There is a .22rf 'shot-shell' that is pretty good for shooting rats or pigeons inside sheds.
It works well in a smoothbore .22 or a rifled barrel.
The Rimfire Report: .22lr Shotshells - Are they worth it? | thefirearmblog.com
If the fancy takes me, I'll walk down to the stables and wait for the straw to start moving and rustling.
The last ones I bought were gbp £10 per box