I’m sure that has been done.

This was Jim Tyler’s explanation, though without quantifying how much more efficient a springer is, but suggesting that it’s not all down to heat:

https://www.airgunshooting.co.uk/exp...work-1-5181958

For what it’s worth, a back of an envelope calculation based on the cocking/pumping effort figures in Tom Gaylord’s blog suggests that a typical 12-14 ft-lbs springer requires 30-40 lbs (equivalent) to cock, whereas pumping a Sheridan up to achieve similar power needs more than 200lbs of effort.