BUIS as a Primary, ask the Army?
The way it was explained to me was that some soldiers will never get an optic or a reflex, but may have occasion to mount a night sight/thermal when on guard duty around their bulk fuel dump, rations dump, etc., (get my drift--combat service support types).
So the officer in charge of the program modified the requirement to a more "fully capable" BUIS, if this was truelt to replace the carrying handle's capability.
By the way for what it is worth, our KAC 300-Meter BUIS (P/N: 98072)is the only one I know of with a National Stock Number (NSN) assigned.
As a component of the SOPMOD Kit, and Marine Recon's CQB Weapon, plus many others in US Military, something 25,000+ are in service. In the last 30 days in fact, over 1,000 to US Army unit's in Korea and 1,000+ to Germany. Also, some Marine Recon units use our 600M Fully Adjustable as well, but most of them we have subsequently modified to accept the removeable plastic aperture.
ColdBlue Sends.