How it works:


When pumping a standard Benjamin, the user exerts almost no
effort over the first 2/3rds of the stroke and than the force required
climbs to a maximum near the end of stroke. The Pump Assist
mechanism allows the user to apply a small and relatively constant
force to the handle over the entire range of the pump stroke. The
work required for both pumps is the same, but the peak force of the
Pump Assist is significantly reduced.
The Pump Assist action is so smooth and effortless that the airgun
can be easily cocked holding the pistol grip; this allows the use of a
range-finder scope. Benjamin's are notorious for their excellent
accuracy and repeatable velocity; the ability to use a real scope
turns your low cost Benjamin into a precision airgun.

The red line in the graph below shows the handle force for a factory
Benjamin starting with the pump open to the right at 120 degrees and
closing to the left.  The force peaks at 34 lbs, than the force drops and
the pump abruptly closes. Note there is little force (or work) over the
first 80 degrees arc, than the force raises sharply and drops.

The blue line in the graph shows the same Benjamin with the Pump
Assist modification. Note the force rises almost immediately to 13
lbs and is flat until the force drops off. A clutch mechanism releases
the tension to the handle so the handle closes gently. The constant
force and gentle closing create a remarkably smooth pumping
motion.

The graph below shows the peak force per stroke for a factory
Benjamin (blue bars) contrasted with a Pump Assist Modification.