Self loading rifled CO2 pistols?

[wobbly bob]

So the striker/hammer is cocked by the blowback, but the trigger rotates the magazine?

Correct. Semi-auto pistols, that is to say those that chamber the next shot by putting it into the breech, are illegal in the UK

The Crosman, Steyr, and Drulov escape the ban because the pellets fire from the magazine not the breech

A highly technical point, that has caused controversy, because in effect they act as semi-auto

And very nice they are too