What is the distinction between these?
~~Range rod
~~Field rod
~~Ram rod
Ramrod - the rod that is made for the muzzleloading gun or rifle, which is used to load the piece, whether original or a reproduction of an original gun/rifle or style of gun or rifle, and it is fitted and stored on the rifle/gun.
"Rammer"-- slang term for ramrod, and often heard among living history participants who recreate a soldier... included as a response to the OP as one sometimes hears this term..., so included to avoid confusion in the future....
Range Rod - usually a rod made of highly durable,
modern-ish materials such as Delrin, steel, nylon,fiberglass, or brass (hence "modernish" as brass or steel are very old metals). The rod is used instead of a more fragile wooden ramrod when the shooter is at the range (hence the name) for loading and other tasks. Most commonly they are also longer than the proper ramrod for the gun/rifle, and are easier to grip and use.
Field Rod - similar to a range rod these are often made of a material other than wood and thus are more durable, and are used when hunting "in the field" so the shooters does not damage or break the proper ramrod that is normally displayed on the gun/rifle. These tend to be fitted and carried as a replacement for the traditional wooden ramrod when in the field. The smaller the caliber of the rifle, for example, the more fragile the ramrod, and thus one often sees those using .36 or .32 rifles for hunting, having a field rod made of material more durable than wood.
LD