Which of the following describes the action type of the U.S. Rifle, caliber 30, model 1903A3?

The U.S. Rifle, caliber 30, model 1903A3, is described as a manually operated bolt-action rifle. This means the shooter has to manually operate the bolt to load a round from the magazine into the chamber, which requires using the bolt handle to unlock, pull back, and push forward to chamber the next round after each shot is fired. This action type is characteristic of many traditional military rifles from the era.

Manually operated bolt-action rifles provide reliability and accuracy, making them suitable for precise shooting scenarios, which was essential during the time of the 1903A3's use in military engagements. The design allows for a robust construction, which contributes to the rifle's durability under various conditions.

In contrast to this, lever-action rifles use a lever to cycle the action, semiautomatic rifles automatically cycle the action after each shot fired, and fully automatic rifles continue to fire rounds as long as the trigger is held down. These other action types involve different mechanisms that change how the rifle operates in terms of shooter input and rate of fire, setting them distinctly apart from the bolt-action operation of the 1903A3.