Re: CJNG took down the Mexican Army helicopter in Jalisco with a Rocket Propelled Grenade [RPG]
The trigger group that came with the gun has had the 'sear' that swivels to allow full auto fire removed and pins welded in place to prevent it from being easily converted back, although in some case the selector switch and lettering is left in place, even though the Feuerstoß [full auto] capability has been disabled.
The surplus G3 trigger group has 'wings' on the stamped steal frame that prevent it from being slid into position on the cloned receiver, before the pins are pushed in to secure it. It's a fairly simply procedure to grind down the 'wings' in order to fit into the cloned receiver, but this is considered a full auto modification, and it's illegal to own it after it's been converted, unless you are a manufacturer, or security personnel [almost always US government/military] licensed to own automatic weapons.
Those that say, don't know. Those that know, don't say.