there are a select few who have done this.
it's far more involved than simply swapping barrels. you need to move the trigger group back in the reciever to make room for the magnum magazine, hence you also need to modify the inletting in the stock. spring rates also need to be addressed for this conversion to function anywhere near properly.
my biggest problem with doing it is as follows. 10/22s use an aluminum reciever, where as the 10/22M uses a steel reciever. my strong opinion is that there was a very distinct reason that ruger saw fit to use steel for the magnum round, but aluminum was sufficient for the LR round.
if you are interested (i wouldn't sugget it either!), look up rimfire central, there was a writeup done by one of the members there.
PS: i really hate refering people elsewhere, but it's nessecery sometimes!