While early (1949–50) Soviet models had spring-loaded firing pins, which held the pin away from cartridge primers until struck by the action's hammer, most variants of the SKS have a free floating firing pin within the bolt. Because of this design, care must be taken during cleaning (especially after long storage packed in Cosmoline) to ensure that the firing pin can freely move and does not stick in the forward position within the bolt. SKS firing pins that are stuck in the forward position have been known to cause accidental "slamfires" (the rifle firing on its own, without pulling the trigger and often without being fully locked). This behavior is less likely with the hard primer military-spec ammo for which the SKS was designed, but as with any rifle, users should properly maintain their firearms. For collectors, slamfires are more likely when the bolt still has remnants of Cosmoline embedded in it that retards firing pin movement. As it is triangular in cross section with only one way to properly insert it (notches up), slamfires can also result if the firing pin is inserted in one of the other two orientations.