Metal
They all chambered fine , checked in Lyman case gage , MAXXTECH cases are the thickest I ever came across , most went all the way in the case gage a few stuck out slightly but passed the plunk test . Passed them through the FCD felt a slight resistance when first going into the die and then seated fully in the gage , case thickness is the issue , if I didn't check my reloads they would have fired without a problem but I do , that's just me . I do like the die .
Chris