Originally Posted by nosaj
Or if it is just a rough edge on the bore lining will it wear in with use? Or just mess with accuracy from the beginning
Chrome lined barrels are not really sought after for their accuracy. Sure they are combat accurate enough but I doubt you will ever find a bench rest shooter with a chrome lined barrel. The reason for the chrome lining is to reduce the likelihood of rust within the chamber and bore thus improving reliability.
Could it be chrome from the barrel flaking off? Yes, maybe.
Could it be metal shavings/burs left over from the manufacturing process? Possibly.
Could it be pieces of your cleaning rod abrading off? yes (assuming your cleaning rod is a polished aluminum).
Could it be "lapping" from the bolt and barrel extension?
So many possibilities. My suggestion is take it to a gunsmith with a bore scope who can inspect the bore. You should inspect your cleaning rod thoroughly and perhaps use a different cleaning rod to see if this still happens or if the shavings are a different color.
Also inspect the bolt closely and see if there is any unusual wear on the bolt.
Pics might be able to help us identify what you're looking at.
What kind of ammo are you shooting?
Are you able to remove ALL the shavings when cleaning and if so have you shot the rifle again and did the shavings come back?