Now and then I see a custom rifle with a bright but pale blue part, usually a Mauser/Mod 70- typelong extractor. I have a question for youse smart guys.

Is this a heat treatment or a chemical process? Or both?

Thanks.

Heat treatment, or tempering colour.

Heat. Brownells has the salts.

I have heat blued a lot of parts like screws and sights. You have to limit it to parts that won't be affected by temps up to 500 degrees; the chart above shows that. Msuser bolt stop springs are a popular blue item.
The technique is to polish the part, and heat it, BUT, DO NOT heat it until it is blue; if you do, it will keep on turning colors and seconds later you will be looking at a gray part because the blue color will disappear. So, heat it slowly and sneak up (technical terms here), on blue. then stop.
Oil. I have also quenched in oil, but that is smelly and messy and not necessary. You aren't heat treating it, you are just coloring it.

I've used Express or Belgian blue on parts. takes longer for the water to boil than it does to blue the parts.

boil water

dunk
coat with chemical
repeat as desired.

The light color shroud is the same bluing as the bolt handle..but the shroud is probably harder steel. (pilkington every 4 hours and boil in between. about 4-5 times)

The other shrould looks like it's not done. Herters type belgiam express blue. takes about 15 minutes.

Just to avoid confusion, the answer to the OP’s question has nothing to do with any kind of rust bluing.
The blue colour on extractors etc is produced by heat, usually by Potassium Nitrate salt bath.
But polished steel heated by any means to 555 deg.F will turn blue.

Thanks- I'll try it.

I've rust blued several barrels with good results. I assume the heat treatment does nothing for rust prevention.

No, heat bluing is still bare steel and has to be oiled.
Here is a North West Trade Gun that I built (built as a .58 cal rifle because I have no use for guns), with a heat blued lock. It has faded a bit. Note the Fox, a feature of NW trade guns; the Indians liked to see those.

I don't mess around with Nitre bluing salts anymore, I can get a nice blue on screw heads by careful heating with a propane torch. It takes less than 1 minute.

If you want to do critical parts like extractors, springs and larger parts then by all means use the salt bath method.

Nice.

I've had good success with heating small parts in a ladle sitting on top of my lead melt in my lead pot.
I have a PID temperature control on my pot and I find that I can get better color control with multiple small parts at one time.

That's all pretty interesting, especially metal's screw heads. Going to try it. Learn something every day. Well, some days.

Ive seen barreled actions with a "light blue" rust blue, a silver blue like the old REm 721 and 722 and it last forever..I recall a well know bluer who gives you that option, well I don't recall but his name starts with a W dammit he does wonderful work at about $300 or there abouts.

I really like that browned barrel's contrast to the lock!

quote:

Originally posted by dpcd:
No, heat bluing is still bare steel and has to be oiled.
Here is a North West Trade Gun that I built (built as a .58 cal rifle because I have no use for guns), with a heat blued lock. It has faded a bit. Note the Fox, a feature of NW trade guns; the Indians liked to see those.