I've seen a lot of photos of SOF troops with detachable A2 sights mounted all the way foward on there ARs.    Being as how these guys were specially trained soldiers I'm under the impression that they purposely mounted the sights foward because it has some advantage over mounting the sight all the way to the rear.
    This however is in direct contridiction with what I hear a lot about a longer sight radius is better.


What are the advantages of the sight mounted at the front of the rail?    Disadvantages?

We don'tknow what context the use is really all about from just a picture. I remember when the first pics came out with SF guys carrying a detachable carry handle off the right side of a RAS forearm and people saying why whould they hold their rifle sideways and look down the sights like that. The answer of course was it's just a mode of transport for the carry handle was never intended to be used that way.

I haven't seen pic's like you discribe but I can not figure out one benefit to having an optic farther to the rear than needed as it reduces your field of view. That goes to say the same about moving your iron sights closer together reducing your sight radius as you mentioned.

Mode of transport I have to think again is the only reason.