Well, Im a few days too late to have seen this thread. Flew a CTI K260 long burn this past weekend. Everything looked nominal with the flight. Recovered and returned to camp only to find I couldnt pull my 6 grain case out of the rocket. Removed the rear closure and slid it out from the top to find a substantial bulge in the case between 1-2 from the end. Sorry, no pics. Vendor swapped me out immediately on the spot.
One, I feel lucky nothing blew. Two, Im happy this didnt happen in the other rocket I had that can fit long 54s.... it has a zipperless coupler. Would have had to cut it out. A fellow flyer saw the bulged case and mentioned he had read about this problem on the forum and also mentioned using epoxy to glue in the forward closure. I havent flown many 4+ grain 54s yet. Glad I know about this now!