left under the power of its spring not shown to hit the bolt 10 to fire the round the invention safety mechanism is of exceedingly simple configuration and comprises a cam 22 the motion of which is controlled by a spring 24 and which parts operate in conjunction with a sliding sear blocking plate 26 the cam 22 is provided a hexagonal hole into which a hex portion of a rod not shown fits the rod is indicated by the axis 31 in fig2 as is well known in regard to firearms in general and especially with respect to the type of firearm for which the invention is designed the two arrows associated with the bolt 10 and striker 14 define a line of motion along which those two elements move the finger 32 of the cam 22 in the 34 safe 34 position extends up into this line of motion because of that extension up into or across that line of motion manual cocking of the bolt 10 as indicated by the arrow in fig2 first to the right and then to the left back to the fig2 position will cause the bolt to strike the finger 32 thus automatically moving the safety mechanism comprising the parts 22 24 26 and 30 from the fig1 34 safe 34 position to the fig2 34 fire 34 position likewise the hook 18 of the sear 16 moves into and out of that line of motion to permit or to check the motion of the striker 14 by engagement or no engagement with the striker finger 20 as shown in fig1 the cam 22 has been rotated in the counterclockwise direction to its blocking or 34.