New models of guns always have better technology. My old M1-90 never did that .I'll have to upgrade !
Flames out of the end of the barrel are far more common and the donut of smoke too. Ever see the the monster donut coming from a huge battleship gun ?
It's all from powder still unburned after the bullet leaves the barrel. I assume that the shotgun still had unburned powder in the shell and when the extraction started the air coming into the case burned up the powder.