A rifle barrel sit until you start to see pitting? I have two rifles I have neglected to shoot that have been in the safe for 5 yrs and 10 yrs respectively. Both were put away clean and don't show any signs of major exterior issues but is there any opinion short of a bore scope?
Tons of variables would come into play here........humidity, where they are stored, how they are stored, oil in bore, etc, etc. There have been countless rifles sit for 50+ years with no pitting though. Its all in how they are kept.
Obviously nothing will be beat a bore scope. but you'd be surprised how much you can actually see, especially something like pitting, if you get a light small enough that can fit inside the chamber. for years I've had this cheap little light like the one below but from Academy and I use it all the time and when you put it through the open chamber end and look down the muzzle, then you can see alot. You just have to move the light around so you don't always get the full shine power, then you can see alot of the barrel ID. you make a u like in the pic and you can move it around to see different parts of the barrel.