Front BUIS location on rail

[orionz06]

That's one reason I was asking. Though I didn't know why, I've seen pictures of 16" carbines set up by him, and others, with front flip-ups far rearward on the rail without obstruction by any other accoutrement.

The further out on the rail the slower it is to aim. The closer to the rear sight the faster it is to aim. Your index on the rifle will influence this a bit too. Think of it as a fine and coarse slider on a scale. Once out so far it begins to seem like you are wiggling the small weight around. This is an exaggeration of course but still the same principle. If you wanted to truly test it out I would start with some groups on paper with the sight at each end of the rail and see what the difference is. The ammo and mechanical accuracy of the gun will come into play too.

[rob_s]

I have spent a LOT of time/rounds with an irons-sights disspator configuration, so I like, and am familiar with, that sight radius quite a bit, almost always with the small aperture.

On a 16" barrel with 15" handguard, I would personally also be thinking about limiting what I can jam the muzzle into in terms of things like a 9-hole wall. I like to generally hold my front sight back the length of a Surefire X300 plus one slot for that reason, and I can remove the Surefire as-needed for tight holes.

[philpac33]

My main rifle has a 16" bbl with 15" rail. After much swapping of accessories I've settled for an Inforce/HSP WML at 12:00 as far forward as possible and the BUIS directly behind it. The angled activation of the WML makes having them so close together non-problematic.