For AUG A3 BB you need these two parts. Not apply to NATO stock version.
1.
http://www.riflegear.com/p-560-raddl...r-stg-556.aspx
2.
http://www.riflegear.com/p-561-raddl...rofit-kit.aspx
For extending your AUG A3 OLA to 30" you need this part.
1.
http://mfiap.com/i-11658336-mfi-hk-s...1-0-pitch.html
2. or you can find a 20" or 24" US made AUG barrel.
http://www.pjs-steyraug.com/augusrparts.html
Finally, buy some wood stick and make your own 10/30 AUG mags.
Thanks