Yep. 22LR shot shell.This is my 22LR rat shot.
Is this what you meant by rat shot? I have some of that as well but almost never use it. The pattern is far too wide but it does work well for keeping the neighbor's unwanted dogs away.
I've never used it before. Years ago my dad used 16 gauge #8 birdshot on what we used to call a wharf rat.
One had taken up residence in my parents home that I grew up in. This one would make three inch diameter rat holes in the baseboard.
I woke up 6:30 one morning to the sound of his 16 gauge shotgun going off downstairs in the living room. My dad killed one that he had cornered. I also found out that prior to him shooting it that my sister had the bright idea of throwing the family cat at it. The rat looked at the cat and the cat looked at the rat and the cat ran away in fear for it's life.
22LR shot in this case would only pissed off the rat. Just the tail on that rat measured around 10-12" long.
The good thing after the rat's demise was that my socks didn't go missing anymore.