Apropos of nothing - since you're looking for a .22 - but back when 'Fast Draw' and 'Walk and Draw' were popular - one of the most-often used 'guns' was a 'Crosman .45' - a pellet gun.
It was full-sized, and the compressed air blast was enough to stop a timer.
You can still find these - even the predecessor made by 'P.Y.Hahn', since Crosman was somewhat loathe to put their name on it - and if the valve assembly's still good, they make a good trainer.
Vaya,
Scouts Out!