Let me add, because you mentioned the BP screwing in. A new plug still screws all the way in, but leaves a small 1/8" gap. It's that gap that's the fitting. Maybe even less than 1/8". You're not messing with the threads. Just fitting the ring at the bottom of the BP. It needs to fit snug. It keeps the crud from going into the threads. That's why it always unscrews by hand.