An auto-loading firearm with magazine disconnect mechanism comprising: a frame defining a longitudinal axis; a magazine removably disposed in the frame and adapted for holding a plurality of cartridges; a hammer pivotably mounted in the frame; a trigger pivotably movable in the frame via a transverse trigger pin and operable to cock and release the hammer for discharging the firearm; a magazine disconnect member mounted below the trigger pin and comprising a horizontally orientated plate having a flat longitudinally elongated body, a front end, a rear end, and a central opening between the ends which receives at least part of the trigger therethrough, the plate selectively engageable with the trigger in response to removing and inserting the magazine, the magazine disconnect member movable between a blocking position in which the disconnect member engages the trigger when pulled and a non-blocking position in which the disconnect member does not engage the trigger when pulled; and a biasing member urging the magazine disconnect member into the blocking position, wherein inserting the magazine into the frame moves the magazine disconnect member from the blocking position to the non-blocking position; and wherein removing the magazine from the frame moves the disconnect member from the non-blocking position to the blocking position in which movement of the trigger is restricted to prevent cocking the hammer wherein the magazine disconnect member is slidably disposed in an elongate recess formed in the underside of the frame around the trigger, the firearm being characterized in that: the biasing member acting directly on an upward extending rearward angled sensing protrusion disposed on the rear end of the plate proximate to the magazine that is positioned in the frame to engage the magazine when inserted into the firearm and in response move the magazine disconnected member to the non-blocking position, the magazine disconnect member is substantially planar, and the magazine disconnect member and frame recess include mating complementary configured dovetailed sloping surfaces (86, 109) having a greater than a zero degree slope that slidably retain the magazine disconnect member in the frame. a frame defining a longitudinal axis; a magazine removably disposed in the frame and adapted for holding a plurality of cartridges; a hammer pivotably mounted in the frame; a trigger pivotably movable in the frame via a transverse trigger pin and operable to cock and release the hammer for discharging the firearm; a magazine disconnect member mounted below the trigger pin and comprising a horizontally orientated plate having a flat longitudinally elongated body, a front end, a rear end, and a central opening between the ends which receives at least part of the trigger therethrough, the plate selectively engageable with the trigger in response to removing and inserting the magazine, the magazine disconnect member movable between a blocking position in which the disconnect member engages the trigger when pulled and a non-blocking position in which the disconnect member does not engage the trigger when pulled; and a biasing member urging the magazine disconnect member into the blocking position, the biasing member acting directly on an upward extending rearward angled sensing protrusion disposed on the rear end of the plate proximate to the magazine that is positioned in the frame to engage the magazine when inserted into the firearm and in response move the magazine disconnected member to the non-blocking position, the magazine disconnect member is substantially planar, and the magazine disconnect member and frame recess include mating complementary configured dovetailed sloping surfaces (86, 109) having a greater than a zero degree slope that slidably retain the magazine disconnect member in the frame.