Which weapon series includes a butterfly trigger as a key identification feature?

The weapon series that includes a butterfly trigger as a key identification feature is the PKB. The PKB, unlike its counterparts, features the butterfly trigger design which allows for easier operation in automatic fire modes. This type of trigger is designed to facilitate better control when engaging targets with sustained fire, particularly useful in mounted machine gun configurations.

The butterfly trigger design is distinctive and can be used to quickly identify the PKB when compared to other weapons in the PK series. The other models, such as the PKT, PKM, and PK, do not utilize this specific trigger design, which helps to clarify the identification of the PKB in operational and training contexts. Understanding these design features is crucial for proper identification and usage of the different weapon systems in diverse marine operations.