The Machine Gun

be the net recoil velocity, or in other words the

velocity of retarded recoil.

The foregoing method would be very simple if the retarding force were constant or if the variation of this force with respect to time were known. However, when the force varies with recoil travel as it does with the springs assumed for purposes of analysis, a difficulty is encountered. In order to plot a graph showing the variation of the retarding force with respect to time, it is necessary to have a curve showing the variation of the recoil travel with respect to time, and the latter curve is one of those which yet remain to be determined.

This difficulty can be overcome by employing a proccss of successive approximation. While the powder gas pressures are acting, the loss in velocity resulting from the retarding effect of the springs will be relatively small and will be almost entirely due to the constant effect of the initial compression. The varying forcc due to the spring constant during this interval of time will almost certainly be negligible but, if necessary it can be approximated very closelv.

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