[Drakker]

In my experience jamming is primarily due to large particles stuck in the mag. Most of the time sand or gravel, but I've also seen broken BBs stuck in the springs. If the springs got wet they might also be badly rusted. Opening the mags and cleaning them should restore them. Oil in mags is a bad idea because it will gum them up pretty quickly when exposed to dust and dirt. If the mags are particularly dirty, a q-tip with isopropyl alcohol will help.