I think there is enough info here that you know what happened, maybe not exactly how. So where to go from here?
Not trying to throw gas on the fire here John, your a smart guy and I know you tested like crazy, I remember following your entire L3 build. But others can learn from all of our mishaps.
Not saying you do this but I continually see people test Ejection charges here on this forum 1.0 gram then that doesn't work, 1.1 he no
Love, 1.2 - hey that worked so I'll but a little extra 1.3 gram in there. That is pissing in a bathtub. Unless this is a small rocket (2.5" and below) I've been told to work in increments of .5 gram only and your backup needs to be a significant increase from your primary. On my L3 rocket I had to hone both AV connections because it would
Slide in fine but had to work on getting it out. After a significant hone - it felt so smooth and still had a good fit- so I tested at 4.5 and 5 - both separated. However in talking to my TAP and others that had much experience with the same rocket " blow it out or blow it *** jokingly kept coming up. Then a friend said he had a 6 gram charge not separate the payload and his 7 gr backup did the trick - so he now is at 7 primary and 8 backup - with a long harness and 15-20 flights on the rocket. Of course this is FG and non piston long harness setup. I took his advice on my L3 even though I tested at lower charges. That laundry has got to come out in our hobby, too dangerous otherwise.
Big Charges: So I went a little higher on my phenolic and cardboard rocket - not a long enough harness - this stressed the NC bulk head and on my phenolic it split the end of my booster tube. So in conclusion just increasing your charge without planning for it is not the best option based on my experience. So IMO the important factors of using strong charges are; The type of tubing material can withstand, relief holes, smooth connection even if you have to hone and long harness.
There is nothing worse than watching a rocket come down ballistic and knowing everything is armed but obviously will happen to all of us and we hope and pray no one is in the area. "What the freak just happened??!" Aww crap (or other expletives). Heck if I lost my L3 I'd probably walk away for awhile as I know I've got $2600 and 4 months wrapped up in it (of course many on the forum have much more $ and time wrapped up in theirs). CJ might chime in here, when I was crying about my ballistic L1 rocket from a stuck coupler he wrote me a little story about an experience he had at black rock with a very expensive rocket didn't make mine hurt as bad. At LDRS 34 man I saw some big CATOS and thought oh man these guys and gals got to be sick! No matter how expensive they all hurt.
One way to get over it is to enjoy building another monster on the rebound
. I look forward to following that build thread.