You can use Activation/Deactivation method to activate/deactivate Euler parts to speed up the calculation. First, estimate the length of the fully extended jet (L). Divide the mesh along the axis of symmetry into parts each length 1.5*L, then join all parts and verify the joins. Deactivate all parts except one in front of the jet, based on the average velocity of the jet, estimate the duration of time required for the jet tip to reach about half way into the first part, and run the calculation for that duration of time. Activate the next part and restart the problem to run until the jet tip reaches about half way into the next part. Repeat the process until the jet perforates the target. If appropriate, deactivate the part behind the jet. While this may be a little more labor intensive, it could speed up the total calculation time required by a factor of 3 to 5.