fillers, SEEs, rings, etc.
This thread is coverin' it all.
I don't see how low density filler like < 1 gr of loose dacron used in front of relatively fast powder has or could have much to do with chamber or barrel rings. However, given the wide variety of odd components that are concocted by shade tree ballisticians... never say never :)
No more than a couple of years ago an acquaintance told me with absolute certainty that he doesn't use dacron filler because it "will leave a bunch of melted plastic in the bore". No doubt, he heard it from a reliable source who heard it from a reliable source who heard it somewhere?
SEEs are nearly impossible to prove, demo on purpose or disprove. That's why anyone who says they can prove that it doesn't happen by loading some undercharge of slow powder then firing it without consequence proves nothing!
There have been enough instances of undercharge - slow powder blow-ups that it seems almost certain these types of SEEs do happen.
In certain applications/loads it's interesting to note the print-outs of raw pressure trace data. Everytime I see one that does show the multiple pressure spike events it gives me the willies!!! I pay very close attention to those and try to avoid similar load specs.
I don't know how many dogknoted 22 rf barrels I've seen. It must be pretty common. The little 22s have been around for a long time. Over the years much of the 22rf ammo has had a bad reputation for being unreliable. Easy to re-create the events. Load up the ole 22 with who knows what ammo. Fire, fire, no fire (must of not fed another round), fire... ring! What's also interesting is it is not unknown that 22s have been taken to gunsmiths for repair that have multiple 22 slugs still in the barrel :)