Hot Blueing info

[fps plus]

I often get asked questions about hot blueing. Here is a little info that maybe helpful.

Hot blueing is a chemical process which is basically an accelerated rusting process. Its chemical causes the steel to turn blue instead of commonly thought of red .The blueing salt are taken to a saturation rate as to boil at 300 degrees Farenheit. The main chemical in the blueing salts is sodium hydroxide.Its nasty stuff and eats anything organic . Treat it with respect and use the necessary personal protection equipment .

Cast Iron will not turn blue ie Post 64 94 Winchesters ,single shot shotguns etc. They will turn a purple hue.
Aluminum will be eaten by the salts and cannot be blued .that's why they are anodized ,painted or some other type of coating applied.

O/U and SxS shotguns should not be hot blued as the blueing salts eat the solder that holds the ribs on and the barrels together . Its not the heat its the chemical reaction between the salts and the solder.

The temperature is not hot enough to cause and metallurgical problems .

All the finish types go into the same tank . Matte finishes are sand blasted or bead blasted and mirror finishes like Weatherby MK V have all scratch marks polished out, all go in the same tank .It's the prep work that determines the type of look you will get . The actual time the firearm stays in the bluing salts is usually 10-20 minutes. Its all the preparation work that takes all the time.

Blueing is a rust inhibitor it can still rust . With a little care its a pretty darn good finish and looks good in my opinion.

[Norwest Alta]

Thanks interesting.

[fps plus]

I forgot to mention that stainless steel can be blued but it requires a different type of blueing salts and can only be used for stainless steel so most don’t bother with it .

[Dean2]

Do how do your re-blue SxxS and O/U shotguns? Asking cause I might want to get one done. Thanks.

[fps plus]

Either hot water rust blue or fume blue basically the same thing the hot water just accelerates the rusting process

[leeelmer]

Originally Posted by Dean2

Do how do your re-blue SxxS and O/U shotguns? Asking cause I might want to get one done. Thanks.

Slow rust blue. or some are slow browned.

[Pathfinder76]

I have a friend that is a classic gun builder. He broke into the industry as a stock maker and rust bluer. He builds complete custom rifles that sell for north of 30k and they are hot caustic blued. Done properly he claims it is the best finish available.

[260 Rem]

I have thought about having barrels hot blued, but shied away with the understanding that the bore might also get the treatment? When I asked about blocking it off, was told the heated air in the bore would push plugs out? So, is it possible to isolate the bore???

[Sashi]

A vented plug should solve that problem.

[fps plus]

Originally Posted by 260 Rem

I have thought about having barrels hot blued, but shied away with the understanding that the bore might also get the treatment? When I asked about blocking it off, was told the heated air in the bore would push plugs out? So, is it possible to isolate the bore???

No you can’t plug bores

Many years ago I read an article while at gunsmith school and the jist of it was the military had found that blued barrels showed a little better barrel life and no degradation of accuracy. I never seen or heard of anyone having issue with the bore of their rifle because of it being blued .

[Dean2]

Originally Posted by fps plus

No you can’t plug bores

Many years ago I read an article while at gunsmith school and the jist of it was the military had found that blued barrels showed a little better barrel life and no degradation of accuracy. I never seen or heard of anyone having issue with the bore of their rifle because of it being blued .

I can't imagine it would take very many shoots to completely get rid of the bluing anyhow. Seems to me it wouldn't survive long given it is pretty easy to scratch the outside of a barrel.

[fps plus]

I m not sure what 260s concerns are . But there are millions of blued barrels out there.

[260 Rem]

Originally Posted by fps plus

I m not sure what 260s concerns are . But there are millions of blued barrels out there.

Millions of barrels don’t shoot threes, or fours,or fives.... I just can’t imagine how “rusting” a bore which has been carefully bored, honed, lapped ... maintains integrity?

[fps plus]

Originally Posted by 260 Rem

Millions of barrels don’t shoot threes, or fours,or fives....

I’m not minimizing your concerns
Is your barrel chrome moly?

And there are plenty of chrome moly “ match grade “ barrels that are blued

[260 Rem]

Originally Posted by fps plus

I’m not minimizing your concerns
Is your barrel chrome moly?
And there are plenty of chrome moly “ match grade “ barrels that are blued

I have had 40+ barrels chambered over the past dozen years most of which were SS. However, at least 1/4 of them (all those under a #3 Kreiger contour) that I use on hunting style rigs are chrome/moly. Whether a real factor or not, I have shied away from getting them hot blued because I am not willing to the potential risk that accuracy could be degraded by the blueing inside the bore. Most of these barrels are quite capable of consistent 1/2 MOA performance so any messing with that would be noticeable. I have just been painting the outside of those I use for hunting with Endura. SS barrels that are used at the Range only stay shiny.

[fps plus]

260 I won’t critiise your concern.
If I were you I would contact Krieger and ask them their thoughts .

All I can give you is my experience and I have no idea anymore how many rifles I have built for myself and customers in chrome moly configuration and they have been hot blued ( a few rust blue and a few nickel plated) I personal have no concerns about the bore being hot blued and do not feel accuracy is being effected

I guess the only way to know 100% would be to test a rifle before being blued and after being blued

Maybe we should try it sometime

[260 Rem]

I would assume the copper would need to be completely removed from the bore before the hot blue?
Wonder if filling the bore with (cured) silicone would keep the chemicals out?

[fps plus]

Originally Posted by 260 Rem

I would assume the copper would need to be completely removed from the bore before the hot blue?
Wonder if filling the bore with (cured) silicone would keep the chemicals out?

Yes the copper needs to be cleaned out. I would have reservations about the silicone.

Your best bet if you want a blue barrel and none in the bore is a rust blue ..The bore would be plugged to do a rust blue.
I still personally would not be concerned about hot blueing the bore but of course they are your firearms . Heck I won the Frank Leffingwel shoot with a blued bore a bunch of years ago

[Skytop B]

Originally Posted by 260 Rem

I would assume the copper would need to be completely removed from the bore before the hot blue?
Wonder if filling the bore with (cured) silicone would keep the chemicals out?

Your going into a +/- 290F caustic bath for 20-30 minutes, that would not work. You would just contaminate the bath and ruin the blue job. If you were to plug the bore the air inside will pressure up and blow 300F solution that is highly caustic. Not very healthy to get yourself sprayed with that hot solution. The bore does get plugged for slow rust blueing though, a completely different process. Old side by sides must be slow rust blued because the heat from hot caustic process will melt the old soft solders, then your shotgun barrels will come out of the bath in pieces lol

[260 Rem]

Yes, I was aware of the plug/expansion issue hence my question regarding filling the bore with silicone. Did not think about the potential for contamination.
I guess another option would be nitriding ... maybe a way of doing that to outside surface only?