People have been shooting out to very long ranges with iron sights for a long time. I view the addition of high-quality, precise iron sights to a precision rifle as something to be done as a matter of course.  Doing so will provide you with the opportunity to use iron sights in lieu of the optic, and that experience could come in very handy if the optic fails or is otherwise unusable.

The short-range. flip-up BUIS commonly used, the rear sight often having no windage adjustment whatsoever, are completely unsuitable for long-range, precision work.

High-quality, long-range BUIS will be useful to you to the extent you practice with them.  Simply having them (zeroed, of course) is not enough.  You will need to practice adjusting them at various ranges in order to become proficient with them.

The rear sight you pictured seems to be a plausible choice, and the Matech is another, albeit not for extreme ranges;  Either one folds up and when deployed is far more capable than the plastic BUIS one sees commonly, and which are intended for short range use.  Nothing intrinsically wrong with that choice, BUT I find it unfortunate that many shooters opt for limited-adjustment rear sights on their shorty ARs, in lieu of ones with full range of adjustments.

I don't doubt your scope will let you reach out further than iron sights, no matter how well made, although there are some very fine ($500) iron sights available that will do all that one could ask.  Not exactly low-profile, nor QD, though.  But, if you want low-profile iron sights that will work at long range, consider the NM front and rear sights on a NM Garand or NM M1A.  With a properly Scout-Scoped NM Garand and/or NM M1A, the QD scope can be arranged to hit (through reticular hold-overs) out to 600 yds.

The point is that decent, fully adjustable BUIS are available, albeit seldom seen, and, I suspect, even less often used. Putting such rear sights on a short-barreled 5.56 carbine would probably be a waste of money, although mounting a Matech or similar sight on a 20" barreled AR should be useful, as long as the shooter practices with it. 

I think what we see nowadays is that shooters choose equipment, such as rear sights and slings, not understanding the benefits of more elaborate equipment.  I believe that they do not fully understand the full range of choices available to them, and so choose the simplest, least expensive option. 

 

I concur with JJREA in his rebuttal to your previous statements.  All my optics are carefully and deliberately mounted so as to be very quickly dismounted.  Hell, long ago--very long ago-- I was brazing wingnuts on Weaver fastening nuts in order to take them off quickly.  That was before a lot of better alternatives were available.  Nowadays, at the very least, Leupold QRW mounts, and better still, throw-lever mounts.  The Leupolds, being the slower of the two mounting systems, take about 5 seconds to dismount; the throw levers being rather quicker.

There are very good top-mounted BUIS available, which mimic the original A2 iron sights, as well as the issued MaTech.

What I find interesting is that the 45 deg offset sights might eliminate the need to remove the optic for very close shots.  I'm investigating this alternative by buying a cheapo set of non-foldable 45 deg offset sights.  I find it curious in the extreme that there are offered foldable 45 deg offset sights.  Presumably, such sights are to be used for close range, and instantly.  Does one have the time to flip both of them up instantly?  I think not.  Thanks to the previous poster in this thread for implanting the idea in my head. 

I should add that 45 deg offset sights are available with all the bells and whistles, including Trit front sight inserts, as well as full range of adjustability that equals the original A2 sighting system.  Some might find this capability useful, but I think that if a long shot is required, one will have the time to remove the optic, and use the conventionally-mounted BUIS.  Being no expert, I believe the best use of 45 deg offset sights is for the close-to-middlin' range shot that is so close, and so transient, that the optics cannot be removed, nor can the flip-up BUIS be deployed quickly enough to make the shot.  In short, transitioning to the 45 deg offset sights is [b]instant, or almost so.  YMMV, and some of this is new to me, so forgive any misconceptions on my part.

As I said previously, there are iron sights, for most any rifle, that will do out to any range that your eyes can see, and the rifle will hit, accurately.  Last I looked, the long-range rail-mounted rear sight was about $500, and it is a marvel to behold.  Obviously, it's a semi-permanent mount, and almost impossible to use in conjunction with any reasonably low-mounted-optic. 

Let me explain what I see as suitable BUIS on a precision rifle.  I envision robust, lightweight sights that can be quickly be deployed in the event the optic is unavailable or unusable for some reason, the primary optic being likewise quickly and easily removable.  In using such BUIS, it definitely should allow the shooter to take the cheek weld that their rifle/stock is set up to use with the (presumably) primary optical sighting device.  No adjusting the cheek riser, and no chin weld.  BUIS are useable, once deployed, with same cheek weld as the usual optic.  The BUIS, on a long-range rifle should have a reasonable, precise, range of adjustment, and allow the use of various rear sight apertures.  The threaded sight elevation arm (which accepts threaded apertures) of most commonly available aftermarket rear sights makes an excellent ghost ring rear sight, albeit for very close ranges.  The front sight should allow for user-defined front sight posts to be installed, and such front sight posts to be protected by wings that cannot possibly be confused with the front sight post; IOW, military, curved wings.

Many old-timers had installed on their rifles all sorts o iron front and rear sights, and they could shoot out to 1000 yds with them, and accurately.  Those sights were permanent installations, and very specialized in their (usually) target range use  I don't see anything like what they used available in flip-up BUIS, but I do see BUIS that will shoot out to 500-600 yds, perhaps more with some tweaking.

In my mind, BUIS on a precision rifle are for the unexpected, but possible failure/unavailability of the primary optic.  Having such good BUIS saves the shooter from having a (at least) a temporarily useless rifle, and allows the user some options, and without recourse to possibly unobtainable outside help.  I don't claim that any but the most exceptionable BUIS will come close to a good long-range optical rig, but the exceptionable iron BUIS do exist. 

That's my concept.  Whether or not it suits your needs/desires is, of course, up to you.  Whether one chooses to bear the (significant) cost of such precision rifle BUIS, and practice with them is up to the shooter. 

I have a number of firearms.  I have made a point, over the years, to mount optics on some firearms which were never originally intended to have optics, mainly on account of my older eyes becoming increasingly unable to use long-range iron sights effectively.  Likewise, I have installed very good iron sights on some firearms which seemed to me required them.  Just saying, so you have some perspective on what I've said.

Interesting story.  I've also seen shooters have various sorts of malfunctions which could have been remedied by prior planning for such eventualities.

A classic of this sort was an M1A shooter who had his extractor and its' spring launch itself into orbit during a Match.  The shooter did have a spare assembly, which he quickly installed.  The extractor was in its' sealed bag.

Unfortunately for the shooter, the newly installed extractor lasted a few shots before it, too, launched into oblivion.

Base cause for both failures was the shooter did not know that it was necessary to pre-fit M1A/Garand extractors, and to make certain that the pivot post was slightly recessed below the surface of the bolt.  Had he known that essential fact, it is unlikely he would have had the first failure, let alone the second. 

The lesson here is to always have a viable Plan "B" and to execute it properly. 

Without asking the identity of the "Big Name" mount mfr, how did one screw going astray cause the mount to malfunction?  Most rings use at least four screws to secure their caps, but how the rings are secured to the rail/receiver is a variable.  Not doubting you at all, just curious, and a fuller explanation might aid some people in avoiding problems in the future.