Abstract: Trigger groups for semi-automatic firearms have a frame, a hammer connected to the frame and movable between a cocked position and a striking position, the hammer being biased toward the striking position, a trigger element connected to the frame and movable by a user between a forward position and a rearward position, a selector connected to the frame and movable between at least a first position and a second position, a disconnector having a hammer engagement facility adapted to selectably engage the hammer, a disconnector control element movable between a first control position and a second control position, the disconnector being operably engaged to the disconnector control element, the disconnector operable to move in a first range of motion when the disconnector control element is in the first control position, and in a second range of motion when the disconnector control element is in the second control position.

Abstract: A fire control group has a receiver having opposed sidewalls defining a space configured to receive a fire control group, the opposed sidewalls each defining a pivot pin aperture, the pivot pin apertures being registered with each other, a fire control group including a trigger received in the space, the fire control group defining a transverse pivot pin passage configured to be registered with the pivot pin apertures of the receiver, the fire control group including a pivoting operational element, the fire control group including a pivot pin supporting the pivoting operational element and received in the transverse pivot pin passage and the pivot pin apertures, the firearm having a hand grip aft of the trigger and defining a screw aperture, and a grip screw engaging the hand grip and engaging the fire control group. The grip screw may occupy a medial plane of the firearm.

Abstract: Trigger groups for semi-automatic firearms have a frame, a hammer connected to the frame and movable between a cocked position and a striking position, the hammer being biased toward the striking position, a trigger element connected to the frame and movable by a user between a forward position and a rearward position, a selector connected to the frame and movable between at least a first position and a second position, and a plurality of retention facilities each operable to selectively restrain the hammer in the cocked position, and when the selector is in the second position to enable discharge of the firearm in response to movement of the trigger to the forward position after movement to the rearward position and to enable an additional discharge of the firearm upon release of the trigger to the forward position.

Abstract: Trigger groups for semi-automatic firearms have a hammer, a trigger element, a sear, a selector, and a disconnector assembly, the disconnector assembly operable when the selector is in a first position to retain the hammer in the cocked position in response to release of the trigger element to the rest position subsequent to discharge of the firearm by pulling the trigger element, and the disconnector assembly operable when the selector is in a second position to release the hammer to the striking position in response to release of the trigger element to the rest position subsequent to discharge of the firearm by pulling the trigger element, such that the firearm discharges once per cycle of the trigger element when the selector is in the first position, and fires once for each forward or rearward motion of the trigger element when the selector is in the second position.

Abstract: Trigger groups for semi-automatic firearms have a frame, a hammer connected to the frame and movable between a cocked position and a striking position, the hammer being biased toward the striking position, a trigger element connected to the frame and movable by a user between a forward position and a rearward position, a selector connected to the frame and movable between at least a first position and a second position, a disconnector having a hammer engagement facility adapted to selectably engage the hammer, a disconnector control element movable between a first control position and a second control position, the disconnector being operably engaged to the disconnector control element, the disconnector operable to move in a first range of motion when the disconnector control element is in the first control position, and in a second range of motion when the disconnector control element is in the second control position.

Abstract: Trigger groups for semi-automatic firearms have a frame, a hammer connected to the frame and movable between a cocked position and a striking position, the hammer being biased toward the striking position, a trigger element connected to the frame and movable by a user between a forward position and a rearward position, a selector connected to the frame and movable between at least a first position and a second position, and a plurality of retention facilities each operable to selectively restrain the hammer in the cocked position, and when the selector is in the second position to enable discharge of the firearm in response to movement of the trigger to the forward position after movement to the rearward position and to enable an additional discharge of the firearm upon release of the trigger to the forward position.

Abstract: Trigger groups for semi-automatic firearms have a hammer, a trigger element, a sear, a selector, and a disconnector assembly, the disconnector assembly operable when the selector is in a first position to retain the hammer in the cocked position in response to release of the trigger element to the rest position subsequent to discharge of the firearm by pulling the trigger element, and the disconnector assembly operable when the selector is in a second position to release the hammer to the striking position in response to release of the trigger element to the rest position subsequent to discharge of the firearm by pulling the trigger element, such that the firearm discharges once per cycle of the trigger element when the selector is in the first position, and fires once for each forward or rearward motion of the trigger element when the selector is in the second position.

Abstract: A firearm barrel has an elongated body defining a bore and defining a bore axis, the body defining a breech end and an opposed muzzle end, a chamber defined in the breech end and contiguous with the bore; the bore having an interior surface having a plurality of alternating lands and grooves, the grooves being surfaces separated from the bore axis by first radius, the lands being surfaces separated from the bore axis by second radius less than the first radius and the lands and grooves being straight elements parallel to the bore axis, such that no spin is imparted to a projectile propelled down the bore. The lands and grooves may extend from the chamber to the muzzle end. The bore may have a constant cross-sectional profile along its length.

Abstract: Pistols with frame inserts have a frame having a grip, the frame having spaced apart upper sidewall portions having upper edges defining a slide interface plane, the upper sidewall portions being planar elements each having inner faces facing each other and exterior faces facing away from each other, each upper sidewall portion defining a side opening adjacent to the slide interface plane and having a perimeter spaced apart from the slide interface plane, a frame insert including pistol action components connected to the frame, and the frame insert having opposed insert sidewalls, each frame insert sidewall having a selected portion registered with and occupying a respective one of the side openings of the frame. The frame may define a cavity width between selected portions of the inner faces adjacent to the frame side openings, and wherein the frame insert has a width at the selected portion greater than the cavity width.

Abstract: A firearm barrel has an elongated body defining a bore and defining a bore axis, the body defining a breech end and an opposed muzzle end, a chamber defined in the breech end and contiguous with the bore; the bore having an interior surface having a plurality of alternating lands and grooves, the grooves being surfaces separated from the bore axis by first radius, the lands being surfaces separated from the bore axis by second radius less than the first radius and the lands and grooves being straight elements parallel to the bore axis, such that no spin is imparted to a projectile propelled down the bore. The lands and grooves may extend from the chamber to the muzzle end. The bore may have a constant cross-sectional profile along its length.

Abstract: Pistols with frame inserts have a frame having a grip, the frame having spaced apart upper sidewall portions having upper edges defining a slide interface plane, the upper sidewall portions being planar elements each having inner faces facing each other and exterior faces facing away from each other, each upper sidewall portion defining a side opening adjacent to the slide interface plane and having a perimeter spaced apart from the slide interface plane, a frame insert including pistol action components connected to the frame, and the frame insert having opposed insert sidewalls, each frame insert sidewall having a selected portion registered with and occupying a respective one of the side openings of the frame. The frame may define a cavity width between selected portions of the inner faces adjacent to the frame side openings, and wherein the frame insert has a width at the selected portion greater than the cavity width.

Abstract: Pistols with frame inserts have a frame having a grip, the frame having spaced apart upper sidewall portions having upper edges defining a slide interface plane, the upper sidewall portions being planar elements each having inner faces facing each other and exterior faces facing away from each other, each upper sidewall portion defining a side opening adjacent to the slide interface plane and having a perimeter spaced apart from the slide interface plane, a frame insert including pistol action components connected to the frame, and the frame insert having opposed insert sidewalls, each frame insert sidewall having a selected portion registered with and occupying a respective one of the side openings of the frame. The frame may define a cavity width between selected portions of the inner faces adjacent to the frame side openings, and wherein the frame insert has a width at the selected portion greater than the cavity width.

Abstract: A firearm barrel has an elongated body defining a bore and defining a bore axis, the body defining a breech end and an opposed muzzle end, a chamber defined in the breech end and contiguous with the bore; the bore having an interior surface having a plurality of alternating lands and grooves, the grooves being surfaces separated from the bore axis by first radius, the lands being surfaces separated from the bore axis by second radius less than the first radius and the lands and grooves being straight elements parallel to the bore axis, such that no spin is imparted to a projectile propelled down the bore. The lands and grooves may extend from the chamber to the muzzle end. The bore may have a constant cross-sectional profile along its length.

Abstract: A firearm cartridge has a case defining an interior chamber and having a case mouth, an elongated projectile having a forward end and a rear end, a sabot assembly having an exterior sized to be closely received in the case mouth, and defining an interior passage adapted to closely receive the projectile, and the projectile including a stabilizer at the rear end. The stabilizer may include fins. The projectile may include a circumferential groove at an intermediate portion between the forward end and rear end. The sabot assembly includes a mating feature adapted to engage the circumferential groove to limit axial motion of the projectile with respect to the sabot assembly. The projectile may define a plurality of circumferential grooves. The sabot assembly may include a plurality of mating features adapted to engage the circumferential grooves. The sabot assembly may include a plurality of elements arranged about the projectile.

Abstract: Trigger groups for semi-automatic firearms have a frame, a hammer connected to the frame and movable between a cocked position and a striking position, the hammer being biased toward the striking position, a trigger element connected to the frame and movable by a user between a forward position and a rearward position, a selector connected to the frame and movable between at least a first position and a second position, a plurality of retention facilities each operable to selectively restrain the hammer in the cocked position, and when the selector is in the first position to enable discharge of the firearm in response to movement of the trigger to the rearward position, and when the selector is in the second position to enable discharge of the firearm in response to movement of the trigger to the forward position after movement to the rearward position.

Abstract: Trigger groups for semi-automatic firearms have a frame, a hammer connected to the frame and movable between a cocked position and a striking position, the hammer being biased toward the striking position, a trigger element connected to the frame and movable by a user between a forward position and a rearward position, a selector connected to the frame and movable between at least a first position and a second position, a plurality of retention facilities each operable to selectively restrain the hammer in the cocked position, and when the selector is in the first position to enable discharge of the firearm in response to movement of the trigger to the rearward position, and when the selector is in the second position to enable discharge of the firearm in response to movement of the trigger to the forward position after movement to the rearward position.

Abstract: Trigger groups for semi-automatic firearms have a hammer, a trigger element, a sear, a selector, and a disconnector assembly, the disconnector assembly operable when the selector is in a first position to retain the hammer in the cocked position in response to release of the trigger element to the rest position subsequent to discharge of the firearm by pulling the trigger element, and the disconnector assembly operable when the selector is in a second position to release the hammer to the striking position in response to release of the trigger element to the rest position subsequent to discharge of the firearm by pulling the trigger element, such that the firearm discharges once per cycle of the trigger element when the selector is in the first position, and fires once for each forward or rearward motion of the trigger element when the selector is in the second position.

Abstract: Trigger groups for semi-automatic firearms have a frame, a hammer connected to the frame and movable between a cocked position and a striking position, the hammer being biased toward the striking position, a trigger element connected to the frame and movable by a user between a forward position and a rearward position, a selector connected to the frame and movable between at least a first position and a second position, and a plurality of retention facilities each operable to selectively restrain the hammer in the cocked position, and when the selector is in the second position to enable discharge of the firearm in response to movement of the trigger to the forward position after movement to the rearward position and to enable an additional discharge of the firearm upon release of the trigger to the forward position.

Abstract: Trigger groups for semi-automatic firearms have a frame, a hammer connected to the frame and movable between a cocked position and a striking position, the hammer being biased toward the striking position, a trigger element connected to the frame and movable by a user between a forward position and a rearward position, a selector connected to the frame and movable between at least a first position and a second position, and a plurality of retention facilities each operable to selectively restrain the hammer in the cocked position, and when the selector is in the second position to enable discharge of the firearm in response to movement of the trigger to the forward position after movement to the rearward position and to enable an additional discharge of the firearm upon release of the trigger to the forward position.

Abstract: Trigger groups for semi-automatic firearms have a hammer, a trigger element, a sear, a selector, and a disconnector assembly, the disconnector assembly operable when the selector is in a first position to retain the hammer in the cocked position in response to release of the trigger element to the rest position subsequent to discharge of the firearm by pulling the trigger element, and the disconnector assembly operable when the selector is in a second position to release the hammer to the striking position in response to release of the trigger element to the rest position subsequent to discharge of the firearm by pulling the trigger element, such that the firearm discharges once per cycle of the trigger element when the selector is in the first position, and fires once for each forward or rearward motion of the trigger element when the selector is in the second position.