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The upper receiver and its post-anodizing feed ramps wouldn't worry me. Even Colt did the same on the 6520's.
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Yeh, I have a 6520 and it looks like Colt outsourced the dremelling to the Century drunk monkeys.
I'm replacing that upper with a C7 and reworking the carbine into a 723 clone (retro lemonade :) )
The problem with dremelled feed ramps, even if done at the correct angles (which my 6520 from the factory obviously was not), is that type III hardcoat anodizing significantly hardens the surface compared to the raw aluminum, which is exposed when they dremel through the anodizing and expose white metal. So, if the bullet tips actually impact the part of the ramp that is receiver vs barrel extension, that could develop a problem over time.
Of course, in 2008 when I ordered it (the first Obama panic being in full swing, it took about 6 months to deliver) I didn't understand all this stuff as well as now, so on the online order form I selected "M4 feed ramps", which apparently translated into the dremel thing. To their credit, at least the portions of the ramps in the barrel extension and the portions in the upper actually line up (it looks like they did it with the barrel & upper already mated). That's better than Colt. When I sent the 6520 back, they "fixed" it by dremelling some more to widen the ramps in the upper so that they now overlap the ramps in the barrel extension. I bought the 6520 from CDNN for a nice price, but I guess you get what you pay for.
Nothing against either of these companies in general. I think Colt is the gold standard (when they don't cut corners - and usually they don't - they gave me an RMA in a heartbeat and I was actually surprised they didn't give me a new done-right upper receiver instead of doubling down on the dremel). I think CMMG is a solid mid-range AR vendor, and not their fault that my champagne tastes outgrew their Napa Valley offerings. I probably should have bought a Colt or BCM A2 to start with.