There was no outward sign of damage, however after the initial incident every spent case (factory included) got stuck in the chamber & had to be pounded out. I don't have my notes on hand at the moment however I recall measuring the empty case from that first FTX-loaded round & found that it had expanded by as much as .005 near the base and expanded the primer pocket as well when the primer was blown out of the case, and the web of all subsequently fired cases were a couple thousandths wider than previously fired cases as well.
I believe the 'bulge' is towards the rear of the chamber pretty much right where the extractor groove is cut out, as that seems to be where the majority of the case head enlargement was taking place; I'd also expect that to be the weakest section.
I don't consider myself an expert by any means, so it is entirely possible that there is some other factor at play here that I haven't yet considered. As you might imagine, I spent considerable time after-the-fact trying to recreate the events leading up to that incident to determine why it happened, but was ultimately unable to identify any other viable explanation. I can't completely rule out the possibility that that particular round somehow received additional powder through bridging or something (they were loaded on a Lee turret press using the auto-disk powder measure), but I do not think that is the case.
I still have the original barrel on the off-chance that more information could be gleaned from an 'autopsy', or that it could possibly be salvaged for some other use, but after confirming that the issue no longer occurred with a new barrel in place, I ultimately decided to chalk it up to user error & relate my experience to others as a cautionary tale.
