The Girandoni shot a ~400gr bullet at 1000fps, which is....higher!!! 850+
Incorrect.... It used a round ball which in .46 cal weighs 144 gr.... That is ~320 FPE....
More than point out how little "progress" has been made.... it realistically shows the limits to airguns imposed by the laws of physics.... which haven't changed in the last 4 centuries eith ...