Its been mentioned in a few posts, but i will repeat. I have been working on this topic for years.
The best sighting optic in my opinion is an eotech. Some will say aimpoint, and they are great. But aimpoint is flawed, in that you are "aim" ing at
a "point". You have no peripheral vision without looking up. Any one that has ever aimed through a scope at a running deer will see the obvious
Now eotechs have their disadvantages. They take batteries, and are not magnified. SO, you over come that. A 3x magnifier on a quicktwist mount, AND
backup, flip up sights.
i have an AR-15 carbine with a free float handguard. I have troy flip up sights(front and back). I have an eotech 512 with a 3x aimpoint magnifier on
a quicktwist mount.
So you are in a firefight. With an eotech only, you can aim through the very large, parallax free(means your eye can look through at any angle and you
will still hit whatever you aim at). You also can leave both eyes open. This all is great for fast, close battle.
If needed you put your 3x magnifier on your rifle. The mount I use is the quicktwist mount. There is a small metal peg that stays mounted on your
rifle. You reach into your vest or pocket and pull out the 30mm magnifier. You seat it and twist, and it locks on. Takes 10 seconds if you are very
slow and deliberate. I can do it in 5. This magnifier sits directly in front of your eye, with the eotech mounted next. This gives a very clear, close
up view, with a parallax free illuminated reticle still in view. I can hit 2 liter bottles of water at 200 yards effortlessly.
And also mounted, you have backup sights. i like
as they are very fast and
easy to use.
one last thing. Google "co witnessing". basically you sight in your iron sights, and then move the eotech reticle to match. If your eotechs
batteries were to fail in a firefight, you flip up your sights and still get the added advantage of sighting through the large window of the eotech. I
have practiced this, and its much more effective than just iron sights.