Now, if you'll forgive me, one doesn't like to admit these sort of things: I was going through the gun cabinet this morning and I picked up my SMLE rifle. Something caught my eye. In the grooves of the rifling there was... rust.

This shocked me, good sirs and ladies, shocked I say. I clean my rifles and the bore of the SMLE is shiner than a new shiny thing from Shiny Town.
So. Two options present themselves: 1) PANIC, or 2) possibly accept that the barrel is 90+ years old and curse myself for a overly judgemental fool.
Does one need to worry?