1. Arquebus, a hand-gun; a species of fire-arm of the sixteenth century, resembling a musket

2. A Breechblock assembly and operating mechanism for a gas operating automatic loading fire-arm has a Breechblock slider adapted to be retracted by utilization of a gas pressure at the firing of the shotshell, a link is pivoted at the rear end of the slider so as to be swingable up and down and provided with swinging-movement limiting means, a Breechblock is adapted to be locked so as to tightly