vharis, I'm going to assume you cleaned & lubed yur extractor when you swapped in the .243 extractor. .............. I've got a Mod. 12 sing. shot in 223. I use Rem.( .377" head dia. ) & LC '09 Brass (.373" head dia.) My bolt face I.D. is .381". Both cases feed flawlessly even w/ the variance in head dia. The dimension variance is typical for Mil spec vs. commercial brass. Hope this will shed some light on the problem. I suspect your bolt face is a bit large but I could be wrong....... You can get a new bolt face from Savage or Midway. If you get a new bolt face check the ejector hole interior for galling........... Galling will effect plunger spring performance & lead to yet another round ( pardon the pun) of difficulties. Keep us posted! Dale