There used to be some reliability issues in the past, but a bunch of us just completed a group buy on MCC ammo and it works as SS109 should, wonderfully. Also included in the group buy was some 308 AP ammo, and 308 match ammo.
I also feel comfortable in speaking for the entire AR15.com community in saying that MCC has the absolute worst customer service and communication skills conceivable. I mean, even Coal Creek Armory would say these guys were horrible at fulfilling their contract. QuietShoez himself would gawk at their ethics. MCC is in my opinion a royal pain in the ass and although I think their ammo is fine, their owner and operator is a dub.
If you find some MCC ammo at the local store, fine. It'll work as it should, the quality of the ammo itself is good. But lord help ya if you want to talk to the yahoo that runs the joint.
That is all.