Originally created by a member from the team Navarone, a then Line SI sponsored team. You can see the similarities between the "Top Gun" and the SI Bushamster.
The Top Gun was held together by ball detents, called the "Fastlock" system, and was the first to do so, though not perfect. The gun had the habit of coming apart in the field. The field strip idea, was just a little too good.
The gun was good quality, but was being released just as the first semi's were making their way into the main stream. ( Semi's being the 68 Special, and PMI-III - aka VM-68 ) Therefore not many were sold, making this a great collectors item.