If it is a Sweet Sixteen its probably fine to shoot with modern loads, but if it a sixteen gauge A-5 it may be an older gun. I have my Grandfather's A-5 16 but it is a '30s gun and I don't shoot it anymore.
There are two ways to set the spring and friction rings. Illustrations are easy to find. I'd set for the heavy load and shoot the lightest load it will eject. If the gun has original 2 3/4 chambers it probably a later model...Geo
P.S.: I'd bet RST's will fail to eject. Number 7 1/2 or smaller steel shot would probably not be a problem.
