Also be sure that when you rack the rounds in that you pull the charging handle to the rear and let go. Do not ride the charging handle forward. If you try to " baby" the rounds in to the chamber you can have the type of problems you experienced.
Also, that looks like a kind of cheap aftermarket mag which could contribute to your problem.
Last edited by SSGN_Doc; 11-28-2012 at 07:25 AM.