What he is talking about is exactly what happened to me. I took it home didn't take it completely apart, just opened the receiver the gas piston and trigger group, should of stripped everything down but I didn't, and I realized I didn't clean it off enough. It was Hella hard to get that gas piston off as he mentioned, but I eventually got it loose. I used Engine Degreaser from a motor parts store. I was anxious to take it out and so it didn't get cleaned properly. The first rounds I put through it, it failed to eject about every 4 shells, got better as time went by. As I kept shooting it, the intense heat melted off a lot of cosmo, it was all over the gun and the barrel! I didn't realize this much was on it. Took it back, cleaned it once more and now it shoots great. But it is definately about getting that Cosmo off. my 2 cents.
-mark