A quality grease made for using in a load bearing application is the preferred method to lubricate a pistol or rifle. High temp axle grease or synthetic axle grease will do. Not withstanding that some parts may be better lubricated with oil BUT for the most part grease is best. Grease stays where you put it and will stay there for a long time. That is why you will find most new guns have grease on the slides, or grease on rifles that have been stored for 40 years. Usually only small internal parts may require grease, but for the most part anything that can be oiled can also be greased. AR-15, HK, FAL, AK grease it, Glock, 1911, and any other auto grease it. Little pocket auto in 22 or 25 cal. or revolver, oil it.