Used Estes C6-3; and it rose up beautifully. Ya scallywag!  Arced over a bit and after apogee t' charge blew t' rocket apart.  I had made sure with a poke test that t' parachute wasn't too tight, ya bilge rat, but t' charge made t' rocket come down in 5 pieces (nose, me hearties, parachute, body, motor, motor retainin' ring). Avast!  I think it was a certain lot o' C6s I had (from Estes Blast Off Flight Pack) with too much ejection charge.  Broke a body fin on landing, but will fly again...maybe after some modifications.