When I worked in a gun shoppe, we used to get guys that went shooting "once in a blue moon", they'd come in with their pride and joy that had been sitting in the cupboard for months, the pre-storage treatment was WD-40/RP-7/CRC .
The poor rifle would be gummed up tight as a
That wasn't too bad, you could normally free up the action with a good soak in turps or diesel.
The real worry was Greek or Italian blokes who had LIBERALLY applied olive oil!
Once the volatile bits of olive oil have evaporated what you're left with looks and behaves like epoxy!!
I had to boil a semi-auto .22 every day for nearly 2 weeks before I could get the thing apart!