Spikes flat top upper - Spikes Tactical M4 Flat Top Upper

I bought this upper for a lightweight 300 Ham'r build, and finally got it all together. On the positive side, dimensionally its very good to excellent, and the external finish looks great. In addition, I square the front of uppers before mounting the barrel, and this one came square. It built up nicely. In the down side, the inside of the upper was barely if at all all finished, looked like overspray. I'm concerned about wear on where the bolt rests. I have not fired the upper yet, we'll see how it does.