How did you get 0.09 s for the time in the barrel? That seems too long.
What was the exit velocity?
What drag force are you using after the pressure on the back is gone?
What are your analysis settings for Initial, Minimum and Maximum Time increment for each step?
To save time, you could create a new Rigid Dynamics analysis with just one step. Apply an Initial Velocity to the bullet equal to the exit velocity and have the Standard Earth Gravity and the drag force. You can use a large Maximum Time increment to allow it to solve in a smaller number of time steps.
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