The rules for smallbore rimfire silhouette say you can't use "stingers," which, unfortunately, are not defined.
Per the web: the popular Wolf 40 grain match grade target ammo is 1050 FPS, i.e. subsonic.
Other, "high velocity" ammunition from CCI (mini mag), federal, and winchester is 40 grain, 1235 to 1260 FPS.
Is the high velocity ammunition legal for smallbore competition?