The obscure facts of how some parts of double barrel shotguns were made and from where the materials came from to make them was commented upon by Jack Rowe during a conversation I had with him in 1998. We were discussing how that some double barrel shotgun trigger guards would eventually turn a plum color, no matter how you blacked them. Jack explained the reason of this. He said that the lads in the gun trade such as him would sweep the floors of the gun making shops gathering the iron and steel filing along with the dirt and grime and collect all this iron/steel/dirt mess into a bucket or barrel. Later the junk man would come by and purchase the barrel or iron/steel/dirt filings and the money the shop received was beer money for the shop workers. The "bucket of grime" was used as the basis for melting and forging then producing strips/bars of "steel" from which trigger guards and other parts were made. Not all guns trigger guards were made of this junk steel but the less expensive ones were.
Jack Rowe may be a London trained gunmaker, but his explanation of why certain gun parts turn a plum color when blued or blacked seems implausible at best, and based upon pure conjecture. It is a quaint story, but likely has zero basis in fact. I'd hate for this sort of probable misinformation to become accepted as fact, and then endlessly repeated on the internet.
By the 1870's-1880's, steelmaking in England was pretty advanced, and among the best in the world. They were producing over half of the world's steel production, and the days of crude and inefficient processes were over. They knew how to make large quantities of quality steel in such an efficient manner that the price of new manufactured steel had dropped to around 4 Pounds per ton, from over 50 Pounds per ton prior to the invention of the Bessemer Converter in 1856. By 1868 a Metallurgist named Robert Muchet had developed the processes to effectively purify steel, and to then add certain elements to get the desired alloys of steel. They understood the chemistry and were well past the time when it was a seat of the pants affair that produced a sometimes unpredictable result.
Steel soon became one of the most recycled materials on Earth, and it still is today. All manner of steel may be collected as scrap. It is then segregated to the best practical extent, and then added to new steel produced from iron ores of varying quality and chemistry. But there will almost always be a certain amount of contaminants in the scrap, and most of those impurities will be removed during the steelmaking process, or end up floating to the top, so it ends up in the slag ladle as a waste byproduct. Consider the baled and cubed scrap automobiles we see on their way to a steel mill. They are mostly steel of different alloys, but they also contain plastic trim, vinyl, broken windshield glass, aluminum, and perhaps worst of all, copper wiring. Copper contamination is one of the worst and most difficult to remove contaminants, and is best physically removed to the greatest extent possible, and otherwise diluted by the addition of non-copper bearing scrap.
The best explanation I have heard for steel turning a plum color during or after the bluing process is that the steel may have a high nickel content. Gunsmiths have noticed that certain guns containing nickel alloy steel, such as 1930's Winchester Model 12's are prone to this malady. Post 1964 Winchester Model 94's used a different alloy for their receivers, and hot bluing it resulted in a red color. The solution was to first iron plate the frames. Polish that iron plating off during refinishing and you've got problems. I have a Mauser Model 66S rifle in nearly unfired condition that has a plum colored receiver. Everything else is a nice high gloss blue-black. I'd say there is zero chance that it was made from dirt, garbage, filings, and machine chips swept up in some factory. One problem with steel is that all of it is is an alloy of some sort. You can't just select a piece of steel by looks alone, because the chemistry and qualities may be very different due to the elements alloyed into it. Some steel may be hardened for various cutting tools or springs, while another piece that looks identical may not take hardening at all. Some steel welds better than other types. Some wears better and some is more or less corrosion resistant. There are specialty steels that are best for laminated electric motor armatures and transformer cores, because they produce less Eddy currents under the influence of magnetic fields. There are some very specialized steels that contain no radioactivity, since all virtually steel produced after the atmospheric testing of atomic bombs contains traces of radioactive contamination. It all eventually ends up as scrap, and it is all called steel.
It seems far more likely that the trigger guards and other gun parts that turn a plum color when blued or blacked is simply due to use of an unsuitable alloy. The gunmaker needed steel and bought steel... but it wasn't the best steel for gun parts that would be blued or blacked. It would take metallurgical testing by a good Met Lab to know why certain trigger guards, etc., may turn a plum color.
