It is pretty well explained in Larry "the x-con" Wilsons book "Ruger, the Man and His Guns.............."
bottom line it's , in the case of the Ruger, a "casting issue", the "mix ( or they call it the batch) is made of of a bunch of different metals to attain the "proper" engineered alloy of 4140 Chrome-moly steel that is common for use in making firearms...Ruger has been doing this on their own for many years, and have it down "pretty" good for the MOST part.BUT once in a while the batch may be not thoroughly mixed or when pouring the mix into the mold, the use of silicon was/is used to aid in the "mixing /flow of the material into all the creases and crevices...anything out of "spec" ( too much , too little...) will affect the outcome of the metallurgy and its properties...now come time to "blue" the parts and if there are " hot or cold spots, streaks,etc, the blue will come out a different color in these areas... just as heat treat ,(hardness) can affect the bluing, so does the actual metal itself....now, Ruger collectors tend to find this "color" hues variations "nice, cute ,pretty, different" what ever, BUT it is still a "boo boo", a flaw, wrong.... these same colors can also be gotten by improper temperatures of the salt bath ( bluing solution) and also by not leaving the parts in "long enough" and when this occurs with ANY other gun company ( for the MOST part) they reject it or reblue it.... this is also quite common when 'outside' sources reblue any firearm and they are NOT "good at what they do", this is often a sign of a "reblue", so it is a "catch 22"....no WBR never threw anything out nor "wasted it",thats why years ago , in the beginning they even offered to "redo" any firearm "free" for the owner, a letter was put in the shipping carton ( box) along with the firearm ( maybe Flatgate will post that "neat" picture of the original 'letter from Ruger.......)
Problem is MOST firearms ' "experts" ala Winchester, Colt, S&W and others, do NOT like to see this "plum" and will pass up on buying any of the guns that have this as I said, it is "wrong" ....not desireable to any of those makes and models....ONLY the Ruger collectors get off on this...and yes, it is "nice,cute, different" as all humans are....yes, I even take a liking to it myself....BUT having been in the refinishing business since the late 60's, we KNOW it's "wrong" and would NEVER put out a job that has this....by the way, if it is in fact , in the metal makeup, and you do a proper "reblue" job, it will usually again "turn plum" or "streak".........
yes, you can at times address this by upping the temperature range but this is NOT good for your 'salt bath" we used to save doing the nickel steel guns and such towards the end of the "bath life" as they will ruin ( kill the bath) so the old 'nickel steel ' Winchesters went in "last" and yes, they would come out and stay "blue" for the most part, as will any of the Ruger metal parts...........................
This is a simple ,easy explaination, nothing "technical", as I am NOT a metallurgist,nor do I even LIKE to use/play/work with ANY "salt bath" makes MY skin crawl, and get itchy all over.......I do the prep and final fit , all the "hard" stuff, and leave the "cooking" to the 'chef'......... :roll:
and to answer your question, YES, even today , once in a while you will see parts at times that have this "color" makes no matter the model either.
