About the 'Pump Assist' Modification for Benjamin Airguns
 

The Pump Assist is a modification to a factory Benjamin 397 and
392. The standard pumping linkages are removed and replaced by
an advanced mechanism that flattens the force across the pump
stroke for all 8 pumps. The front lower cylinder is slightly modified
to accept the pumping mechanism as is the wooden pump arm
stock, but the remained of the airgun is untouched.

Below is a picture of a standard Benjamin (top) and a Pump Assist
modified Benjamin (bottom) in the closed position. The only
noticeable differences are the pivot lug brazed onto the cylinder
(halfway between the forearm stock end and the barrel end) and
the wooden pump arm stock is moved rearward less than 1 inch.

The next image shows the standard Benjamin and a Pump Assist
modified Benjamin in the fully opened position. Here you can see the
multiple linkages associated with the modification. To assure the
quality and longevity of the Pump Assist modification, the load
bearing linkages and pins are produced from aircraft grade
Chrome-Moly alloy steel.

Warning: The Pump Assist mechanism was designed to safely
support 8 pumps only. Exceeding 8 pumps may cause
permanent damage or premature failure of the mechanism.