Gas Operation

Figure 3-34. Complete Time-Travel and Time-Velocity Curves for Gas-Operated Gun.

arc shown in fig. 3-34 which gives the theoretical time-travel and time-velocity curves for the com-

plete cycle.

As explained in the analysis of gas operation, the gun motion must be controlled so that the gun recoil movement is halted just as the bolt strikes the backplate and proper buffer action must be provided so that the gun velocity will be kept low for a reasonable amount of time before and after the bolt impact. This arrangement is necessary in order to insure that slight variation in the instant at which impact occurs will not cause erratic re bound action. No attempt will be made here to design an actual buffer but it will be assumed that a hydraulic buffer is used to produce the velocity characteristic shown in fig. 3 34. Instead of permitting the gun to recoil the entire distance opposed only by the barrel spring as shown in fig. 3-33, the hydraulic buffer starts to act at 0.18 second and reduces the gun recoil velocity from 5.8 feet per second to zero at 0.0210 second. At this point a positive stop is engaged and therefore the impact of the bolt on the backplate does not impart any rearward velocity to the gun mass. (Note that for

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