You could scrounge up some Browning Li'l Skeeter 16-20 ga chamber inserts. I have 10 and they work well. The down side is one needs a dowel or something like it to punch out the fired rounds. I use a bullet starter from my black powder rifle as the ball on the end is easier to grasp and is not as hard on the hand.
It goes easier if one can use the long discontinued Winchester compression formed AA style hulls. The black Remington hulls and the current ones by Winchester and Fiocchi aren't too bad either. The Federal hulls are the hardest to push out but it isn't too bad. I have the number I do as I'll use them for sporting clays and I can get through a station without needing to mess with reusing an insert. Reloading them all after shooting or at the next station while waiting to shoot is fairly quick. I can keep up without hurrying with 4 others in the squad.
