My bushy upper is experience weird wear on the inside of the upper.

The wear is in between the chamber locking lugs and the notch cut into the receiver for the CAM PIN to rotate in.

___    ___CCC  
  N__N

N= notch, CCC = chamber.

The wear is on the track in between the cam pin notch and the chamber. After every range session I have a *small* bit of aluminum shavings. The area is worn silver, but is quite smooth. The carrier is shaving away this slice on its return stroke no doubt.

Is this a common thing to ARs? My ar has less than 1500 rounds through it.

Thanks!

I have the same wear if you turn your upper upside down and look through the ejection port its right before the notch and curves inward.I have put more than 15,000 rounds through my upper and no problems its the same with my other 2 bushmasters.I think its just due to the carrier cam pin breaking in the upper. I dont get shavings but then again my upper has seen alot of rounds I dont think its something to worry about maybe some one else will chime in to let us know if their upper is the same way on the inside as it gets used .

If this is the part that mates with the top corners of the carrier next to the bolt cam pin its normal break in and it wont be fully broken untill the parts have worn together.  You probably can get your carrier and bolt to not close and can use the forward assist to close it if you slowly chamber and lower the carrier by the charging handle.  One its broken in you cant get the carrier to hang up even if you try.

Suggest you take this over to the "Troubleshooting" forum, as there are lots of savvy folks there. Also if you can post a pic, that would help.

I've seen very few AR's do anything more than cause some finish wear inside the upper, and if you're still seeing metal being removed after 1500 rounds I'd say it's something to be checked out. If you bought the gun/upper new, you might want to give Bushmaster a call.