ive never, ever seen copper fouling in a bore from a NEW gun....
not to say one couldnt slip through....but other key places to look...magazine (brass rubs off often times) feed ramp, bolt face, bolt etc...
i carry a flashlight...hard to inspect a gun without one if you cant break it down...
the shop owner told me my 7600 i just bought was new...it looked new but ive seen 50yo guns look new too...but i had to run the flashlight over it...he looked at me like i was nuts....but i determined it was new...key give away is usually factory grease in the action and such...and no fouling anywhere..
also, without a box and manual and everything that is supposed to be in that box, i will not pay NEW prices...thats the thing about buying a new gun...you can go down the road and get the same gun for right about the same price...its easy to pass off a really clean gun as new...i could still sell my 7600 as NIB...but ive had over 50rds through her...only thing that might get me is my base might have put marks on the reciever...
gotta be careful when buying guns...they dont have an odometer like a car..