6920LE
LT Cantilever mount
Aimpoint M3
LT Troy BUIS
Ammo: tried both 55gr Federal and 55gr Monarch
I was trying to Zero my Aimpoint M3 and also my LT Troy BUIS.
After shooting with just the LT Troy BUIS my shots were shooting low. I’d say 3"+ at 25yrds.
I said the heck with it I’ll strap on my Aimpoint and see what happens. Same result was shooting low.
After Zeroing the Aimpoint to hit Dead on, this was the result:
Is there a problem with my Colt shooting low? I know the BUIS is supposed to be at a proper height already because simply you can not adjust height on it. 2nd Aimpoints should already come zeroed. I’m wondering if there is something wrong with the 6920LE to shoot so low. It almost seems maybe the LT Troy BUIS is to short.
No i did not touch the Front sight post. Thinking it was a 6920 i thought it was most likely seated properly in the first place. Also thats a huge adjustment. I mean the dot is practically sitting in the middle of the front sight post. I doubt it will let you screw it in that deep into the FSB. Maybe the Cantilever mount could of been manufactured to high? I am trying to go for a 1/3 cowitness.
You may want to read thru it to understand the relationship with the front sight post. You need to make an adjustment to it in order to zero at 25 yards.
That site talks about bringing down your POA. But I need to bring up my POA. I’m shooting to low. with BUIS. I don’t believe I can screw my Front sight post into the FSB that low to zero it.
Try it, you’ll likely be surprised. You did read #7 correct? You have no other parts on the rifle that give you elevation adjustment. Just the front sight post, which must be adjusted in order for you to zero your irons at 25 yds.
Generally a 25 yd zero is recommended against. POA/POI at 25 is very limited in use- the organizations that use a 25 yds zero are generally using the rear sight set at 6/3 +2 (for M4s IIRC) which they dial back down to 6/3 once zeroed. This is not applicable for you since you are using the Troy rear.
I only use 25 yds for initial correction and then move onto 50 yards or 200 yards, depending on range constrictions.
At 25 yds POI should be roughly 1" below POA.
Once that is achieved you will be ready for 50 or 200 yd refinement.
I generally prefer to zero the irons first with the dot turned off. Then adjust the dot so it sits at the tip of the front sight and confirm by shooting with the dot centered in the optic.
First, zero the Aimpoint. Don’t worry about where the irons are. Remove the BUIS if you want to.
Next, turn Aimpoint off and zero the irons. Make windage adjustments using the windage on the rear BUIS, make elevation adjustments using the front sight post.
The LT mount should allow 1/3 cowitness. When you are done you should find that with a normal cheekweld, the Aimpoint dot is centered in the glass and the irons are well below the dot, in the lower third of the glass. To use the irons at this point you’ll need to adjust your cheekweld. When you do you ought to see the dot right on top of the FSP, but it will still be in the lower third of the glass.
This is what I was trying to do but the Dot appeared half way down the Front sight post. and that was at 25yards. If i go for 50yards most likely the dot will be even lower on the front sight post. maybe almost sitting on the front sight base.
Uh, that would indicate that you need to move your POI up about 2" - about 6 to 8 clicks on the front sight post (which will drive your front sight down).
The close range you zeroed your Aimpoint along with an unzeroed iron system has made the discrepancy seem larger than it really is.
Yes, you are about 6 to 8 clicks low (edited above, brain fart due to 25 yd distance). Work off of the little detents in the front sight, but it will be roughly 1 and 1/2 to 2 full rotations.
Don’t forget to rezero the Aimpoint as well.
If possible confirm zero at 50 (min) or 200 yards (preferred).
I’m running the exact same set up, 6920, ML3 on a LaRue cant mount, and a Troy battle rear.
Although I have not tried to zero for 25, I had no problem with a 50 yard zero.
Haven’t had an Aimpoint come zeroed out of a box yet. They are close, but not right on.
Failure2Stop said;
I generally prefer to zero the irons first with the dot turned off. Then adjust the dot so it sits at the tip of the front sight and confirm by shooting with the dot centered in the optic.
Yep, what he said…I find it easier to zero the dot.
You should be 1 1/4"-1 3/8" low at 25 yards for a 50 yard zero.
The only thing I’d add is if the Aimpoint is currently zeroed, leave it alone. You zero the Aimpoint independently of the irons.
When you get around to zeroing the irons, turn the Aimpoint off. And I would use the small aperture when zeroing.
You should find that when the irons are zeroed with a proper sight picture, that post and aperture will be in the lower third of the Aimpoint’s window. And when transitioning from one sighting system to the other, you’ll have to make a minute cheekweld shift.
- about 6 to 8 clicks on the front sight post (which will drive your front sight down).