The .22LR shot load was developed in the 1950s by Mossberg and was followed by the production of smoothbored .22s by them and Remington, perhaps a few other makers as well. The idea was for an inexpensive means of practicing wingshooting.
I have an old Guns and Ammo edition that dealt exclusively with the .22 rimfire, in which it reviews one of the smoothbore Remington pump guns. It showed a picture of a pop can riddled with pellets from a shot taken at 30 feet. It would not surprise me if it would have been able to break a clay at that distance, but the article did not say if it could. A few years ago Marlin teemed up with CCI to revive the idea by creating a smoothbore .22mag for pest control use. I have no idea where that experiment landed, though it is worth noting that they tried the magnum chambering in order to increase the pellet count.
On an interesting aside note, I once years ago chatted up a taxi cab driver on my way from Barrie to CFB Borden who explained how he lost his right to own firearms. Apparently his ex-wife's new boyfriend or husband threatened to take away all of his custody rights to his daughter, after which he took a .22 rifle, cut down its barrel to diminish the velocity, confronted the man and shot him in his privy area. Please kids, do not try this at home!
With Regards,
Frank