Air-soft gun shooting problem.?

I have a 445 FPS Air-soft DBoys Full Metal M16 SPR MK12 Mod. 0 AEG Rifle and i bought it off of Airsoft Megastore. I have the correct size BBs and i shoot, but the BBs don't always come out. Sometimes when i shoot, the BBs won't come out right when i shoot and the times they don't shoot out, they will just fall out. If the problem is obvious then i can fix it, but if it's a big problem and if you have somewhere you like to get your gun fixed, please tell me. I live in Senoia, Georgia.