## Lb

The striking energy of the bolt is:

If it is assumed for purposes of estimation that the backplate offers a constant resistance of 13.700 pounds, the deflection of the elastic member under the impact will be:

The data derived in the preceding analysis are used to complete the motion curves of fig. 2-30 for the 0.001 second interval during which the backplatc buffer acts.

### 9. Motion of bolt after reversal at backplate

The holt leaves the backplate with a velocity of 36.0 feet per second, and as it moves in counter-recoil, its motion is aided by the compressed driving spring. This action will continue until the bolt reengages with the accelerator lever when the bolt displacement from the firing position is equal to 0.28 foot.

The bolt motion under the influence of the driving spring can be determined by essentially the same method previously employed for analyzing the effect of the springs. (Cf. fig. 2-32.) The first step is to draw a horizontal line at minus 36 feet per second to represent the free bolt velocity. In this case, the subsequent procedure must be slightly modified because the action of the spring is aiding the motion of the bolt rather than retarding it. At the start of the return motion of the bolt, the bolt driving spring is compressed 1.008 feet and hence the initial compression of the spring is:

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