So as many know. The AUG known as the A3 M1 here in the USA can use a number of different rail housings and optic housings by way of the M1 receiver. Austria's Special Operations, Jagdkommando and their airborne unit, Jägerbataillon 25 has been using what we call the A3 SF (they call it StG77A2 KDO (AUG A2 Kommando) for nearly a decade: https://www.youtube.com/watch?v=U4Db8V38cLg
Jagdkommando:
Jägerbataillon 25
Essentially the main difference between the A3 SF and the A3 M1 (w/ factory optic) is that the SF model optic sits/is swept lower and has provisions for scope lens covers. Presumably to use red dot optics on top easier. Since the M1 optic sits at about the same cheekweld/overbore as a standard AR optic.
Of course, Steyr has what they call the A3 SF O. Which is essentially a full auto variant of the M1. Same of very similar optic housing of the M1 with a 20 in.barrel as opposed to a 16 in. barrel.
https://www.youtube.com/watch?v=cjltybUkeA4
Onto the new info. Now this appeared online quite a few months ago. But it appears that Austria is giving their non Special Ops, front line troopers (ie their front line infantry, professional soldiers) a new AUG. Dubbed the StG77A1 KPE: https://www.youtube.com/watch?v=Ljh_J8zQcJM This appears to an M1 like American consumers can buy. Except in this video it appears to have provisions to put on lens covers in the housing and more rails. 20 in. barrel which is how the Austrians roll for their main military.
https://www.youtube.com/watch?v=Ljh_J8zQcJM
Here's a couple articles on the procurement of the StG77A1 KPE. These images differ from the video a little. Considering the barrel has a bayonet lug(which Austria doesn't use bayonets) and the optic housing is identical (top rifles in the pics) to our M1 rifles. You'll notice the non QD front sling loops and the green colored trigger, etc) So it's not USA made.
https://translate.google.com/translate?hl=en&sl=de&u=http://strategie-technik.blogspot.com/2017/08/alles-gute-aug-40-jahre-sturmgewehr-77.html&prev=search
http://sipol.at/en/2017/03/30/new-gear/
No idea on which (if not both) KPE variants will be fielded by Austrian troops. I guess your average Austrian soldier won't be getting a red dot anytime soon. :D I guess the new KPE variants will make it easier to mount lights and lasers than the old A1/STG77 did.