ok then
a smoke ring is the interaction of the myoglobin in the meat and nitrogen oxide
want good smoke ring, do not warm the meat to room temp, the longer it takes to warm up in the smoker the better the ring
and................. use some bark for smoking, it seems that bark has more nitrogen oxide than regular wood.
I am a bit lucky in that because I harvest my own wood, well lets say I buy it in stick form, not in chunk or chips, I live in the desert and get mesquite every fall and let it cure. I go to the apple farms in the winter up in the local mountains and buy the wood they prune off, I do not want the thick stuff, I get the stuff I can get goof chunks from easily, it also has more bark to the pound than logs.
So, meat not warmed to room temp, bark. makes the best smoke rings
I am not saying you have to do it that way, just that is the best way to get a good ring. What you are doing is a slow cook with nitrogen rich fuel. giving the agents causing the ring optimum time to react