The tapered sheet iron tip seems to be the most common. These were on the end of the rod that goes into the ramrod hole... not on the end you see at the muzzle when the rod is stored. That's why they were tapered... to match the tapering of the rod. Here are the measurements from the "ETC" Hawken rifle owned by the MT Historical Society...
Ramrod Overall Length: 38 13/16"
Diameter at Middle Area of Ramrod: 0.368"
Diameter at Large End of Tapered Iron Tip: 0.288"
Diameter at Small End of Tapered Iron Tip: 0.230"
Length of Tapered Iron Tip: 2.150"
The tapered iron tip is made from flat sheet iron, rolled to a tapered cylinder, and with the seam brazed with brass. It is threaded, but I didn't have anything to measure the threads.
This is consistent with others I've experienced.
Regarding the "ETC" Hawken... The rifle is .50 caliber. The other (muzzle) end of the rod has a brass ferule. It is made from seamless brass tubing, flared at the end to form a trumpet (bell shape), and is open on the end. In other words, wood is exposed at the end. It is held in place with a wood wedge driven into a slot cut into the end of the rod. The muzzle end brass ferule measures 0.442" in diameter (at the big end) and is 0.661" long.
A ferule was added to the muzzle end of the rod to prevent splitting. Sometimes it would match the metal type of the muzzle cap, but sometimes it didn't. The Jaeger book shows some closed off with a disc of matching metal brazed or soldered into the end, but a lot of them were left with the wood exposed. Cupping the muzzle end was common. I don't believe these were ever threaded... but never say never.
A plain wooded end would be more common on most rods. I think the fancy tips were used mostly on fancy guns.
I'd bet money that if an original rifle has a ramrod with a solid brass, iron, of silver tip... at the muzzle end... that's threaded... it's a modern replacement.