T

To obtain the total time of action of the powder gases, this value is added to the time at which the projectile leaves the muzzle:

Extending the original curve until it is tangent at this point gives the complete free bolt momentum curve shown in fig. 1-13.

This curve can be used directly to determine the bolt weight necessary to limit the bolt velocity to a safe value over a given interval of time. By integrating under the curve for the desired time interval and then dividing the result by the time interval, the average bolt momentum for the interval can be found. Dividing this average momentum by the allowable average velocity for the interval will give the required bolt mass. That is to say:

P(MrVrt)

A simple and sufficiently accurate method of evaluating the integral in equation 1-4 is to measure the area under the curve by use of the so-called trapezoidal rule or some other method of approximate integration such as Simpson's rule.

Now assume that the cartridge case is not lubri-cateel. As previously explained, this condition re

point of tangency (.00826 sec)

Figure 1-13.

.010 time (sec) Free Bolt Momentum for First 0.010 Second.

Figure 1-13.

.010 time (sec) Free Bolt Momentum for First 0.010 Second.

point of tangency (.00826 sec)

0 0

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