KS with guns is different than KS if you bomb a friendly. In fact, and I can't find the exact 'readme' release this was in, but I believe you can bomb near a friendly and not KS your self. Friendly bombs will not KS a bomber or damage a boombee.
EDIT- Found it, way back in Nov 2004 with release 2.01. It says:
"Killshooter is no longer triggered from bombs or rockets."