gunsmithing, ar-15I built an M4 style AR15 last year for fun and ran about 200 rounds through it. When I went to clean it, I noticed a small burr below the left feed ramp (rifle style feed ramps) where it looks like maybe a case neck caught the edge of the upper receiver and chipped it. Not deep, just enough to get through the anodizing. I haven’t had a chance to bring it to the range since, but I don’t think it will affect functionality. Is there any problem buffing that tiny lip smooth and should I bother spot anodizing it? Has anyone else with a rifle ramped AR noticed wear on the receiver below the ramps?
As long as you don’t directly affect the feed ramps themselves (which you shouldn’t since there are no extensions into the upper on rifle-style ramps) you should be fine polishing the raised portion flat. Re-anodizing is more trouble than it’s worth; I’d cover it up with something Duracoat or CeraKote, or just leave it be if you’re in a dry climate where rust isn’t an issue (unless you remove the anodizing on a large portion of the upper in your attempts to fix it).
I’ve never seen this on my guns either personally owned or issued. Then again, it’s never really been something I’ve looked for (meaning it never caused me any malfunctions if it’s happened to me) and I’ve always had m4-style feed ramps so my ramp extensions in the upper are likely where this would have happened to you.
Polishing the aluminum won’t hurt at all (other than the finish). Since aluminum doesn’t rust (it does oxidize, but that happens in seconds and isn’t something to worry about) you don’t need to worry about refinishing except for cosmetic purposes. Anodizing would require complete disassembly - there isn’t a common spot anodizing method - it’s normally an all-or-nothing proposition.
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