the way i understand it...the metal used in these mauser do not have high enough carbon content to be heat treated...carbon must be added to the surfaces ...usally with gas thats high in carbon while its in a heatreat oven.,.or packet in a high carbon powder while its in a oven...then after all this it must be quenchted in water cooled then reheated to a lower temp to lower the hardness ..
not your average heat treat job!!!! search some of the other post you will find some addresses of heat treat people