Roller,
The spring is only bent enough to assist the ejection, .010 - .030? It should only add a minimum amount of pressure to the cranking. I do not think it will be felt. The idea is to pop the shell out of the chamber as the ejector starts the return movement. The spring is of minimum thickness, .015 - .030 ? I have not tested this. I am trying to locate spring steel shim material. I did not know it was so expensive.
Google search says the impact devices for packages are called acelorometers. They are inexpensive but the equipment they attach to is not.
A digital force meter that will do just what I want is $400 and much more. Still looking.