Upper End (or ball seating end) of Thompson Center Hawken or Renegade ramrod. Cupped for pushing patched ball down the bore. 1-3/4" long, about .430 diameter at largest point. Brass for Hawken, Steel for Renegade.
Brass jag for 5/16" utility "Super Rod" listed elsewhere on this site. Available in .32, .36, .40 calibers.