The M1 rifle is fed by an "en bloc" clip which holds eight rounds of .30-06 Springfield ammunition. When the last cartridge is fired, the rifle ejects the clip and locks the bolt open. The M1 is then ready to reload. Once the clip is inserted, the bolt snaps forward on its own as soon as thumb pressure is released from the top round of the clip, chambering a round and leaving it ready to fire. Although it is not absolutely necessary, the preferred method is to place the back of the right hand against the operating rod handle and press the clip home with the right thumb; this releases the bolt, but the hand restrains the bolt from slamming closed on the operator's thumb (resulting in "M1/Garand thumb"); the hand is then quickly withdrawn, the operating rod moves forward and the bolt closes with sufficient force to go fully to battery. Thus, after the clip has been pressed into position in the magazine, the operating rod handle should be released, allowing the bolt to snap forward under pressure from the operating rod spring. The operating rod handle may be smacked with the palm to ensure the bolt is closed.