mauser
In a standard M98 type bolt, the cartridge head recess opening typically measures about .004 to .005 larger than the .473 diameter of a 7mm or7.9mm military cartridge rim. The 204 Ruger is based on the necking down of the 222 Rem. mag., with a case head diameter of.378, that said i would look for an action with a.378 bolt head (222-222 mag.-223 Rem.). Hope this answers your question!