A trigger mechanism including a top sear for engaging a cocking piece, a transfer arm for engaging the top sear, and a safety lever and second stage sear which engages the transfer arm. The safety lever prevents unintentional firing of a firearm with the trigger mechanism. A bottom sear cooperates with the safety lever and the second stage sear. A reset spring biases the transfer arm. A single stage operation involves both a first stage spring and second stage spring upon trigger load application. In a two-stage operation, the first stage spring is engaged and then the second stage spring is also engaged. A selector pin provides flexibility to alter the mode of operation of the trigger mechanism between single stage trigger operation and a double stage trigger operation.