Double hackbut

This double-length rifle uses a pair of trunnions to mount its barrel into a swiveling mechanism fastened to the top of a lightweight, two-wheeled carriage. It takes a full-round action to set up the carriage. The carriage has a hind leg, allowing the wielder to wheel the device about and immediately prop it for stability during combat. Unlike other two-handed firearms, you must fire the double hackbut while it is mounted, or else firing it imparts a –4 penalty on attack rolls and the recoil knocks you prone. A Large or larger creature can fire a double hackbut one size smaller than itself without the gun’s mounting as a normal two-handed weapon and without the danger of being knocked prone, but takes the normal penalty for firing an inappropriately sized weapon. This is an early firearm.