38mm6XL J520 failure

Anyone have recent experiences with the 38mm6XL skidmark, J520?

At Reno last week one did some real damage to electronics when it blew out the forward end upon ignition. My gut feeling was it looked exactly like someone forgot a spacer, but obviously being a 6XL motor that was not the issue. I looked over and it definitely was not a forgotten casing. Field analysis did not yield much either. Any guesses?

Used a non standard igniter? [other than the 1 that came with it, could cause over-pressurization & a boom-boom]

I flew 2 of them in may no issues.

With out pictures or detailed info.....just guesses.

I had one cato a few years ago, taking out one of my best rockets.

Yes, this is mostly guesswork. I wanted to see if it was a known problem child but it sounds like not.

Jim, bummer! This was a nice one too.

I have heard that one should tighten the nozzle case connection only tight and not force it any further and or back it off a little after tight. This is just hearsay, but I heard it from a guy who deals in engines.

Guessing here, but I don't think it was seated properly. The threads on the rear closure are not strong enough to drive the liner into the case. If it's not seated all the way when you thread it in, you'll just strip them.

The OP stated it blew the forward end of the case , so stripped threads or liner failure are out . Has the case flown before ?