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Posted: 2/4/2008 4:08:15 AM EDT
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Just curious. If you have an Aimpoint in a mount that puts your BUIS in the lower 1/3 (standard FSB) and you zero the irons and optic both at 50 yards, should or will the two line up? Will the dot sit on the tip of the front sight when you look through the iron sights? I'm not talking about zeroing one and bringing the other to it, I mean zero them both seperately at the same distance. My thought is no since the optic is sitting higher it changes things I guess. |
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I don't get it. I thought lower 1/3 co witness was so you can have the dot floating a little bit above the front post. In case you want to see under it. Then, when sighting on the red dot, you should be looking over your rear ap, not through it. Absolute co witness would be with the dot right on top of your post or even half dot on the post itself while looking through your rear ap, with your irons lined up. Seems to me, nobody has made this point yet. Isn't that the original question? So my answer is NO, it shouldn't be on top of your post, if you have a lower 1/3 co witness. It should be a little above it so you don't have to look right through your rear ap and have the irons line up. You should be a little above that. That's how I understand it. I don't have one though. My brother has an absolute cowitness, for the most part, with his aimpoint. |
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The RED dot sits on top of FRONT SIGHT POST With my LARUE CANTILEVER/ML2 I JUST SEE THE FRONT POST AND EARS OF THE FSB My BUIS is zero at 50yards as well as my ML2 aimpoint! SO RED DOT HAS SAME ZERO WICH SITS ON THE POST CENTER COW WITT LIKE ON MY OLD BUSHMASTER with QRP and ML2 YOU SEE A BIT MORE OF THE FRONT SIGHT! I HAVE BOTH TYPES SO IM NOT GUESSING Factory LMT Defender 2000 with LARUE CANTILEVER/ML2 and arms 40Lsp LMT M4 with 551 Eotech and arms 40 Bushmaster QRP arms 39/Aimpoint ML2 |
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If both the dot and irons are sighted in at the same distance, the dot will sit on top of the front sight post whether you have an absolute or a lower 1/3 cowitness. The aimpoint doesn't care if your eye is in the center of the tube or not, the dot will still be on target. What is good about lower 1/3 is you don't have as much iron sight clutter in the veiwing window of the optic, but you can still use the irons through the optic. I'm with FMJ, a lower 1/3 setup is not that great when using irons. However, if the optic is the primary sighting device, then it should be the easiest to access and that is what a lower 1/3 cowitness does. edited to add: To the original question.......If you zero each seperately, when you look through the irons the dot should sit on top or split the top of the front sight post. If they don't, then they are not sighted in at the same distance. |
THANK YOU Some guys rather guess than just say I really dont know 
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hope this help ya out some |
I think this is incorrect or at least ambiguously worded. If the dot and the irons are zeroed at the same distance, and are in the same plane like on an absolute cowitness then when using irons or dot, the dot will be in the CENTER of the optic and will be on the top of the front sight post. If the rear buis was flipped up, your eye would be looking through the rear aperture, with the dot sitting on top of the front sight post - all perfectly lined up. If using a lower 1/3 cowitness (by adding a 0.3" riser to the optic for example), with the dot and irons zeroed at the same distance, things can be different. The riser allows the viewer to look through the CENTER of the optic, ABOVE the sight plane of the irons. To do so, your cheek weld must compensate by raising roughly 0.3" and your line of sight will be 0.3" higher above the rail. You can no longer be sighting through the rear buis aperture (if it was in the up position) because, like I said, your line of sight is roughly 0.3" above the plane of the irons. It's a little more confusing because if you drop your cheekweld roughly 0.3" and look THROUGH the rear aperture to look at the front sight, the dot will now be on the top of the front sight post. What has changed is the dot will NOT be centered in the optic, but will be LOW in the optic. Just as caw375 stated, "The aimpoint doesn't care if your eye is in the center of the tube or not, the dot will still be on target." The riser simply allows you to have a 1/3 cowitness and look through the center of the optic and focus on the dot without the clutter of the irons in the way. if the optic fails, just drop your cheekweld a bit and you can use the irons. |
Thank you. That's what I was trying to say but came across wrong I guess. I didn't see the point of sighting through your irons if you have a lower 1/3, less things to skew your sight picture. That's the whole point, to be able to look over the rear ap, unless your optic goes down. Then they are very, very short distance away and still there. At least that's what I thought. I don't have one set up this way though. |
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AGAIN I KNOW NOT THINK I OWN these M4`s Bought my First in 1983 LARUE CANTI GIVES 1/3 COWITT BUIS zero at 50 yards Aimpoint zero at 50 yards Mount is LARUE CANTILEVER RED DOT SITS ON TOP OF POST OF FSB VERY SIMPLE NOW My EOTECH ON LMT M4 EOTECH 551 zero at 50yards ARMS BUIS ZERO AT 50 yards RED DOT SITS ON TOP OF FRONT SIGHT POST AND GIVES A CENTER COWITT A LARUE CANTILVER only moves the aimpoint up a tad So you dont see all the FSB THEY HAVE THE SAME ZERO WHY WOULD THE RED DOT BE OFF FROM THE FRONT SIGHT POST |
YES ! BOTH ARE RIGHT BUIS zero at 50 yards Aimpoint zero at 50 yards with QRP the dot will be on the front sight post CENTER COWWITT BUIS zero at 50yards aimpoint with 1/3 Larue canti zero at 50 yards red dot sits on post this is 1/3 cowitt Its the CENTER WINDOW PART THATS GETTING MIXED UP |
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FMJ. Do you ever look over your rear AP with your lower 1/3 mount? What would be the point of a lower 1/3 if the dot didn't go above your front post at all? You're saying the only difference is now you have a dot lower in the scope and less of your FSB in the picture. But the dot still sits on top of your post. I'm assuming that's when you are looking through your irons. But again, if you raise your head up over the rear ap, does it change anything? Maybe it keeps the dot still on top of the post and just moves it into the middle of the scope. Is that correct? I'm not trying to say you're wrong. I'm trying to understand. What's the point of a lower 1/3 if you're still aiming through the irons all the time? This is Harv's post in another thread: Bradd_D Lower 1/3 since my primary sighting device is an Aimpoint and I prefer the less restricted FOV. There's my answer.... All I want to see.. is a big ole 4 MOA Dot of Death....I f I wanted to see my Irons all the time.. I would just take off my Aimpoint and use them... This is where I'm getting my thoughts, seeins as I don't have one. |
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NO!!!! I shoot NOSE TO CHARGE HANDLE WITH THE LMT M4 DEFENDER with Larue canti/ML2/ARMS 40Lsp When I bought my Fisrt Aimpoint XD with 3moa I used a QRP/Arms 39 & A1 Bushmaster 14.7 Still shoot nose to CH (A1 is a Fixed sight )LMT M4 with 551 eotech /arms 40 I shoot NOSE TO CHARGE HANDLE I shoot with my BUIS up The A1 is already up WHY a Larue cantilever on a 14.5 LMT M4 Defender 2000 I LIKE MY AIMPOINT FURTHER AWAY from BUIS When I bought it Had no Idea it was 1/3 cow witt Since I shoot more with BUIS I might of not bought the Larue cantilever But it does hold a ZERO after takeing On/off DOES THIS HELP BTW CENTER COWITT ON MY EOTECH DOESNT BLOCK ANY VIEW WHEN I SHOOT TRY BOTH OUT FOR YOUR SELF! A 50 yard zero BUIS 50 yards zero aimpoint RED DOT IS SITTING ON THE FRONT SIGHT POST SAME PLANE Man Thats HOW In zero my AIMPOINT/EOTECH by putting dot on Post of FSB after it was zero at 50Y as Taught by CHUCK SANTOSE Chuck Santose is the nice guy who Help me get going with Aimpoint back Years ago |
This part is what y'all are skipping. If you look over the irons and just look at the dot (which is what I do under normal situations) the dot will be above the front sight. Some people think the dot will sit at a different position on the front sight post when viewing rear sight, dot, and front sight all at the same time when it is an absolute or lower 1/3 position. With an absolute cowitness half of the optics viewing window will be taken up by iron sight clutter when looking over the irons. Does this really matter with a 1x, both eye open, red blob dot?.....NO. BUT, a lower 1/3 will give you LESS CLUTTER, an almost full optics tube view, and a little more heads up posture. Why is a lower 1/3 not great when using irons?.......For me it is because the bottom of the large aperture gets lost in MY vision with the bottom of the aimpoint tube. SO WHAT, the aimpoint is the primary sighting device, and the irons are still very usable. WHY would you even use the irons?.......When your aimpoint washes out and you don't have time to turn it up, when batteries die(right), to line everything up perfect for a long winded shot, to make sure everything is still lined up after you drop your rifle. It is simpler than all of this big talk, but is misunderstood. It is pure preference. |
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How about this. Dont use the friggin iron sight unless you need to. You are not supposed to use both irons and the red dot at the same time. That is why they have the nifty little feature that allows them to fold down, and out of the way. PRIMARY = Optic BACK UP/SECONDARY= Irons Of course most people have fixed FSB's so you are always going to have that in your field of view but if you are focusing properly (on your target) it will be blurry. Fold down that rear fucker and you will have a much better field of few for detecting movement/threats, aiming, et cetera. When you have all 3 sights going you are doing nothing but hindering yourself. As far as 1/3 lower cowitness your red dot is going to sit a bit above the front sight post (fsp). If you have the dot somehow sitting RIGHT on top of the fsp you're doing it wrong. Putting the dot on the FSP lets you know when are looking directly through the optic with no side to side or up and down movement off center. Its good for establing feel as to where to put your head on the stock, and with enough practice you will develop muscle memory. If your irons are zero'd you can also use them to rough zero the optic. With that said trying to shoot by putting the dot on top of the front sight post or aligning it somehow is a waste of time and making you a slower shooter. These optics have a nifty thing, too, and are almost 100% parallax free. What that means is it doesnt matter what angle you look through the sight; as long as you can see the dot that is where the bullet is going to hit. You dont need to align anything but the dot and target (NO IRONS!). This is why cowitness is a bunch of bullshit and a marketing gimmick. Fold down those irons and blast away. You'll find you have a much better field of view, target aquisition is quicker, shot on target is quicker, and is generally much much better. There is a reason for the acronym BUIS. BACK UP iron sight. That doesnt mean its half your primary sight. Its a back up system if your optic fails. If you find yourself out of battery power in a fire fight, it gets hit by a round, whatever, either take it off (you do have QD levers right?) or leave it in place if you can still see through, flip those fuckers back up, and keep shooting. Once you have a minute take the sight off or leave it on if its not obvious and try to see why its malfunctioning. Replace the battery (you do carry a spare battery or two or three right?) and check for function. If its GTG slap that fucker back on, and flip down those irons again. Otherwise put it in a pocket until you are back from your mission, and keep using your back ups. ETA: This is just my opinion. You can read a much better version written by Pat Rogers in the DEC SWAT mag. He explains it perfectly. And a 200M zero is much better. It allows for much less "error" between the distance between your optic and barrel. If you zero at 50M your rounds are going to be striking high at 200+ meters.... Your line of sight is like a laser (straight) but the bullet is arching. You want that laser to be right in the middle of the arch of the bullet from the muzzle to about 300m. A 200M zero is about the best of achieving a medium between a long distance zero and a CQB zero. |
I AGREEE IF ONE STUCK HIS HEAD UP AND SHOOT THE RED DOT WOULD APPEAR WELL OVER THE POST!!! I SHOOT NTCH SO THE DOT IS ON THE POST IRONS ARE ZERO AT 50YARDS YOU PUT THE RED DOT ON THE POST THEN FINE ADJUST IT AT THE 50Y EASY Ive done this since 2001 TAUGHT BY CHUCK SANTOSE YOU KNOW THE 50 yard Zero man himself I think Chuck Knows WAY MORE THAN YOU |
LMT BUIS Larue BUIS they dont fold!!!  I shoot with my BUIS up most all the time Im at the range I shoot mostly IRONS NTCH AT ALL TIMES and some of the time aimpoint/eotech A1 bushmaster QRP/ARMS gooseneck/Aimpoint 3moa dot How do I fold my sight down Since Ive been shooting over 35+ years now I think I will stick with what I KNOW WISH CHUCK SANTOSE WAS HERE 50yard BUIS 50 yard AIMPOINT DOT SITS ON THE POST Both have the same POI NTCH IS THE WAY I SHOOT SO THERE YOU GO  IVE BEEN HERE SINCE 2001 and Ive pick up little bit now IM DONE WITH THIS OVER AND OUT |
Whatever works for you.... |
| lol you guys are funny. look through the red dot straight, now move your head left right up down, what happens???? the dot moves to stay on target, so looking straight through, the dot will be ABOVE the front iron site now move you head down to look through the iron sites and the dot drops. thats the whole point of 1/3 witness is to change the angle on your site to move the iron site out of the way for a better veiw. so yes the sites hit the same spot but are at different angles. No one told me I LOOKED |
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