An auto-loading firearm having a system for switching the firearm between a live fire mode and a training mode, the firearm comprising: a trigger movable between a home position and a depressed position; a sear mechanism movable to release a hammer or striker to discharge the firearm; a transfer mechanism extending between the trigger and the sear mechanism, the transfer mechanism having: a first transfer portion (36, 320) connected to the trigger, and a second transfer portion (42, 322) for moving the sear to discharge the firearm, the first and second transfer portions releasably attachable to one another having a connected position wherein movement of the first transfer portion results in movement of the second transfer portion, and having a disconnected position characterized by: in said disconnected position the first and second transfer portions are movable with respect to one another and movement of the trigger does not result in movement of the sear mechanism, discharge of the firearm thereby prevented; a selector switch movable between a live fire position and a training mode position, wherein the transfer portions move to the connected position in response to movement of the selector switch to the live fire position, and wherein the transfer portions move to the disconnected position in response to movement of the selector switch to the training mode position; and a selectively engageable trigger resetting mechanism for automatically returning the trigger from its depressed position to its home position when the first and second transfer portions are in the separated position. a trigger movable between a home position and a depressed position; a sear mechanism movable to release a hammer or striker to discharge the firearm; a transfer mechanism extending between the trigger and the sear mechanism, the transfer mechanism having: a first transfer portion (36, 320) connected to the trigger, and a second transfer portion (42, 322) for moving the sear to discharge the firearm, a first transfer portion (36, 320) connected to the trigger, and a second transfer portion (42, 322) for moving the sear to discharge the firearm, the first and second transfer portions releasably attachable to one another having a connected position wherein movement of the first transfer portion results in movement of the second transfer portion, and having a disconnected position characterized by: in said disconnected position the first and second transfer portions are movable with respect to one another and movement of the trigger does not result in movement of the sear mechanism, discharge of the firearm thereby prevented; a selector switch movable between a live fire position and a training mode position, wherein the transfer portions move to the connected position in response to movement of the selector switch to the live fire position, and wherein the transfer portions move to the disconnected position in response to movement of the selector switch to the training mode position; and a selectively engageable trigger resetting mechanism for automatically returning the trigger from its depressed position to its home position when the first and second transfer portions are in the separated position.