Quote Originally Posted by Geezer View Post
A real possibility already. Outside the U.K., with the long-established 12 ft-lbs limit.

Setting aside the historical precedents (Girandoni etc) in 1979, a top power air rifle made 11-15.

1980, the HW80 was gusting 20.

1990s, the Patriot, Eliminator and modern PCPs were hitting 30 ft-lbs in .22” and .25”.

Now, there is stuff out there in .357” and .45” making as much as 500 ft-lbs.

At some point, in unrestricted jurisdictions:

A) a criminal will kill someone with an air rifle that makes more power than a 9mm or 45ACP;
B) a mass-shooting nutter will do the same, just more than once;
C) pressure groups/politicians/media will discover that “BB guns” now make more power than a 45ACP. Especially if the next step in development involves magazine repeaters, real or fake semi-auto, etc.
Some eejit will ruin it no doubt one way or the other.
Airguns still fall in the same bracket as crossbows at the moment and one needs a certain amount of braincells and skill to use them.

They put black powder revolvers on licence ages ago here because someone got it in their head to rob and kill a taxi driver with one.
They did the same thing with 'hunting firearms (smooth and rifled) because someone walked in to a gun shop and bought one 30/30 lever action legally and shot 3 people, 2 of them died. This was 2006.
The latest one is the licencing of magazines, smartly licencing all deactivated weapons because terrorists could buy ak magazines too freely.

Your mass shooter isn't very likely to lug his scuba tank with external regulator with him when he can obtain almost anything he wants on the black market at present.
Never say never.