ED;
Everything is relative. The question is relative to what. A heat of 200F would be perfectly safe to a heat treated piece of steel, but Highly Detrimental to a Snowman. Temperatures relative to when a heat treated part will be affected are very well defined indeed. You've beat around the bush with "Relative" terms about long enough. If you have no idea how hot you are heating a part then it would be highly advisable to stop heating them. If you know how hot, then come forth & say so.
These old guns which originally had case hardened frames were all made of a low carbon steel. The core beyond the point the carbon was "Cooked" into do not harden in the quench but remain soft. Only the case hardens. It matters little whether the original piece of steel was a 1008, 1015, 1018, 1025 etc the process is virtually identical. When one gets into through hardening alloy steels then it becomes much more criticle to know what you are working with. These early case hardened frames are built of a pliain low carbon steel. Even some steels having some alloys but retaining the low carbon content can be case hardened by the same process without any special attention. This is all a matter of metallurgy, not VooDoo.
