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Rugers turning purple

6K views 9 replies 7 participants last post by  Lone Star 
#1 ·
This question has probably been asked before but I'm a newbe here so here goes. The blueing on the receiver my 20 year old M77 RSI 30-06 has turned purple. I have noticed the same thing on the loading gate of my 1960 vintage Super Blackhawk. Anyone have any idea why this nappens?

Thanks in advance for any info offered.
 
#2 ·
jisii, The collector word is "plum". It happens because of the alloy Ruger uses and sometimes doesn't show up for several years after the gun was blued. It doesn't hurt a thing ... just a cosmetic issue that really appeals to collectors.
 
#7 ·
In times past, and on other metal objects (Vietnam era combat knives) plumb colored bluing was due to the bluing solution not being hot enough. The reason it was not hot enough was a misconception that too high a heat would anneal the hardened blades. Could this be the issue here?
 
#9 ·
support_six, Quite the opposite .... bluing salts boil at 292 deg F with the proper ratio of water-to-salt, (10 lbs salts for 1 gallon of pure water) which is the ideal temperature and mixture for bluing guns. Water continuously boils off and makes the salt solution more concentrated, which in turn requires a higher temperature to keep the salts boiling. If water is not continuously added to compensate for boil off, gun metal will start turning plum and keep getting more red as water boils off. So the "Plum" color in steel alloys comes from the bluing salts being too hot (too concentrated) ... not too cold and the color will show up as soon as you pull the metal out of the bluing tank.

Annealing is a process where a metal is heated then cooled quickly. Typically, water or oil is used to quench hot metal. Metals have different properties ... brass or copper will get soft when annealed, however all ferrous metals (iron, steel, and knife grade stainless steel) will get harder when annealed. It takes about 300 deg F to anneal brass but iron or steel won't anneal until the temperature is 1000 to 1500 degrees, depending on the alloy.

"Tempering" is another form of annealing carbon steel or knife grade stainless steel. It usually requires at least three steps. The first is very hot ... cherry red, The second is about 1000 deg F, and the third is about 800 deg F. Once steel is tempered, any temperature under 500 deg F won't have any effect on the steel's hardness. Bluing a tempered carbon steel knife or gun has absolutely no affect on its hardness.

Ruger uses silica in their molds, which helps stabilize the alloy during casting. When Ruger guns are run through the bluing tanks, they come out a very deep blue. With age, (could take several years) the silica starts a chemical reaction with the bluing and turns it "plum". If Ruger washed the silica from the surface of the parts thoroughly before bluing, they would maintain the blue finish and would not turn plum. That's why some guns turn more plum than others .... they didn't get washed as well before bluing. As a gunsmith, I look at this as poor quality workmanship but collectors look at it as desirable. Go figure!
 
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