I thought that the Ranger was only chambered in .30-30...Sure it is not a Trapper or other variant?
Modern rifles chambered for .357 Magnum will chamber and fire safely all current Factory .38 Special and .357 Magnum cartridges...
The ammo manufacturers keep them slightly below SAAMI max's because they do not know what the condition of the gun or type of gun (pistol/rifle) they will be used in...
I have a Marlin lever in .44 mag that I load max for the rifle, but when the same cartridges are fired in my pistol, the rounds are nearly a grain of powder under 'max'...