That is one of the OEM Breech plugs. Either the 7/8" or the 5/8", depending on the year of the Huntsman. You cannot tell which one by looking at that end, until you remove it at least part way. 2002-2004 used the 7/8", 2005-2008 use the 5/8". They both use the orange primer carriers for 209 primers. 
 Your rifle is a 2003, and will have the 7/8" breech plug. 

  OEM Primer Carriers, fired on left, new on right. JUNK, IMO. 
  OEM Breech Plug Tool on left, Customized Tool on right. 



  Did I mention, I HATE THE NEW PHOTOBUCKET???  
OEM Breech Plug on left, Hubbard 209 Breech Plug on right. 
  Top wrench for OEM and Hubbard Plug, bottom wrench for Hubbard 209 nipple. 

  This is a 25 ACP Conversion. 
  L-R; OEM Breech Plug, OEM Breech Plug with my Easy As Pie #11 Conversion, OEM Breech Plug with OEM Primer Carrier and 209 Primer, .25 ACP Breech Plug, Hubbard 209 Breech Plug. 

  Hubbard Breech Plug with 209 primer nipple removed and #11 Knight nipple in place. 



  Aftermarket 209 breech plug, 7/8" top, 5/8" bottom. 

  My Easy As Pie #11 Conversion. 
  My Custom 209 Breech plugs with removable vent liners. 7/8" top, 5/8" bottom. 







  With some Lehigh Vent Liners. 
  It's not a sickness, really! I cleaned out the bottom of my range box one day, it's much lighter now. 
  Confused yet? Just wanted you to be aware there are alternatives, much better alternatives.