I have a Benjamin model 397, purchased new in the early '90s; I like the gun. Many people have complained about the difficulty of pumping them up. My problem, however, is the extremely strong spring on the bolt. A few pellets loaded, and my fingers get very sore. Is there any way to reduce the strength of that spring. Why is it so strong? Does the firing pin impact have to propel the pellet past where the compressed air gets behind it?
I have recently acquired a squirrel problem; they raid my bird feeder. I don't really want to kill them, just to give them a good hard sting. So I only give the Benjamin 3 pumps. If I wanted to kill them, I would use a Marlin .22, firing quiet CB caps. Thanks for any helpful suggestions.

Melvin, welcome to the 'fire!

I'm no expert and don't know the proper terms but I'll try.
There is a pin on the bottom of the bolt that reaches inside the action. When you "cock" the rifle, the pin on the bottom of the bolt slides an internal cylinder to the rear so it can be held against spring pressure till you release it by trigger.
Squeeze the trigger and that captured cylinder bumps forward hitting the valve and releasing the air pressure to the barrel/pellet.
The spring pressure is not adjustable.

A piece of leather the size of a 50cent piece to put against the bolt for cocking may help..
Good luck!

Ya ain't gonna train them. Feed 'em or kill 'em. If you want some entertainment, get a Twirl-a-Squirrel.

It's the air valve that is struck to release the burst of air. And yes, that spring is quite stiff, as is the trigger.
I have not found any tips for lightening the bolt pull. I just make sure to put a drop of oil on it once and a while and I put some moly paste on the trigger and sear. The gun shoots well in spite of the stiffness, it's my favorite for pellets.