Quoted:
G3 pattern if you want accuracy, FAL pattern if you want AK level reliability.
The G3/HK91 is everybit as reliable as the FAL. They are equals to one another, but the individual will determine which is better.
Here's a primer for you:
http://www.youtube.com/watch?v=Sl4p7qptO0A&feature=related
The G3 really doesn't have a gas system semi-auto operation, just the chamber flutes. With properly cut fluting, you can't make the gun stop. My PTR-91K hasn't jammed. Ever. I cannot make it stop working, I fired 2K of 308 before I ever cleaned it.
PTR has a list of ammo that may or may not work in the gun, but the gun has preferences.
I've shot the dreaded Indian w/o issue, as well as Lith, Radway, MEN, DAG, Silver Bear, Brown Bear, Lake City M80 ball (delinked from belts), M118LR, M118SB, Winchester 7.62mm Nato, Wolf, and Federal all w/o issues. Some PTR owners haven't been as lucky though.
Upgrades I did: MFI low rail mount, HK Furniture, and a heavy buffer. Recoil is about equal to an AK in 7.62X39mm now!