I'm with Joe on this. First you properly measure the chamber and then you buy or reload suitable ammo for the gun. Opening the chambers on an antique gun to shoot current over the counter ammo isn't likely to be good for the firearm. Once you know what the gun needs suitable ammo is already available for it in most cases. RST and others make low pressure, 2 1/2" shells which actually turn out to perform better than most of the shells available over the counter anyway. Or if you are already a reloader the load information is available.
