Sure there is dude...perhaps you meant that it's not plainly visible?
On the AK it's under the screw that holds the grip on...there should be a tiny 1.5mm (might be 2mm?) allen key buried deep in there. Take out the grip screw and stick an allen key in to adjust. Same on the G36.
On the MP5K/FAL/(others where there's no motor cage), there's a set screw similar to the M4 grip