An inline hammerless percussion firing system for muzzleloader firearms with a striker having a firing pin and a striker spring to linearly drive the firing pin forward. A cocking button compresses the striker spring. A pivoting retainer acts against a nut connected to the cocking button to hold the cocking button forward and keep the striker spring compressed. A sear acts to prevent the striker from moving forward until released by a two piece trigger system in which a trigger and trigger edge pivot relative to each other with lost motion before releasing the sear, allowing the trigger edge to move out from below a safety notch in the sear, where firing is prevented, to below a firing notch in the sear to prevent accidental discharges from impact. The cocking button can be released by an uncocking button. Releasing a barrel catch resets firearm to the initial safe position.