I have a STEALTH Billet Upper LT007 with M4 cuts that I purchased from a authorized Larue dealer.No matter what type of cleaning protective I use on it after it sits in my safe 2 or 3 days it has a white dull discoloration in the general area where the BCG fits into the upper. I own a complete 18" and 16" stealth upper and have no problem with either one of these.This upper was also has a super tight on my lower,but you will not hear me complain about a upper and lower that fit with no slop what so ever. Any ideas on my dull finish??
Edit "I have used Machine Gunners Lube"