Crosman 2240 or 2250

[David22]

I've seen mixed posts on this, and there doesn't seem to be a definitive answer
I've got a stock Crosman 2240 and was tempted to dabble in modifications given the huge range of custom parts available but wouldn't want to create an illegal weapon which (I'd assume) is a real possibility as the stock 2240 in .22 must be close to 6ftlbs out if the box ?

Is it safer to use a 2250 (classified as a rifle) or is it the presence of the stock that makes a pistol into a rifle ? Is a 2250 with grips a pistol ?

What makes a pistol a pistol ? I can't find a decent definition. Surely it's about the overall length of the weapon ? Confused