Use an Allen wrench to loosen the screw through the magazine body. Tap the magazine body to loosen the rear plate. You will usually hear the spring unwind as the rear plate comes loose. Disassemble and clean the magazine. Lube with spray dry lube (I like PTFE lubes, but there are others). When reassembling, preload the magazine spring by about 1 turn. Tighten the screw but there is no need to crank on it.