Definitely a load of flannel….
To be fair ‘Air rifle headquarters’ was an American catalogue written by Ian Law, I think he was trying to convince Americans of the advantage of airguns over firearms, in comparison they probably were a bit quieter. Nothing to do with the ‘delayed recoil’ though…He mentions the ‘virtual silence’ of airguns a lot actually, as well as the accuracy and also the revelation that they don’t produce any smoke!
Matt