Figure 1-27. Time-Travel and Time-Velocity Curves (Complete Cycle).

sion is 206 pounds and the recoil distance is 10 inches, the spring rate will be 20.6 pounds per inch or 247 pounds per font. Realizing that this choicc is arbitrary, it will be assumed here that the selected values of F<,= 130 pounds and K=247 pounds per foot will result in a satisfactory spring.

Sincc the bolt weight and the characteristics of the driving spring have been determined, the basic design of the gun is now complete and the remaining task is to consider what performance this design may be expectcd to give.

3. Bolt motion equations

Since the bolt motion equations derived for plain blowback are all based onlv on the amount of bolt energy and on the characteristics of the driving spring, these equations arc not affected by the use of advanced primer ignition. (Of course, the values to be substituted in the equations are different, but the relationships between these values are not changed.) Therefore, the equations will not be derived again here but they arc listed for ready reference:

/\frr . Kd + F0 . F0 -1 M K LSm KD—F„_sm ■ KD+F.J

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