For no apparent reason I found myself thinking about Belleville washers this afternoon .... yes, sad, I know.
I seem to remember that the single stroke pneumatic that made it to prototype form a few years ago (sorry, the name escapes me at present) used Bellevilles in its design but I do not know where, except that I think the washers were used to provide a compression/expansion force somehow.
This then led me to wonder if anyone had ever tried a combination of a coil spring with a gas ram powered piston. Would a spring inside the ram offer any advantage; or indeed would a spring outside the ram around a piston rod offer any advantage? Would the gas ram propel the piston a tad faster than the spring such that the spring 'powered out' a fraction of a second later and eliminate any piston bounce, if present?

Just musings in senior moments. Most likely complete and utter tosh.
Cheers, Phil