When I reassemble my Glocks I always make sure that the back of the recoil spring assembly (guide rod) is in the half moon shaped groove. When I take it apart it is always lower on the barrel lug (i.e. not in the semi-circle groove but right below it). I thought and or assumed that when I disassembled it, it simply dropped down. Just to be sure I took a flash light to my G30 and when I look through the slide it looks like the back of the guide rod is not in the semi-circle groove. It appears to be below it.  I have never had any malfunctions but I want to make sure that all is correct. Is it supposed to be in that groove at all times? If so what could I be doing wrong to cause it to drop down? Thanks for the help.  

Gravity causes it from racking the slide. (the lower lug of the barrel is where it should rest.) the cut out is for ease of assembly.

It is 100% normal.

Thank you ProCCW, that is the answer i was hoping for. Also thanks for the quick response. Happy shooting....