Since most original ramrods that are available for study seem to be tapered with a swelled end that is near bore size, that is how I make mine. I use a 6" X 48" belt sander with an 80 grit belt on it. I usually start with a 7/16 rod for 50 cal & up. I roll the rod while I twist it with my fingers across the running belt. The rod is lengthwise to the belt not across. It only takes a few minutes to taper the bottom end of the rod down to the diameter to take a 5/16 end tapped for a 10/32 thread. If you get the rod a little elliptical, it can be rounded up by pulling the rod through a piece of angle iron that you have drilled a series of holes from 1/2' down to 5/16. The iron is clenched in your vice , and if you pull your rod on a slight angle it will peal wood off quite quickly and round thing up. It probably takes about 10 minutes to taper and fit a rod...
Ron