The BNC-55AC nose cone is bit different. It's the same nose cone used in the Estes Arcas kit.
You can check it out on the Semroc website or in the Jim Z instructions.
Instead of being a standard ogive shape -
Right above the shoulder is a slight dip in the diameter. Be careful not to sand this down or sand it off. That slight concave dip is supposed to be there.
The nose cone tip is rounded off.
It's really an elegant, subtle change.
Here's the strangest combination picture I've ever posted.
(One hand has to hold the camera!)
You should lightly sand down the grinding marks before filling the nose cone grain.
The left thumb acts as a bumper to prevent you from sanding over and removing some of the raised lip.
My left hand thumb is held right up to the raised shoulder lip.
The right thumb does the up and down sanding and stops at the left thumb.
If you do this correctly, you sand down until the side of your right thumb hits the left thumb stopping the sandpaper before it can reduce the shoulder lip.
After you've sanded the sides of the nose cone, pull it slightly out of the body tube.
To clean up the joint a bit more, fold a piece of 400 grit sandpaper in half.
Run the folded sandpaper gently along the down the open joint.
Go lightly, you are just knocking off any uneven edges on the nose cone shoulder.
On the right side, You can still see the brush marks.
First sand the flat sides of the fins first with 220 or 320 grit, knocking off the high brush mark lines. After that, sand smooth with 400 grit.
BUILD TIME (Nose Cone Sand, Balsa and Tube Seam Fill and Sand, Sand Balsa and Tubes = 1hour, 15 minutes
TOTAL BUILD TIME so far = 2 hours, 30 minutes