Unlocking

OCCURS (0.00334 SEC.)

Figure 1-37. Free Bolt Velocity Curve for First 0.010 Second.

it is negligible. For purposes of illustrations, it will be assumed here that the resistance offered by the buffer to compression is constant at 5500 pounds for the full compression of one-half inch and it will also be assumed that the expansion force of the buffer is 30 per cent of this value, or 1,800 pounds. On this basis and using equation 15, the barrel motion is as shown in fig. 1-35. The velocity loss due to die buffer is given as:

In this expression t is measured from the time the buffer engages. The forward velocity imparted to the barrel by the buffer is given as:

Ft 1650X32.2 ~\f= 40 t=,33(,t where t is measured from the time the forward motion of the barrel starts. This relation holds until the barrel has moved forward one-half inch. Since the barrel is subjected to a uniform accelera tion during this interval, the time required for the one-half inch movement can be determined by solving for t in the expression rH1330tz t=.00792 (see.)

After the barrel leaves the buffer it is further accelerated forward by the barrel spring. The movement remaining to the battery position is 0.0470 foot (fig. 1-34) and it may be assumed with little error that the average force exerted by the barrel spring over this distance will be the initial compression (400 pounds) plus approximately one-half the force resulting from the spring constant for the 0.0470-foot deflection

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