I will send you an email with the impromptu video I recently did. I have never made one on YouTube, so what you may have seen is not mine.
The Mod 220 was indeed a first in many ways.
The fixed barrel/sliding cylinder arrangement along with the (then) novel approach to mechanically reduce recoil by having a built-in pneumatic damper with the mainspring made up of two uneven lengths, was very hi-tech at the time.
Other stuff like the self adjusting spring guide, a superb modular trigger and a selfactuating pellet ramp to help the user guide the pellet exactly into the barrel were the cherries on the cake.
David.