Of course they work. One large volume spring air rifle manufacturer used them on piston heads for all of their models for a considerable number of years. Different power outputs over the range of guns. They used big and small transfer ports
Absolutely
I have 8 AA Sidelever Springers from the 1980s all of which run very nicely on O rings
But there are people who vehemently insist that they are out of date and should not be "revisted"
Can you believe it?
Matty
Opportunity is missed by most people, because it is dressed in overalls and looks like work.