Just got a Tactical Solutions AR upper and ran about 300 Federal Walmart rounds thru it today with zero malfunctions. Sure beats .40 a pop of .223. Also had some fun with the Ruger Mark II. Just plinking around is a good way to spend the afternoon. Overall I'm really pleased with the new upper, I expected at least a few malfunctions with breaking it in, the bolt is nicely polished stainless.