The .22 LR shot ctg. that was available here in the USA/Canada, used #12 shot.
One of the gun writers some decades ago, wrote an article on using a .22LR with shot for practicing wing shooting, by shooting dragon flies at a pond. In the article, he (?) noted the best range for this type of shooting was just a couple yards.
I would think one of the new Bug A Salt guns would have just as long a range & be cheaper to shoot.
Of course, these would not be lethal on mice, but are lethal on insects - this I know from experience.

https://www.google.com/search?client=firefox-b-1-d&q=Bug+A+Salt+Guns