CCI Quiet .22 subsonic long rifle ammo is airgun quiet, maybe quieter and shoots pretty good groups at 50 yards and a 40 grain .22 bullet with a BC of about .13 drifts a lot less in a crosswind than any air rifle pellet.
fifty yard group
Yea, I know it isn't an air rifle but in most places where it's illegal to discharge a firearm, it's just as illegal to discharge an air rifle.