If the projectile has some free run prior to engaging the rifling (e.g. from forcing cone erosion), you can assess the effect of this on the Resistance Pressure vs. Travel by making an entry to the Projectile Free Travel input slot and re-clicking on the ReCalculate Resistance Profile button.

In this example, we will estimate that the rotating band travels 2.00mm prior to the rifling interface. Once you have pressed the ReCalculate Resistance Profile button, your screen will look like the screen below.

An entry to the Projectile Free Travel input slot along with clicking on the ReCalculate Resistance Profile button will cause the program to modify the resistance pressure vs. travel as shown in the figure above, and cause the rotating band calculations to assume there is a travel delay in rotating band contact with the rifling. For projectiles fired in barrels other than full gain twist (those with a zero degree starting angle), a spike in the torque vs. time/travel profile will be seen. The implications of significant projectile free run prior to the rotating band engaging the rifling will be addressed on the following page.

All of the basic inputs are set so it is a good time to once again save your projectile.

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