What factor is most crucial for maintaining the reliability of a blowback firearm?

The most crucial factor for maintaining the reliability of a blowback firearm is the quality of ammunition. This is because blowback systems rely heavily on the pressure generated by the cartridge to cycle the action. Poor-quality ammunition can lead to inconsistent pressure levels, which can affect the firearm's ability to function properly. For example, underpowered ammunition may not generate enough force to fully cycle the firearm, leading to failures to eject or feed. Conversely, overly powerful ammunition can cause excessive recoil and potential damage to the firearm.

In blowback operations, the design is such that the bolt is held in place by the resistance of the cartridge case against the chamber. If the ammunition is of low quality, it can create issues such as misfiring or other operational failures. Therefore, using reliable, high-quality ammunition is essential for ensuring that the blowback action operates as intended and maintains reliable performance during firing.

While other factors, such as operator technique, correct lubrication, and the weight of the firearm, do contribute to overall firearm performance, they do not have as direct an impact on the blowback mechanism's operation as the quality of the ammunition used.