16 has a lower trigger piece 20 engageable by the firing digit of the user 39 s hand and an integrally formed boss 18 which is sized to be received within the internalized components of the trigger mechanism that is the boss 18 when the trigger is pulled to its firing condition as illustrated by the phantom line in fig1 is moved into the internal cavity of the frame in which the trigger mechanism is housed thus the boss of the trigger member 16 is substantially exposed when the trigger is in its latent prefired condition and is moved into the internal cavity of the firearm when the trigger is pulled to the fired condition shown in phantom line of fig1 in accordance with a further object of the invention a discharge preventing opening 40 is formed in the boss portion 18 of the trigger member 16 so as to be disposed tangentially or in very close proximity with the frame 14 of the firearm as illustrated in fig4 the opening 40 is again correspondingly sized and shaped to receive the shank member 38 of a lock member 34 in this way the u shaped member 38 of the lock can initially be unfastened from the lock housing 34 placed through the opening 40 in the boss.