Sadly I have had it happen to me on a bolty, in my CA m24 to be exact.
IIRC it was all shooting fine then suddenly after firing off a shot the bolt pull got a little slack and not as stiff when I cocked it, I then fired it and the bb acted as if it had been made of lead, cocked it again then the snapped section of spring got jammed between the piston and cylinder side scratching the crap out of it, luckily after the O ring reached its maximum travel.
I put it down to old age and metal fatigue :shrug:
Yeah I had no damage lucky. I think the cold might have something to do with it tho. Already put a lighter spring in it. Going to try and get some testing done with the lighter spring tomorrow. I don't think I will be getting a 190 again.
I have had a spring break, but it was too long and so the constant fatigue wore it down. It was also in backwards (variable pitch). Anyway, now I cut all my springs just one or two coils so that that doesn't happen.