once that area is black again, you've broken the rifle in.
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once that area is black again, you've broken the rifle in.
Every upper I own has this type of wear. It is normal.
100% normal.
Thanks for all the replies. I had just not seen this level of wear so quickly in my other carbines/rifles, and just wanted to be sure that I was not missing something with my first SBR/can.
I have just completed a MK18 build and while not worrying about the wear I do think that the removal of the anodizing occured faster than with my other 14.5" or 16" guns. FWIW I am using an H2 buffer and not shooting suppressed ... yet.
Totally normal about some "wear"...if it really bugs you..get a POF roll pin setup...but honestly...you wont need it
You're fine. My 5.45 AR has more and it's rock solid.
I think you'll find that cam pin lash is the primary cause of the wear. If someone else can verify, I believe the TDP spec for the cam pin diameter and the hole in the bolt are nearly the same. To speed production and reduce returns, a manufacturer may make the hole to big or the pin to small.
When the pin is too small or the hole to large, the unlocking force isn't lateral to rotation of the bolt and the pin rocks in the bolt hole. This leads to impact between surfaces (cam pin and upper receiver) and varying degrees of wear on the corners of the cam pin relief cut in the upper receiver.