Which type of action utilizes spring pressure and bolt weight to operate?

The type of action that utilizes spring pressure and bolt weight to operate is blowback action. In blowback systems, the force generated by the recoil from the fired cartridge is used to operate the action. When a round is fired, the expanding gases push the bolt rearward due to the inertia of the bolt assembly combined with the spring tension. The weight of the bolt and the strength of the recoil spring work together to ensure the bolt returns to its locked position before another round can be chambered.

This system does not rely on gas pressure as seen in gas-operated actions, where a portion of the gas from the firing process is redirected to cycle the action. Instead, blowback systems operate simply on the momentum from the recoil. This makes this type of operation relatively simple and effective, especially for smaller caliber firearms.

Understanding this mechanism is crucial for recognizing how different firearm systems function in various operational contexts, such as while engaged in small arms familiarization or operational readiness training within the Navy.