Sub sonic 22 LR cartridge

"Standard velocity" in .22 rimfire is 3 grain black powder equivalent from a .22 Short with 29gr bullet or 5 grain black powder equivalant from a .22 Long with 29 grain bullet or .22 Long Rifle with 40 grain bullet. All those end up just below the speed of sound. Technically subsonic.

CCI CB Short and CB long are 29 grain bullet at 720 fps or 33 foot/pounds impact energy.
CCI .22 Quiet is a 40 grain bullet at 710 fps or 44 foot/pounds impact energy.
Aguila .22 Sub Sonic Sniper is a 60 grain bullet at 920 to 950 fps for about 120 foot/pounds impact energy -- more than most .22 LR standard target rounds (40gr at 1,080 fps = 104 ft/lbs).

Sub Sonic does not mean CeeBee or Colibri. Sub Sonic means below the speed of sound. The CB and Colibri rounds are more like the old Zimmerpatrone (indoor cartridges) for short range target practice or small pest control.

I can stop CB or Colibri rounds in the backstop I use for my pneumatic .177 pump-up air rifle for indoor practice. A lot of subsonic.22 rounds would not be safe with that level of backstop.

Cci subsonic are kinda loud out of my sons wrangler. But he has a blast. And saves on the hearing aids later in life. Doubled up ear protection and they are still loud for what they are.

I carry a taurus 94 snub around the homestead and always in my pocket is a pair of Sonic II hearing protectors which allow you to hear any of the noises on your walk but will block high decibel noises like gunshots. that way you could just carry your regular .22lr rounds in your SP101.

CCI CB-Longs are what I use when I need a 22 shot to be as quiet as I can make it. For pine cones and tin cans they work great. I found them lacking for anything the size of a coon for reliable stopping power so I would not use them on 10+ pound animals. I saw some at the last couple of shows I was at.