Once again, I posted this in the General Firearm area, but I want to keep the thread alive here as well.
I called bushmaster and talked to a fellow named Jim. Cool guy and answered all of my question and even explained to me from beginning to end the entire cycle of the AR.
After telling him my issue, he agree'd 100% there is a gas leak somewhere.
I asked him, "what about the first 30 rounds working great".
He thinks when I clean it , the oil finds its way into the carrier key bolts, it is enough to
keep a "seal", until I shoot it couple times and the oil is all dried up by then, and at that point, there's no longer a seal.
So I say, "so you think this issue happening right after I get it back from you guys (bushmaster) and this issue is a coincident?"
He says, "yes".
He says to look at the screws that hold the carrier key to the bolt carrier. He thinks one of them is either cracked or needs to be tighten.
I have a hard time believing that the two are not connected, but nonetheless, he was nothing but nice, offered nothing but help, so I'll try what he thinks it is and I'll go from there.
I'll update this post tonight to tell you if Jim was right or not, for those that actually care about my issue.