The LMT attachable sight has elevation but the LaRue and the Troy don't, so I'm wondering what the zero would be using these sights. I realize different ammo would give a different zero, and I suppoe rifle twist would matter too. So this is an open question concerning how these sights work as stand alones.

I'm uncertain which sight I'm going to get for my A3 upper. I'm leaning towards the LaRue. This upper is the SDI mid-length 1/7 twist 16" barrel currently offered by Talon Arms. I'll probably be shooting Federal Eagle and Winchester White Box, along with surplus stuff. This will be my first AR.

GL

+++ money order sent for a Bronze membership - cuz I want access to the archive +++

You adjust the height of the front sight to adjust elevation.

I prefer flip sights, so I would get the Troy. YMMV.

Thanks. Shows what I know. I thought the LMT had elevation adjustment, and that was an advantage with it over the LaRue. I've also read both Troy and LaRue reviewers saying "this is a back up sight so elevation is an unnecessary addition."

GL

The zero is adjusted with the front sight post.  The elevation wheel on the rear is for adjusting for range once you have it zeroed.  But the .223 shoots flat enough that if you zero at 50yds you're within about 1.5" of POA out to about 250yds, which is plenty far enough for a backup sight.  Or for a primary sight for most uses.   Unless you're going to shoot 300+ yds often, you won't miss the wheel.

I went with a Troy on my SDI Midlength 1/7.  I like it quite a bit, plus it folds down and out of the way for when my aimpoint is being used.

Like everyone else has said, adjust the front post for elevation.  You can use a bullet tip and leatherman to adjust it, or there is a handy little tool out there that makes it alot quicker and easier.

Thanks everyone. I'm understanding better now. I found a copy of TM 9-1005-249-10, the operator's manual for the M16 and M16A1 that I bought at a gunshow years ago. It shows there that those models had a rear sight with two apertures for range (page 2-16). The unmarked aperture was for targets from 0-300 meters and the aperture marked L was for 300-400 meters. The low light level system on the next page indicates that the apertures of that different system have different functions: one being simply a low light ghost ring style and the other to be used for normal conditions.

So with the standard sights on the M16 and M16A1 you'd switch apertures to the L aperture for targets beyond 300 meters, the L meaning "long". Sighting in would be done, it looks like (page 2-19) using the L aperture for point of aim at 25 meters, which would put the battlesight zero at 375 meters with the L aperture and at 250 meters when using the umarked aperture. Using the unmarked aperture, the trajectory would never rise above 3.5" and would be at point of aim at 250 meters. The bullet would impact below point of aim before 25 meters and even a short distance beyond 25 meters (since it was the L aperture that was used for the 25 meter zero) and also beyond 250 meters. This, of course, with the ammo and twist rate of those models. For the faster twist rates and the new varieties of ammo we're shooting, trajectories would differ.

Okay. So now I'm wondering how the LaRue and Troy dual apertures are set up. Do they follow the purpose of the old A1 standard sights, where you switch apertures for distance, or are they designed like the earlier low light level system mentioned above and on page 2-17 of TM 9-1005-249-10 where one simply allows more light but doesn't change point of aim?

What's got me wondering is Troy's website saying of their folding battle sight: "Dual peep, same plane aperture allows for perfect co-witness of red dot and holographic optics." This sounds to me like the apertures do not affect point of aim but only differ in amount of light allowed. LaRue doesn't go into detail. I've never used peep sights so I realize I may be misunderstanding.

As far as which of the two I'll choose (LaRue or Troy) I'm still leaning towards the LaRue because I don't think I'll be getting an Aimpoint or EOTech, or using a scope, for quite a while, so the rear sight isn't really going to be a Back Up sight, but my Main sight.

GL

+++ That money order for my Bronze membership must not have arrived at AR15.com yet. +++

Troy's apertures are the same height and do not effect point of impact. I have not shot a LaRue BUIS and I do not know which apertures it has.

its a buis
no elevation needed imo

As everyone has said, you zero for elevation with the front post.  I found that when going with the LaRue, I had to get a taller post.  Some folks get by with the std post, but some need to go taller.  

My carbine zeroed with the std post but it was backed almost al the way out to get it to zero.  So much so that you could see daylight between the FSB and the base of the post.  I wasn't comfortable with that so I went with the taller post and it zeroed fine.

Quoted: As everyone has said, you zero for elevation with the front post.  I found that when going with the LaRue, I had to get a taller post.  Some folks get by with the std post, but some need to go taller.   My carbine zeroed with the std post but it was backed almost al the way out to get it to zero.  So much so that you could see daylight between the FSB and the base of the post.  I wasn't comfortable with that so I went with the taller post and it zeroed fine.

Thats cause you didn't buy a Colt!