u2032 thus leading to a corresponding rotation of the snap lever 13 up to cause the disengagement thereof from the foot 6 u2032 of the firing pin which therefore snaps forward to activate the bullet primer a plurality of springs 15 are provided in order to return the drive mechanism to its initial position after a shot and to be able to operate a new shot the operating sequence of the drive mechanism 5 is shown in fig8 a to 12c fig8 a and fig8 c are schematic right and left elevation views of the drive mechanism 5 and the firing pin 6 fig8 b is an enlargement of the encircled portion in fig8 c these figures show the drive mechanism 5 at rest before the user activates the trigger t the prominence 14 of the snap lever 13 holds the firing pin 6 thus remaining stationary fig9 a and fig9 c are schematic right and left elevation views of the drive mechanism 5 and the firing pin 6 and show an instant following that respectively shown in fig8 a and 8c fig9 b is an enlargement of the encircled portion in fig9 c these figures show the drive mechanism 5 when the user begins to press the trigger t in order to rotate it on the y axis the above described kinematic chain formed by the elements 8 13 leads to the rotation of the snap lever 13 on the pin 13 u2032 and to the lowering of the prominence 14 in fig9 a 9c the prominence 14 has lowered and is at the limit point where the foot 6 u2032 is about to disengage fig1 a and fig1 c are schematic right and left elevation views of the drive mechanism 5 and the.