Many years ago I bought a BCM upper that has sat unused. As I try to manually retract the bolt carrier it is “sticky” for the first bit of travel during what I would guess is the portion of travel related to the unlocking of the bolt after that it feels normal. Multiple bolt carriers and bolts exhibited the same behavior although I believe to varying degrees. At first it seemed the gas tube was sitting slightly askew and I thought that might have been the issue so I tightened the barrel nut a smidge. That seemed to fix the apparent off set in the gas tube. The stickiness improved little if any. I notice a bright spot around the front edge of the notch in the upper receiver for the cam pin but that seems common to my other AR that functions just fine. I see some minor machine type marking and a tiny bright spot on the bottom face of the 9 and 10 o’clock “lugs” of the barrel extension. Anyone have any recommendations on a fix? Shoot it and it will break in? Needs a new barrel\extension? Some sort of upper receiver defect and it needs a new upper receiver? I have yet to fire a round through it to know if it impedes function but it is definitely harder to manually retract the bolt compared to any other AR I have handled. Not impossible but harder than normal. Thanks for any input.