You can make a simple tool to get an almost perfectly round tip on your ram rod.
Take a price of wood, a 1x2 or something similar, and drill two holes of the size you are working with in it, one all the way through and one to the depth of the tip you are instaling. Next, saw down into the hole that only went part way through cuttin it in half, then remone one of the halfs leaving a half round hole with a bottom in it.
Start reducing the diameter of the ram rod in any way you chose start. As you go checking the diameter with the wooden tool. First rub the inside of the half hole with a pencil, then rotate your reduced ram rod against the side of the half hole. The pencil lead in the hole will rub off on the high parts you've left. Carefully remove the high marks and repeat the check until you get pencil lead almost all the way around the ram rod tip. Check the size of the reduced tip using the hole that went all the way through the wood. You'll have an almost perfectly round cut on the end of your ramrod of the correct size. You van do It all with a sharp knife with no need to turn in any way.
Another thing, I prefer cylindrical brass tips over flared tips. That way you can slide the brass tip into the ram rod hole in the stock. Then when you load you can simply pull the rod out, move it over about an inch and start ramming.
With a flared brass tip you have to pull the rod out, flip it end for end and then ram the ball. It introduces an additional move to the loading process, and sereves as a flag to game. It also slowes the reloading process, which cold be an issue if you ever use your muzzleloader in combat.