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Us M1 Mecanism The carbine is gas-operated, and has a short-stroke piston. As soon as bullet (a) is forward of gas port (b) in barrel, gas from the burning powder expands through gas port into gas cylinder and thrusts the piston (c) rearward. The piston strikes the operating slide (d), starting it into motion, and the piston is stopped after about 3/16" travel by the piston nut. As the operating slide starts to the rear, the operating slide spring {e} begins to be compressed. The operating slide moves about 5/16" before its cam contacts operating lug of bolt. This allows operating slide to gain speed to overcome inertia of the locked bolt, and also gives time for bullet to clear muzzle, allowing pressure in barrel to be reduced to outside pressure before bolt begins to unlock. As operating slide continues to the rear, it compresses the operating slide spring and cams the bolt counterclockwise to unlocked position. Extraction and ejection of fired cartridge case, withdrawal of firing pin to safe position inside bolt. and cocking of hammer occur as bolt moves rearward. When operating slide and bolt move forward, pushed by the compressed operating slide spring. the bolt strips top round from magazine and shoves it 'into chamber. When bolt reaches forward position, cam in operating slide rotates bolt clockwise so that locking lugs on either side of bolt head engage locking shoulders in receiver. The M1 carbine is of semi-automatic type (trigger must be squeezed and then released for each shot)     Safety (a) of carbine is engaged when rotated so that safety lever points down as shown. To load, engage safety, and insert loaded magazine (b) into magazine opening, making sure magazine snaps into place. With forefinger of right hand hooked over operating slide handle (c), pull operating slide to the rear and release it, closing the bolt. Striking rear of operating slide handle with heel of hand helps to close and lock bolt. To make piece ready for firing, rotate safety to disengaged position (safety lever to rear). To unload, engage safety, depress magazine catch (d) and remove magazine, pull operating slide to the rear and lock it in this position by depressing operating slide stop (e) so that it engages it detent in the receiver. Inspect chamber to make sure carbine is unloaded, and unload magazine. To operate its a single loader, pull operating slide to rear and lock in this position by depressing operating slide stop. Place it round in the chamber, seating it with thumb. Pull operating slide slightly to rear and release it. When operating slide is locked in rear position, avoid hitting butt of carbine on ground or jarring by other means as this is liable to release operating slide, and if cartridge is in chamber or loaded magazine is in carbine, the carbine will be inadvertently made ready to fire. Rear sight is adjustable for elevation by sliding aperture (f) on its ramp. Aperture is adjustable for 100, 200, 250, and 300 yds. Windage is adjusted by turning windage knob (g) One click of windage moves strike of bullet on target approximately) 1" for each 100 yds. of range. The rear sight base has graduations for windage launchers, sights, and design changes in parts including the safety, barrel, hammer, and bolt.     Prime contractors for production of U. S. cal..30 carbines were: Winchester Repeating Arms Co.; Inland Div., General Motors Corp.; RockOla Corp.; National Postal Meter Co.; International Business Machines Corp.; Underwood Elliott Fisher Co.; Saginaw Steering Gear Div. General Motors Corp.; Standard Products Corp.; Quality Hardware & Machine Corp. In addition there were many subcontractors and parts manufacturers.     The carbine proved extremely popular with most troops, and many civilian gun enthusiasts have since become intrigued with it. There are several reasons for this popularity, principal ones being that the carbine is light, handy, possesses a sporting rifle balance and appearance, and develops little recoil.