The only issue I've ever had with "dirt" in an AR was caused by steel-cased ammunition leaving lacquer in the chamber (won't ever shoot Wolf in an AR again!), and that wasn't so much of a "dirt" problem as it was a "casing failed to extract and the extractor ripped a chunk out of the case" problem. From time to time, I will take apart the BCG and clean the carbon buildup off the bolt and from the inside of the bolt carrier, and I'll scrub the locking lugs with a wire brush, but that's more of an "I was told buildup here can cause problems" thing than an "It has caused problems" thing.glbedd53 wrote:I like my ARs, but I love my AK. AK has another advantage over an AR. It don't care if it's clean or dirty, wet or dry.
Unless you're carrying and using the rifle on a daily basis, I expect it'd be pretty difficult to gunk up an AR to the point of failure with simple carbon fouling. I know I've never managed it.