I have to agree with Rich Pierce, I don't do anything to reduce the value of an original, and prefer reproductions for shooting.
If you do wish to go ahead, then there are several thing to remember... Safety being the most important ! You will be dealing with extreme heat, and quenching liquids that are flamable themselves. I know this may not be your first rodeo, but we can never be too carefull...
Enough of that. It is best to try and get a rockwell hardness test of the part before altering, so that you are aware of how hard or soft the original part may be, you can also compare the hardness of a similar part, to get an idea of what hardness to acieve when finished. Your first process is adding a build up of metal or stock that is needed. Step two would be to normalize the metal, a cherry red held for 7 minutes, this process will stress relieve the welded area as well. Conduct your finishing process by filing and polishing at this point, take it down to the almost phase and leave the final polish and stock removal for after hardening. Did I mention that you need to allow the part to cool to room temperature after each process?
Heat your part to yellow, or straw color, this will allow all of the constituents to combine. Hold at this color for 5 minutes, being carefull not to melt or scorch certain areas. Quench in a semi heavy medium, at room temperature, 5W30 oil seems to work best, unless you are able to get your hands on a professional quenching medium. Use adequate ventilation while doing this as you will produce some flame and copious amounts of smoke, outside is best to keep the wife from yelling at you! Move the part around in the medium, so as to eliminate any gas pockets that will affect the structure of the metal. At this point your piece is at it's hardest point. It will have developed crystalline structure known as Austenite, so try not to bang or drop it. If left in this condition, it could fail, so the next process is annealing. Clean any scale that has built up on the part at this time with a wire brush.
To anneal we need to relax the metal, and give it a more flexible core. You need to reheat the part once again to a blue, or brown color and attempt to hold it there for 1-2 minutes. You can bake the part in your oven at 475 degrees and hold it for 5 minutes if you like. However, you will need to quench the part in the medium once again until cool enough to handle. A final cleaning and polish can be done at this point. The part is ready to use...
That is the Blacksmith's version of heat treatment, but it is best to know the exact temperature that the part needs to reach for each step, utilizing heat treating manuals for specific metals. This process is not fool proof by any means, and it may be by trial and error on one's first attempt. It also has alot to do with the type and quality of the metal, as to the results that you achieve, however the way described is the simplest and one most of us can afford. I was formaly trained as an aircraft welder and machinist, and have seen parts that were properly heat treated fail under normal conditions, so inspect any repaired parts on a regular basis to ensure a long life for the gun. Also keep in mind that if two parts come in contact, they should be of similar hardness to reduce excessive wear on one or the other. In example: The trigger and sear arm, tumbler and sear ect. Modern steels are of a much higher grade today so do not mix and match. Hence the reason most of us will only use modern reproductions.
Hope this helps.
Daniel
