a .312 cast or jkt bullet may expand case neck so much that ctg is a jam fit in the chamber(not good). .311 is max for my .30 tok in cz52 and same for my buddy's broomhandle in .30 mauser. A die set expander for .308 causes serious problems for .310-.311 bullets. Flaring req'd, gentle seating with a bullet matching seating punch, rotate ctg as you seat in stages or bullet may go VERY crooked and bulge case neck. My Lee .30 tok expander die was hopeless. I use a 32 acp or 32 s&w rcbs expander or lyman multiexpand powder thru die. Be patient til you have a method.