I've seen this on both S&W factory guns, new and old, as well as refinished guns. Most of the factory purple I've seen have been on older S-prefix model 28's and 1980's production model 17's for some reason...maybe just coincidence. It's almost always the cylinder, barrel, or both and almost never the frame. Maybe that's just another odd coincidence.

I read the story on post 1964 Winchester's not taking to re-bluing well when some kind of ferous coating under the factory bluing was polished of the steel, but I don't *think* S&W ever used such a process.

As always, I appreciate your insight!

I don't know about original finishes but on re-blues with hot salts it seems to be caused by the alloy. I believe it is the nickel content but it could be something else. Leaving the part in the tank longer seems to cure it. WWII Springfields are notorious for coming out purple. I have also noticed that the color will sometimes will not come out for months or years. It is always the high strength parts.

My understanding is it is a combination of the steel used and the temperature of the salt bath. I suspect the steel used in the barrel and cylinder are similar and different from the frame to account for the color difference, but it may also be the frame is blued in a different tank or solution.

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Alan
SWCA LM 2023, SWHF 220

Some of it is caused by the heat treatment. Ht treating causes the iron carbon matrix to change its configuration. You can actually see it in the steel if deferentially hardened. Look at this blade.

http://www.camererknives.com/images/r1.jpg

The most common reason for purple or reddish colors of bluing is the bluing process is out of control or the chemicals were getting depleted.
Out of control temps seem to be the most common reason.

Yes, heat treating and type of steels can make for odd colors, but after 150 years or so gun makers know all about that so they don't use those steels or heat treating processes on frames or major parts.

The most common place you see these colors is on re-blued guns done by a local gunsmith who doesn't do it very often.
They often allow the process to get out of control, the mix of the chemicals to change, or the chemicals to get "worn out".

Some gun makers, even very good ones sometimes let the chemicals get a little too used up before changing or may even allow the temp to get out of control slightly.
In the case of a big maker the usual odd color is a purple that may not be evident until some time has passed and the bluing has had time to oxidize.
What looks like a good blue in the factory, after a few months or years may take on a purple cast.
Often the purple or even red color isn't apparent until the gun is taken out in the sun.

Among the cases where it was the metals, were the contractor-made purple cylinder releases on some 80's blued Colt Pythons.
For a time Ruger had a problem with purple revolvers due to the new casting metals they used.
These are now collectible guns.

The post-1964 Winchester Model 1894 was a major mistake. Winchester went to cast receivers using a metal that refused to color properly and came out a weird red color.
In order to solve this until they could figure out a permanent fix, Winchester iron plated the receivers, then blued the iron plating.

The "fun" started when attempts were made by gun refinishers to re-blue them.
Not knowing about the iron plating they polished the thin plated layer off, then were shocked when the receivers came out an ugly red color.
Winchester heard about that one, which helped ruin the company.

As stated above many things can cause purple guns. Most of the time it is the type of metal being blued. I have a H&R 22 revolver that has a frame that refuses to darken to blue. Its barrel and cylinder are really dark but the frame is purple. You really have to know the metals in the gun to be blued, frame, cylinder, barrel and any small parts. Many of the new guns cannot be hot blued due to the metal they are made from. The only option is cold bluing or rust bluing if it will take.

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Tom
NRA Pistol Inst

Some of the above posters offer a few plausible explanations and while I have no words of wisdom to add on this subject I will state that it is not uncommon and I have seen it on occasion.

The bluing process, obviously, has been changed due to environmental concerns. That in itself changes the color somewhat. You will get a more pronounced effect if you use any cleaners with AMMONIA as an ingredient, including the old Hoppes #9. There is a new formula to be used with newer guns.
Smith and Wesson SHOULD be more forthcoming about this. They've made statements and it's not a secret, but the only people that find out about it have purple guns.

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"He was kinda funny lookin'"

I have a custom built 98 Mauser. Had it rebarreled to 243. Since
my uncle gave me the rifle, a WW2 bring home I had all the
German markings left in the reciever. I had a Douglas premium
barrel put on it. I think it was a new Chrome Moly Steel that they
had just came out with at the time. The action came out the most
beautiful blue you could ask for, as well as all the other parts. The
barrel came out a very rich purple. The Smith was going to blue
it again, but I kinda liked it and told him not to bother. This guy
was no bubba, he was well know for his blue jobs. I have always
believed this was the alloy in the barrel. That was 1964, gun
looks the same as day it was put together. The tone of the walnut
stock has changed over the years, making the gun look like it
was planned to be that color.

Nothing to add about the causes (the subject has been covered), but a comment about heat treating and bluing...

I have a mid-1970s Anschutz .22 where the action bluing is not a consistent hue from front to rear. The heat treat was not uniform by design; part of the action was spec'd for different heat treatment, and this was valued by the manufacturer more than aesthetics. Many years later, I remember reading that they were changing the heat treatment of the actions to be uniform -- not for function but for uniformity of the bluing (aesthetics).

How they look seems to be more important for most of the gun buying folks than how they shoot. Same with knives how then cut takes second place to how they look.