WHAT DOES CUSTOM FIREARMS MEAN?

I’m in a small town 40min South of Denver, CO. I joined primarily to find out additional information on my father’s 1959 Design 70 .300 H&H Magnum. I don’t hunt, so I’ve only taken it target shooting so far.My very first 1892 is greatly like yours besides that it’s a rifle and has not been refinished. Bore turned out to get far too tough