That sort of thing never became "mainstream". Very low powered BB guns (eg "Red Ryder") and careless play with them was very mainstream. We've gone from air rifles being serious weapons (Lewis and Clark) to air guns being toys (the smoothbore RR) to air rifles being serious weapons again (see Cabela's or even Wal*Mart).
Girandonis fired a ball from (roughly) 150 to 200 grains at about 800 fps. So power-wise, it was neck-and-neck with a standard velocity .38 Special.
Which is A TON more power than a "very low powered BB guns."