A past Mark X advert says, "forged and machined from high carbon, manganese alloy steel".

Anybody know what that would translate =/- to in AISI or SAE?

In AISI high carbon is about 0.60 to 1.00% carbon.

I wonder if that high carbon bit is correct?

It is just marketing; it does not mean high carbon the way we know it. They are very strong actions though.

Yeah it is funny how so much bad info is out there on the basics.
Like what a receiver is made of or how it is heat treated.

Like the Dumoulin Sarco Chinese/Belgian air hardening steel.

I am reading Rodger Rule's book on the Win model 70, says the pre 64 receiver is made from 4140 and hardened at 1200-1300 F in a salt bath achieving 47Rc.
With the extraction cam spot induction hardened.

That listed temp doesn't seem hot enough to conventionally Q&T or even for case hardening using the gas nitriding process.

Do pre 64s receivers have a case or are they through hardened?

Reading between the lines, I am deducing the rear extraction cam was spot induction hardened and the receiver ring or some portion of the front was case hardened using gas nitrating, but at higher temps.

Can anyone offer a basic tutorial on action steel types and hardening methods?

No Winchester 70s are case hardened at all; in fact 4140 is not a good steel for that, too much carbon in it.
I could do the lesson.....if I had time.
Rifle receivers work both ways; look at the 1903 Springfield and you will see; early ones were case hardened; work fine. Later ones were nickel steel, and quite soft but tough; work fine, Latest ones were 8620 and case hardened again; work fine. More than one way to skin the cat.

quote:

Like the Dumoulin Sarco Chinese/Belgian air hardening steel.

What was meant by this reference, I didn't understand where you were going with that?

quote:

Originally posted by Snellstrom:

quote:

Like the Dumoulin Sarco Chinese/Belgian air hardening steel.

What was meant by this reference, I didn't understand where you were going with that?

From sarco's website, RECEIVER: This is an A-2 steel, forged / heat treated body

^Doubtful.
There is a thread here somewhere on the subject.

quote:

Originally posted by dpcd:
No Winchester 70s are case hardened at all; in fact 4140 is not a good steel for that, too much carbon in it.

No, not case hardened in the conventional sense.

Nitriding in a salt bath, it is done at lower temps than Q&T and creates a hardened surface and less warpage.
https://en.wikipedia.org/wiki/Nitriding


I don't know that is how Winchester did it, I am guessing given the info in Rule's book.
A salt bath, lower temps, way below what is required to transform the steel, no quench and the extraction cam induction hardened as a separate step.
^ If it was just plain old Q&Ted to a uniform 47 Rc, why do the extraction as an additional step?

I am picking up some 4140 for my receiver blanks today, I will see if I can talk to the metallurgist there and see what he says.

quote:

From sarco's website, RECEIVER: This is an A-2 steel, forged / heat treated body ^Doubtful.There is a thread here somewhere on the subject.

Yes I am aware of several threads that mention those actions but if you read those threads there is a lot of posturing and conjecture not a lot of facts.
Opinions on those actions run pretty far apart from junk to fantastic and not much in the middle.
That's why I didn't understand your reference.

A-2 is air hardening tool steel. We use it to make punches and dies, used in a punch press, for forming parts from 12g sheet steel. Don't know how the material would be for rifle actions. 4140HT is pretty hard to beat for the money, for a rifle action. A-2 is rather an expensive tool steel.

quote:

Originally posted by Snellstrom:

Yes I am aware of several threads that mention those actions but if you read those threads there is a lot of posturing and conjecture not a lot of facts.
Opinions on those actions run pretty far apart from junk to fantastic and not much in the middle.
That's why I didn't understand your reference.

The reference is, that even with recent production like the Sarco offered Dumoulin we really don't know where it was made (Sarco doesn't say) or really what the receiver material is, since A2 would be a very odd choice.

4140 already has .4% carbon in it so doesn't need any more to make it any hardness you want; it is the tempering that brings it back down to a usable softness.. Winchesters are not very hard, which is why they induction the extracting cam in a separate operation.
Also which is why you don't "case harden" it; don't need to add any carbon to the case.
But Turnbull can "color case harden" it; producing nice colors and little hardness. If you want to CCH a modern steel, use 8620.

quote:

Originally posted by dpcd:
4140 already has .4% carbon in it so doesn't need any more to make it any hardness you want; it is the tempering that brings it back down to a usable softness.. Winchesters are not very hard, which is why they induction the extracting cam in a separate operation.
Also which is why you don't "case harden" it; don't need to add any carbon to the case.
But Turnbull can "color case harden" it; producing nice colors and little hardness. If you want to CCH a modern steel, use 8620.

dcpd, did you read the nitrating link?
It doesn't add carbon, it adds nitrogen.
Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface. These processes are most commonly used on low-carbon, low-alloy steels. They are also used on medium and high-carbon steels

Examples of easily nitridable steels include the SAE 4100, 4300

And according to Rule's book, Winchester experienced chipping on the bottom receiver ring flat, when it was stamped with a inspectors mark because it was so hard.

But I suspect the rest of the receiver was unhardened.
^ Correction, it must have been all hardened or nitrated because it was hardness tested at the tang.

OK, I am home and dug out Rodger Rule's Book The Rifleman's Rifle. I guess THE BOOK on the Model 70.

From page 52&53.




So I am not sure what all is wrong.
But to heat treat 4140 conventionally requires a temp of 1525-1600 degrees F.
Then an oil quench.
Then tempering at about 700 degrees F to get to 47Rc.

But that isn't the procedure that Rule listed.

Where as nitrating is done at a lower temp somewhere around 1100 Degrees F.
No quenching.
No tempering.

Additionally the steel can be hardened 1st conventionally, then nitrated so the core can be softer yet still hard.

The process Rule wrote is closer to nitrating than conventional Q&T so I am guessing that is what Winchester did.

I was going to ask a bunch of those questions to the metallurgist yesterday, but he has moved on and they haven't found a replacement yet.

More info can be found here.
https://www.steeltreating.com/gas-nitriding.php
https://www.asminternational.o...007P33&groupId=10192

Yes I have that book and I know what nitriding is.
I was just saying that the conventional case hardening process can't be used on 4140.

Well a ghost from AR past has whispered to me that Zastava used 6140 a medium carbon Chromium-vanadium steel.

It isn't 'high carbon' by AISI standards but it looks like it would be a very good choice for a receiver.

t’s commonly used in heavily stressed machinery parts including shafts, gears, pinions and also in hand tool components. ASTM 6150 steel is also widely in the motor vehicle industry AISI 6150 is suitable for many general engineering applications that require high tensile strength and toughness.

6150 seems to be the closest we have in the US, and doesn't seem available from most steel suppliers, especially compared to the availability of 4140.

Thanks for all the information in this post, esp DPCD.

Taking a nap on El Capitan at 2,000' level. Kind of minimalist attire. I dug my climbing shoes (Adidas running shoes) out of my haul bag when the afternoon heat subsided a bit:

Consider your choice of a bed, I doubt that I would be at all concerned about gun steel or even a lead barrel, ya ain't going to be around long enough to worry about it if you have a nightmare!