The other day at the range I started having feeding issues.  First round on top of mag would feed fine, second round would jam on lip of mag.  I would clear jam, fire, and jam again.  Problem was present w/ all mags.  Issue was with only with rem 50gr HP. . which fed fine on other days.   60GR Hornady TAP fed fine. I have about 500 rounds through the rifle so far and this is the first issue I have had.    Upon closer inspection found screw that holds the A2 buttstock on was approx. 1 turn loose.  After tightening it seemed to clear up, but can't believe it could be that easy.  What else should I be looking for?  Thanks
njswampman