No witness marks that I could see. I tried 4 more bolts (2 Colt, another BCM, and a NiB from St. Croix Tactical) and all seated fully in the carrier with minimal force after I removed the gas rings. I tried measuring some of the diameters on the different bolts (bolt tail and various points on the body) but my calipers don't have the necessary precision to notice a difference in the dimensions.
The suspect BCM bolt will seat all the way after some cycle of the PSA bolt through the carrier. I assembled the BCM bolt in the E-carrier and hand cycled it in my upper. There is definitely more resistance during cycling of the firearm with the tight BCM bolt than when the PSA one was installed. I THINK the resistance is coming when the bolt tail is starting to enter the channel it rides in during operation. There appeared to be enough clearance (~.003") for the main body of the bolt.
BCM bolt installed until resistance is met:
PSA bolt installed and fully seated for comparison:
After going through all of the bolts I ended up installing the other BCM (one that fit) in the E-Carrier and will try running that for a while.
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