A friend has some plastic bullets and cases made by speer that are fired/propelled by a primer. In this case we were using .44 in a revolver. They really worked well except that in his SW revolver some of the cases hung up and the cylinder had to be helped to rotate.
I liked the idea of being able to shoot at home, in the garage, over and over for just a few pennies. Especially when it is cold out.
I looked on line and saw some rubber bullets called X-Ring that are put in brass casings with a primer and used the same way as the Speer.
My first instinct is that the brass cases, designed for the caliber, won't hang up like the plastic ones were doing, but I have no way to know how well the rubber projectiles work compared to the plastic.