't invalid....it's the conclusion that's jacked-up.
This made me realize that I've always used a VIS upper, so it would make sense for mine to always line up. I'm about to go zero my MUR/NSR that just replaced my VIS and may very well see this happen. Like I said above though, it will still work.
Has anyone even looked at the gun he is having this problem?? I have no idea how tall or short his irons are. He isn't having problems with an M4! GH
Failure2Stop
11-01-13, 10:36
Far more often the dot does not perfectly sit atop the front sight post than does, in my experience and observation of a few thousand setups.
Also, since you zeroed your irons without the glass of the T1 between the sights, once you put it there you induced some degree of parallax.
I believe that both systems SHOULD be zeroed independently, as in the event of an optic failure you might need to ditch the optic and rely on the "pure" iron zero. Of course, checking POI shift through the glass with the dot off is pretty important as well.
Far more often the dot does not perfectly sit atop the front sight post than does, in my experience and observation of a few thousand setups.
Also, since you zeroed your irons without the glass of the T1 between the sights, once you put it there you induced some degree of parallax.
I believe that both systems SHOULD be zeroed independently, as in the event of an optic failure you might need to ditch the optic and rely on the "pure" iron zero. Of course, checking POI shift through the glass with the dot off is pretty important as well.
Do you think the parallax is enough to worry about, given that most shooters/setups with a RDS will be about 3MOA? My thought is that it wouldn't be, but you would know better.
Ah.. wow.. irons and red dot clearly not in the same plane/s. Next question.
"exact" co-witness on an AR.. 1.5" mount matching sight heights
"lower 1/3" co-witness.. mount higher
whatever vertical and horizontal offset is involved with unknown aimpoint mount and sights on afore mentioned FN2000... who knows?
Ironman, admittedly unlikely, but also not outside the realm of possibility. Such devices are only as parallax-free as they can be made to be.
Has anyone even looked at the gun he is having this problem?? I have no idea how tall or short his irons are. He isn't having problems with an M4! GH
Yep, that was my 2nd point, of three.
We're somewhat off the edge of the map because it's a completely different gun than an AR configuration, so there may be an element of trying to shoehorn facts to fit a conclusion, instead of using facts to derive one.
G19A3
I'm running a Daniel defense V1 with a Micro t-1 and I have the exact same problem. I've zeroed both independently. But when it comes to lower third witnessing it's just like you said the red dot to the top right. And the mount I'm using is the DD micro t1 mount. I'm gonna try to cowitness zero again this week - we'll see it'll be the fifth time I've tried.
I am wondering if it's cheek weld. Or if I'm getting lazy at some point in the process. But last time I had two army buddies helping me and still it's off to the right. So.....?
Chairborne Stranger
Just went into my safe and verified my t1 and m4s both line up nicely with the irons.
Did you zero the irons and THEN mount your RDS and mechanically zero the red dot aiming point to "match" to your irons without firing live rounds?
OR did you zero the irons and THEN mount your RDS and independently fire live rounds to zero the red dot aiming point independent of the irons?
G19A3
I'm running a Daniel defense V1 with a Micro t-1 and I have the exact same problem. I've zeroed both independently. But when it comes to lower third witnessing it's just like you said the red dot to the top right. And the mount I'm using is the DD micro t1 mount. I'm gonna try to cowitness zero again this week - we'll see it'll be the fifth time I've tried.
I am wondering if it's cheek weld. Or if I'm getting lazy at some point in the process. But last time I had two army buddies helping me and still it's off to the right. So.....?
Any updates Chairborne Stranger?
The dot and sight post aren't gonna line up most times if you truly zero them independently. Simple fact is what you see thru the red dot is different than what you see thru irons/aperture. Lining up a single dot is different than having to align two sights to a target. This is one of the reasons I can sight in a rifles irons then the next guy shoot it and it not be perfectly zero'd. Different people align differently. The mechanical zero of the rifle may be the same but different peoples view thru the sight or optic is different.
I have the micro mounted. Turned it off. Zeroed irons. Then zeroes red dot. Then went back to look though irons to see red dot for true cowitness and it was off to the low right - the red dot. My issue is that this never an issue with my army issue rifle from my arms room. That how we do it. Irons, redd to, then both together.
I haven't gotten back to a range. Hopefully going next weekend bf some buddies redeploy.
I have the micro mounted. Turned it off. Zeroed irons. Then zeroes red dot. Then went back to look though irons to see red dot for true cowitness and it was off to the low right - the red dot. My issue is that this never an issue with my army issue rifle from my arms room. That how we do it. Irons, redd to, then both together.
I haven't gotten back to a range. Hopefully going next weekend bf some buddies redeploy.
The problem is almost everyone has a different answer on how they zero. Some mount the RDS assembly, then zero both RDS & irons SEPARATELY. The irons being sighted through the RDS (red dot turned on/off/whatever).
Independent zero to me means....Zero irons with NO RDS mounted at all. My reasoning is if the RDS goes tits up (failed batt/broken lens/muddied lens/etc.), I use the Quick Detach feature on the mount and take the whole RDS assembly off and now use the irons exclusively (ala regular A2 fixed sights). The irons should be POA/POI because that was how they were zero'd. Now, I fold down the BUIS and mount the RDS assembly. Zero RDS assembly with NO iron sight in view. Upon completion, flip up BUIS. Shoulder the rifle and the red dot is NOT sitting centered nor on top of the front sight post.
Why would I use irons THROUGH a failed RDS? (ONLY if there was no time to QD)
Why would I use irons THROUGH a functioning RDS?
I think my conclusion is viewing the zero'd irons THROUGH two 'imperfect "non-Hubble quality" glass' pieces of the RDS creates a "refracted" iron sight picture. Is this issue called parallax? I dunno.
I also think (as viewed with rifle shouldered) the further the irons are from the circular center of the RDS (i.e. lower third co-witness) the worst it gets. In other words, if an absolute straight line can be drawn from the center of the rear sight aperture....thru the center of the RDS (both pieces of glass)....thru to the top center of the iron front sight post, this offset phenomenon would be minimized, but not entirely gone.(?) **** if I know as all my mounts are lower third co-witness and all have the same phenomenon. Including my four AR's with RDS mounted as far forward on the upper receiver proper. When my ARs are shouldered, the actual position of the RDS is a lot closer to my eye (referenced to the rifle lenghtwise) than the waaay forward mounting setup I have on my FS2000's. Yet the phenomenon occurs the same with AR's and FS2000's.
Like I said **** if I know. That's why I figured I would ask here. Either way, I'm only off 1.5" high left at 50yds, if I have no time to QD and need to shoot through the RDS.
The reason I find it perplexing is that after many years shooting and zeroing and doing range time with my army issue colt - if I go through the exact same steps we use in the army my crap doesn't line up. Never have this issue with my work gun.
Also, we don't really use quick detach stuff. In fact we tie everything on our weapons down with gutted 550 cord. The way is was put to me by a tier one teacher is that often even when the glass breaks on an aim point the red dot still works. And if that fails you can just aim through the busted glass etc. Now Paul Howe I think has a different take on that since in the first moments of the gothic serpent operation his optic was broken and he couldn't get it off which I think I remember hearing him say was a problem.
How is the FSB mounted? I may be off here, but if the FSB is off to either side due to the barrel being slightly rotated, won't this result in what is being described by the OP?
I think I had the same thing going on with an upper that I used to have. My FSB was far enough to the left that my rear sight was ~1/8" left of center.
davidjinks
01-22-14, 13:49
Did I miss it somewhere in this thread……But are the sights hitting to zero and is the aimpoint hitting to zero?
Is the only problem here the sights don't line up?
If the irons get zeroed and they hold zero, the aimpoint gets zeroed and holds zero…Where's the issue?
WickedWillis
01-22-14, 14:01
Did I miss it somewhere in this thread……But are the sights hitting to zero and is the aimpoint hitting to zero?
Is the only problem here the sights don't line up?
If the irons get zeroed and they hold zero, the aimpoint gets zeroed and holds zero…Where's the issue?
Yeah this is where I am scratching my head here as well.
Did I miss it somewhere in this thread……But are the sights hitting to zero (Yes, WITHOUT Aimpoint mounted anywhere on the rail) and is the aimpoint hitting to zero?(Yes, independently)
Is the only problem here the sights don't line up? (Yes, more or less, that is the issue. AFTER irons zeroed WITHOUT Aimpoint mounted, THEN mount Aimpoint. Iron does not cowitness exactly.)
If the irons get zeroed and they hold zero, the aimpoint gets zeroed and holds zero…Where's the issue? (Some zero both while BOTH are mounted. What if they NEED to QD the Aimpoint? Their irons will be off zero.)
Yes, more or less, that is the issue.
davidjinks
01-22-14, 17:10
Maybe I'm still not tracking…
You zeroed your iron sights, correct? When you shoot with your iron sights the bullet impacts at POA right?
You zeroed your aimpoint, correct? When you shoot with your aimpoint the bullet impacts at POA right?
When you put everything together on the rifle and shoot it, the bullet impacts POA right?
So this is just an aesthetics issue right?
The last part of your reply is confusing. I zero my irons while my T1 is in place. I confirm the zero of my irons with the T1 in place and with the T1 detached from the upper. Out to 100 yards I've never had any noticeable shit in POA/POI.
Yes, more or less, that is the issue.
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