The semi-automatic mode of operation consists of the following steps:
1. The firer inserts a loaded magazine into the rifle.
2. The slide is then pulled rearward until it stops, and then is released sharply thereby allowing the bolt, propelled forward under recoil spring tension, to strip a live round from the magazine and chamber it during forward movement. As the bolt face contacts the breech of the barrel, a camming surface in the slide rotates the bolt forcing two locking lugs into matching recesses In the receiver. This will prevent the bolt from moving rearward during the initial high pressure following detonation of the cartridge. At this point, the hammer is cocked and held back by an engagement between the sear notch on the trigger and the hammer. (See drawing # 1A)
3. With the safety having been moved forward to "off", the firer then depresses the trigger which disengages the hairmer from the trigger sear. In this same motion of the trigger, the secondary sear moves forward slightly. The harmer, under pressure from the hammer spring, is propelled forward, striking the firing pin and detonating the cartridge. (See drawing * IB) The bolt will stay closed and locked until the chambered pressure drops to a safe level, and until a small amount of gas is vented from the barrel through the gas block blowing against the front of the slide with enough pressure to unlock the bolt (by reversing the camming action). The slide will then move rearward, carrying with it the bolt which extracts the spent cartridge and ejects it. The bottom of the bolt contacts and forces the hammer rearwards until it engages the secondary sear which will hold the hammer back. (See drawing # 1C) As the recoil spring compression overtakes the recoil Inertia, the slide will reverse and move forward, carrying the bolt which again strips a live cartridge from the magazine and forces it into the chamber. When the trigger is released, the sear engagement with the hammer will change. The trigger sear engages the hammer just before the secondary sear disengages from the hammer and moves rearward to its original position. By this time the bolt is locked into the receiver again and pressure applied to the trigger will again release the hammer to fire the cartridge and repeat the cycle.
Was this article helpful?