There are a handful of situations where a symbol can do more than one thing / get used without getting used up...
- Channeling in Reckless Stance
- "Measure Twice, Cut Once" Talent
- "Frenzied" Condition
- A couple special rolls in various adventures, like TEW's traveling rules if memory serves correctly.
- Probably some other cards that are escaping me right now - you might check the miscasts, the locations, and maybe the Hedge or Dark Magic rules
The all say something like "in addition to the usual effects of rolling that symbol". If something is meant to not use up the chaos stars, it uses language like that. It's usually really called out in unmistakeable language.
Now look at the text of the description for Unreliable... notice where it says "This is in addition to any other effects." That's not as crystal clear as it could be, but it is close to the wording in the examples above. So, sadly, it seems that guns will technically explode without using up the chaos stars. Yuck. They were bad enough without that. Don't know why FFG has so much hate for guns. Pay 5 to 10 times as much with the only benefit being 1 point of pierce, and it can also blow up in your face! Sad.