Originally Posted by ChattanoogaPhil

I'd chose a reliable round with higher velocity than typical HV ammo... something like CCI Stinger IF they feed well in your rifle, or Aguila as mentioned earlier... but whatever you chose RELIABILTY is the first priority. IMO, rimfire reliability to feed and fire is more of an issue than anything else.

Below is a link to some data on .22lr compared to other handgun rounds.

As was mentioned earlier, 60% of the time an attacker was immediately incapacitated with one shot from a .22lr handgun, which is on par or slightly better than other handgun ammo in the report. My guess is that a .22 rifle with higher velocity would yield even better results. According to the data, the significant shortcoming of the .22lr compared to others is that if you don't incapacitate the bad guy on the first shot then that's about it... 31% of the time the bad guy is never incapacitated. Most all other handgun ammo failed to incapacitate the bad guy only 10-15% of the time.

An Alternate Look at Handgun Stopping Power