What kind of five shot groups at 100 yards should I expect from an AUG?
I'm not talking about the single best group you ever shot.

More like, you shoot 10 sets of groups with a 10 different loads, what would be the average group size?

I'm generalizing here....there is no need to start asking me a bunch of specific questions to dial it down to a gnats ass.

Tony

3"-5" with standard ball ammo.  Standard military grade accuracy.

How about 10 shot groups?
pics at links

https://www.ar15.com/forums/General/View-of-an-AUG-1-5X-Donut-of-Death/5-2609646/

https://www.ar15.com/forums/Armory/Steyr-AUG-at-the-Range/43-550723/

Very good. I love the random discussion in the background about some guy’s Mauser k98k.

Honestly,  with a modern current production AUG, this isn't that far off.  

Don't expect to be hitting 1 MOA groups.  That barrel has more contact points than an extended warranty sales strategy plan. And these aren't the Austrian Steyr made barrels.

Some people can do better, but if your mission statement is a sub 2 MOA gun on a new production unit, prepare to be disappointed.  

Be aware the pistol grip position and contact/non-contact can have a meaningful impact on POI and accuracy - with that varying from unit to unit

Also be aware that ammo selection can notably impact POI as well, with heavy ammo striking much higher than light ammo - again, notably variable from unit to unit.

My KelTec RDB outshoots my AUG.  Other people's AUG,'s (typical originals) can shoot much better.

I never had good results with mine but attributed it to trigger pull

My 2020 production AUG will do 1.5" to 3" off a bench at 100 yards with PMC 55 grain .223 and 5.56mm X-Tac. 62 grain M855 from Winchester and PMC produced similar groups.
I use a Vortex Strike Eagle 1-8x optic on a Rock River one-piece mount.
That was on my very first outing and, as has been discussed at length, the trigger pull was indeed the main limiting factor for me.
The mechanical accuracy of the AUG is pretty damn good in my view, with human factors and ammunition variability being the main limits to getting good groups.
But, at the end of the day, tight groups are not meant to be this rifle's Forte, just a nice side benefit.

My 2 2023 production AUGs have both given me numerous sub MOA groups (5 shot group, sandbag rest, no called alibis or averaging best 5 out of 10 BS). This is with an Aimpoint and 3X mag!!

On average, I'd say I'm getting 2-2.5MOA really trying hard across a variety of factory loads. Outstanding loads so far ADI (Australian Outback) 55gr Blitzking, Fed 50gr Tipped (old load from PSA sale 10 years ago) and Norma 77gr OTM. My typical defense loads like 62gr Speer Gold Dot, Fed Fusion and Fed Bonded Tactical 55gr are averaging around 2.5MOA. IMI 77gr Razercore is averaging 1.5MOA.

The trigger and my RDS "optics" are the biggest limiting factors. But mechanical accuracy is on par with my better AR's.

This is on the hight side. I would say 2-3" groups at 100.

It’s about the same as the average rack grade .mil AR. 2-3” at 100 is about right.