MohawkSlim
Expert
I've seen two ARs in the past two weeks with out of spec rings. One had a single ring that was bent upwards at the tip. The other was obviously too large and scraped the carrier each time it moved.The bolt would move into the carrier with some resistance. It would pass the "stand it on end and the bolt shouldn't move into the carrier". However we didn't take the bolt apart and inspect the rings. Interesting idea.
If you've changed your BCG and it starts running fine... you've narrowed down your problem. It's in that old BCG somewhere. The new one worked fine with the "bad" charging handle, right? It's not that then. I'd put my money on out of spec gas rings in the "bad" BCG.
And spending money doesn't necessarily mean you won't have issues. ARs are finicky. Spending extra money might not mean you're going to get one that works for you. I bought a really nice Colt Match Target Rifle and it had issue after issue. I swapped the bolt with a standard GI bolt from the armory, and it ran just fine. These cheap "entry level" ARs are more than adequate. You may have to piece them together till you find what yours likes, but who cares what the roll mark says as long as it works.