While there are 9mm conversion kits for the AUG, they have a very bad reputation, and only number in the few hundreds. They're prized for their rarity, not their usefulness. The AUGs that Steyr makes in 9mm are supposed to be pretty reliable, though they aren't very popular compared to the MP5. Though a scoped SMG with a 16" barrel does have its uses....
As for a 7.62mm, I've never seen a mention of it, though I wouldn't be suprised if Steyr hadn't made at least one protoype for one of the many NATO LMG competitions. However, the production automatic rifle version of the AUG, the AUG HBAR, is 5.56mm. Relevant photo at
http://world.guns.ru/machine/mg21-e.htm (which is a site that'd be of interest to everyone following this thread).
One important thing to remember for game purposes (at least in campaigns currently set in the US) is that only a few were imported into the US before the assault weapons ban in the early 90s, and Steyr has shown no interest in retooling for the civilian market. As a result, AUGs go for thousands nowdays. So unless your pc's are members of law enforcement or the military, a legal AUG will be
costly.
Quick game stats for both
Steyr AUG 9mm
Type: 9mm Assault Rifle
Dmg: 2d8
Crit: 20
Type: Ballistic
Range increment: 70
Rate of Fire: S,A
Ammo: 25 box
Size: Large
Weight: 8 lbs.
Purchase DC: 20
Restriction: Res(+2)
Other notes: Integral standard weapon scope
Photo at
http://remtek.com/arms/steyr/aug/aug9/aug9mm.htm
Steyr HBAR
Type: 5.56mm Automatic Rifle
Dmg: 2d8
Crit: 20
Type: Ballistic
Range increment: 90
Rate of Fire: A
Ammo: 30 box or 42 box
Size: Large
Weight: 11 lbs.
Purchase DC: 21
Restriction: Mil(+3)
Other notes: Integral standard weapon scope
Photo at
http://remtek.com/arms/steyr/aug/aug24/special/hbart.htm
Note that I dont agree with the ranges given for weapons in the d20M book, but I kept these ranges in scale with those.