This has been covered before...do a search for pictures of the wear areas.I think the last person to ask had a BCM upper if that helps.
Yeap...normal to me and is very common in my experience.Every upper I have has that spot of wear.Its just the carrier making a home for itself.Once that sharp edge develops somewhat of a radius the wear will stop.
In fact after a bit of use you will probably also see some wear in the charging handle channel at the rear edge of the cam pin recess from the cam pin bearing against the receiver on its foward cycle into battery.It will radius the sharp edge also in making itself a home.
You will also see the carrier rails make a footpring in the upper with use.
Just lube the upper and BCG well(wet) with a high quality gun oil like Weapon Shield CLP and run it.Once everything has settled in the wear will stop to a certain extent.
As a matter of fact,pictures of wear like this would probably be a good thing to add to the PM and inspection thread/sticky.
Here is a link to a recent thread on the subject with pics.
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Originally Posted by Todd.K
Because AR type 308/7.62 rifles are not all the same like 223/5.56 rifles, you should not call it an AR-10 unless it is Armalite pattern.