What is going on with this P320 metal heat treatment/tempering/rainbow?

Wow...regardless, they did a **** job with the finish didn't they?

TiN finishes do that with micro differences in the thickness of the application. Dye is added to make it black and that seems to be why it happened - not quite enough black. TiN is done at some elevated temperatures but it's not done to make the gunmetal super hard. Functionally it's ok, entirely up to you whether its satisfactory. In the pic it wont show assembled and as it breaks in it may turn steel colored shiny.

The subject comes up now and again, I've yet to find any specific heat treat regimen for ordnance steel. The treatment of knife alloys is common, or anodizing and forging platters, but there's not much heat treat of gun parts cause they get hot enough to lose temper. Mag dumping M16's in combat until they smoke wouldn't go well if they were then brittle when the gun was fired cold - no reports of that over 45 years and plenty of wars.

Does the gun still function?
Is it a tool or a piece of art?

Why can't it be both? Life is too short to have an ugly gun.

Sig is just being inclusive with rainbow colored guns😆

SpartanGoat said:

Why can't it be both? Life is too short to have an ugly gun.

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If you want it to be both, you likely need to be buying a fancier gun that costs more.

hauki said:

Sig is just being inclusive with rainbow colored guns😆

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The new pride month edition.... Another SKU for Sig's catalog

Wouldn't bother me but it's your gun...

raz-0 said:

If you want it to be both, you likely need to be buying a fancier gun that costs more.

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I have a P320 AXG Pro that I have customized and I think its beautiful. : ) No need for a $4K gun to look great. ; )

bblr said:

Does the gun still function?
Is it a tool or a piece of art?

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I doubt the OP's main concern is what it looks like. It can't even be seen when the gun is assembled. I think he's wanting to make sure the heat treatment was done properly and not defective, a very important point for any tool, especially one with high pressure explosions.

Well it's a new gun so I'd contact Sig . You paid for a gun that was properly heat treated with a Nitron finish not a gun with a 97% Nitron finish. Admittedly scratches don't really bother me but I prefer I put them there, you paid for a 100% brand new gun and that's what you should receive. Good luck.

The is stainless steel.
The rainbow color you see on the invisible interior surfaces of the slide are a result of the process used to apply the Nitron treatment to the stainless steel. Believe it or not, virtually every Nitron treated stainless steel slide from SIG has SOME spot, or area, where that is seen. Especially where the mount that holds the slide during the Nitron treatment.

If you search the site, and others, you will find this discussed over and over and over......

This is perfectly normal, nothing wrong, just an artifact of the heat-treating process.

As parts go through heat treatment, they must sit on something. This something tends to draw some heat from the part, hence the discoloration. Heat treaters will design special racks, if the application demands a cosmetic outside appearance, such as a handgun slide. These racks happen to contact the slide in a nonvisible area when the slide is assembled to the frame.

It is very common, nothing to worry about.

Now shoot it like you stole it!!!

SpartanGoat said:

Wow...regardless, they did a **** job with the finish didn't they?

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Nothing wrong with it!

It was mentioned earlier in the thread that this is a TiN (titanium nitride) coating. The treatment on your slide is called Nitron by SIG; the finish results from heat treating, not a deposition coating such as TiN. I see many firearm parts being TiN treated in the aftermarket; some come OEM with TiN. However, I am unaware of SIG ever applying a TiN coating to their Nitron slides.

OK that makes sense, however I will say that I have handled, cleaned, or shot over 50 different P320's and I have never seen anything like this before. Nor have I seen it on any other Nitrided component before. It looks unusual.

tango44 said:

Nothing wrong with it!

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It's supposed to be black. It's not black. Functionally it might be fine, but you can't say nothing is wrong with the black finish when its not black.

If I look closely at that area on my P365 slide, there is some similar coloration, but its not as pretty as yours. Doesn't bother me a bit.