Most magazines, particularly military ones, are designed to use the point of a bullet for dis-assembly.  Try to use something that will do the job without scratching the finish of the release mechanism.  A thin-topped ball-point pen might work in lieu of a bullet tip.  Clean the inside thoroughly, and consider a very thin film of oil on the inside of the body of steel mags.  Automobile wax on the exterior surface of blued steel mags.  Always put a thin film of oil on the spring.  Remove very thin surface rust ASAP, and if the spring shows any signs of pitting, use that particular uniquely-marked mag for range use, and buy replacement spring(s).

AR magazines are notorious for collecting dirt and crud, and their springs are likewise more subject to rust promoted by the crud adhering to them.  Magazines are a regular maintenance item.