Yes thats the "special tool" plug. You can ask if anyone has one they can spare on dougs or get one from Savage. I would recommend you replace it with a hex head plug.

Hard to tell but it also looks like the plug is nearly filled with carbon too.

Luke at Arrowhead sells the OEM plug or a OEM plug with a tungsten carbide bushing. The bushing last a really really long time compared to vent liners.
http://www.smokelessmz.com/upgrades.html

Hankins rifle also sells the plugs and his are SS.
http://www.hankinscustomrifles.com/...pplies/muzzleloader-building-components/