This step is not covered in the instructions, except for a small illustration on the first page "Parts" drawing.
TIP: Don't separate the nose cone end first. You'll have more control, and more to hold on to, if you cut from the back and move forward. Cut off the rear ring first.
TIP: Notice the knife tip placement in the wide notch. The blade is set to the right side. The notches are wider than the blade. When you cut to one side you'll have less to clean up and remove later.