So I have an 11.5" "Sorta 733 build" with a fixed A2 carry handle, carbine gas system, non-F marked front sight base, with 0-800m A2 rear sights shooting 55gr. M193.

Now I know that the elevation adjustments on the 800m A2 sights are designed to work with 62gr ammo from a 20" barrel with a rifle-length gas system. So my setup, cool as it is with the A2 sights, is pretty far from what those sights were designed for so none of those elevation marks really mean anything if I decide to start screwing with the sights. Now realistically, I just have the sights set to a max point blank zero, and if the target is outside that range, it's not a target I need to be shooting at with an 11" 5.56.

But I tend to nerd out about these things and got to wondering, would the 0-600m sight assembly from an M4 carry handle make more sense to install in my upper? I'm assuming it's regulated for 62gr. from a 14.5" barrel with a carbine gas system since that is what it was originally designed to be used on. So while still not quite the same as what I'd be running it on, an 11.5" carbine is alot closer to a 14.5" carbine than it is to a 20" rifle. And perhaps the 55gr bullets help offset some of that velocity loss from the shorter barrel. So atleast the elevation markings somewhat more closely correlate with what the bullet is actually doing.

How far are you shooting?  I think you are over thinking it.  For practical ranges out to 200m you should be fine with BZO.

Agreed on all points. This question is more for academic mental masurbation purposes. If I got bored one day and took my little carbine to the range to play long range marksman with the iron sights, which would be the more appropriate sight assembly to have as far as the elevation settings actually matching the gun's ballistics.

I like to overthink these things.

This is where you hit the range with ammo and actual see what sight markings get you there, then record it.  Same thing if you had a Venier receiver sight.  Use a paint marker to mark the settings.

The sight assembly from a 14.5" M4 carry handle is the exact same as from a 20" M16A4 carry handle

The shorter sight radius makes the clicks coarser, negating some of the difference in trajectory.

If the 6/3 screw and wheel fits you’ll get twice as fine a resolution per click.  The range marks thus have twice as many clicks between them (there's still 25 clicks per Revolution the range marks are spread out more around the dial).  And the vertical space in the carry handle will allow more than one rotation (so getting lost in the dial is possible).  

Could be useful as marked through part of the range (probably up to 400 meters) but beyond that you’ll likely need to dope it out and make custom range marks. Getting the large peep, small peep shift useful might be the other tuning finesse required.