The CB Longs and CB shorts from CCI should both be using 29 grain bullets at about 700 fps (in the CCI rifle test barrel). Subsonics should be using a 40 grain bullets at 1050 fps.
Thats my understanding also..I believe the CB longs will usually feed better out of a standard box mag, as the shorts tend to pop out before the bullet tip is properly supported/guided by the "feed ramp"...