Gloria a Dios I have been gifted a cracked M12 Winchester Proof Steel barrel

Here is the previous thread regarding Winchester steels
https://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=561800&page=1

Most sources state that Proof Steel was 4140 (including Mike Hunter and Ned Schwing)
Winchester catalogs in the 70s state Proof Steel was “cold forged Chrome Molybdenum”.

Other internet sources however state “nickel-chrome-moly alloy steel”.



There is a '37' at the breech - does this mean 1937 DOM?

The crack at 17". There is a slight ring bulge there. The MWT is an impressive .072"! Bore is .732".



The barrel has (presumably) been cut to 25 1/2" and threaded for a choke device/Cutts?

I couldn't quite capture the marks on the external surface opposite the crack. Possibly where someone tried to pound down a bulge?



And THIS is the bore at the site of the crack. I could not get the camera to focus on what appears to be 2 annular rings/dents?





I would very much appreciate the thoughts of those here.
Is it possible that someone tried to use a hydraulic dent raiser, bulged and cracked the barrel, then tried to pound down the bulge??

So the muzzle end segment is off to METL next week and we will KNOW if Winchester Proof Steel is 4140!

Just conversation Doc Drew. If the scenario started with a dent, what might create apparent multiple dents, around the circumference, at a common distance down the bore? Maybe, it was fired with a obstruction, unrelated but possibly a reason why it ended up so short?

I didn't explain that very well. The annular dents now evident in the bore are outward from the bore, as if a pilot or hydraulic dent raiser was expanded.

The anvil of a hydraulic dent raiser would only exert force upon a small portion of the circumference. But you might consider the possibility of a different type of hydraulic forces at play. I'll toss out the THEORY that this damage could be the result of an excessive amount of grease or heavy oil in the bore when it was fired. I see a less prominent annular ring bulge beyond the two larger rings, so this might be an extreme example of rivveling.

What is rivveling?

jlb

I posted a couple of slightly better images.

Rivveling - A series of slight ring-bulges or wrinkles
https://www.pressreader.com/uk/clay-shooting/20190403/281827170117384

Regardless how your assay turns out Drew, you aren't going to prove anything with a sample size of one.

I thought it was generally agreed that the WP stamp simply indicated that the steel used in the product so stamped was, in the opinion of Winchester, simply the 'best' steel for the application.

'Winchester Proof' was used on a great many products over many, many, years it's difficult to imagine it represents a particular alloy.

Shotgunjones-

I agree that statistical methodology requires multiple samples to provide statistically significant findings that can be used to speak authoritatively about the object [or subject, or group, or event] being evaluated.

That said, I also thoroughly believe that a scientific examination of a sample of one gives more insight than an examination of zero- which allows us to speculate without any shred of evidence to point in any direction.

I have never poured steel. I don't know how often the alloy of a steel firearm barrel is changed, while it keeps the same name.

It seems just as likely to me that they would keep a formulation that began with them clearly demonstrating that it was able to digest the 'blue pill' loads without a hiccup.

After such thorough testing to proof how strong it was, it seems that they would try to keep the same alloy, so that the barrel would stay as strong.

But, again- I am just guessing from a sample of zero.

Does anyone know one way or the other if the 37 refers to the year made?

I seem to remember reading that elsewhere as well.

As an owner of more than one Model 12, I am definitely interested in the outcome of this.

Even if I understand that the sample of one doesn't mean EVERY barrel is exactly the same- it gives more info than it did before.

Just need to find more donor barrels...

It's not related to metallurgy, but there is some thought that a single firearm or barrel failure can be analyzed for the purposes of arriving at a definitive conclusion. But, speculating can be interesting?

As far as why it cracked, I think you're on the right track about a bulge being hammered out and the material becoming work hardened.

This one fared better than the one my pal blew up on New Years Eve 40 years ago. Old shells, a dud, he racked in a new one with the usual results. It split down the side. Proof Steel, just not idiot proof.

There seems to be comment about a known ring bulge, and at the same time we're thinking that there were inward dents at the same location on the barrel? I'd speculate that what ever caused the ring bulge, might not be ruled out as the cause of the crack?

Those dents don't seem to reflect on the outside of the barrel. Due to the appearance of the patina, maybe there was some striking and refinishing in the distant past? Though it appears pushed outward, could the 'dents' be formed by uneven tapping down of a bulge? Could the crack have formed or showed after a fair amount of use, time and wear passed?

The ‘37’ is definitely the year of manufacture of this barrel, with Win Proof Steel being introduced in 1932, the year John Olin took over. I always thought replacing the nickel steel barrels was a cost cutting measure. The date stamping on barrels gradually stopped post WW2. Regards, Sandlapper

Thank you sandlapper.

SGJ: I don't understand.
"Winchester Proof Steel" was the name given by Winchester when introduced in 1931 for the Model 21 and in 1932 for the Model 12.
Ned Schwing states it was 4140.
Winchester catalogs in the 70s state Proof Steel was “cold forged Chrome Molybdenum”.
Certainly within a pour there can be slight variation in composition, but 4140...is 4140.
Have you read that Winchester at some point changed to a different steel?

Craig: there is a ring bulge. The defects I'm calling dents look like 2 annular furrows and are OUTWARD from the bore into the wall, but don't show on the external surface of the barrel; which does show what looks like brass hammer marks as if someone tried to pound down the bulge. I can't be sure that the pin of the wall thickness gauge is in the bottom of the furrow in order to accurately measure the wall thickness, but it is obviously less that the barrel just proximal and distal to the defects. The crack is perpendicular to the furrows however.
I'm only guessing that maybe what started all this was an inward dent that someone tried to raise, which caused the inside annular "dents" and bulge. Work hardening is a good thought.

The barrel segment is off to METL this am.

Possibly a gunsmith could comment: Is there some device (pilot, mandrel, dent raiser) that could be expanded with such force as to cause the 2 annular furrows? Thank you.

I ask because of this: A 16g victim of chamber lengthening with four 1/4"-3/8" circumferential bulges, with a surface crack.



corresponding to four end of the forcing cone dents; which I presume to be from the reamer pilot?

In my opinion those marks look about the same size and shape as the anvil on a hydraulic dent lifter. Those things have a lot of force and take a delicate touch to not go from a dent to a bulge.

Thank you. To clarify, I am asking about these annular furrows in the Model 12 barrel which are associated with a ring bulge

Wasn't it more of a way out of the Stainless Steel debacle?

Seventeen inches down the bore, would there be a tooling pilot positioned at that point? The barrel thickness seems generous in that area, maybe tooling damage might appear as material loss before outward displacement? Grease has been mentioned, how about some mud or snow contributing to a ring bulge?

360 degree damage from a hydraulic barrel dent remover???

C'mon... even a gunsmith who supports anti-gun Liberal Left Democrats isn't that stupid... I think.

Notice the multiple small outward bulges, they could easily be from a hydraulic dent lifter, used in several different positions around the outer diameter of the barrel.

Even someone as biased as yourself should be able to see that Billie kEITH, unless you are just too stupid.

Well Stevie, when I hoped that even a gunsmith who supports anti-gunners wouldn't be stupid enough to do that sort of damage with a hydraulic barrel dent raising tool, you must have known I was thinking of you. I see my post struck a sensitive little nerve.

Fact is, if you took a moment to remove your head from your ass... a close look at those marks shows that they are not all the same... as they would be IF the same hydraulic dent raising anvil had been rotated around the circumference of the bore.

Furthermore, when have you ever seen a barrel dent that went 360 degrees around a shotgun barrel, and would require 360 degrees of rotation around the bore? And what kind of idiot... besides you... would make a series of bulges all the way around the barrel, after noticing that you had gone too far after one or two tries?

It's pretty easy to see just who is biased here Stevie, and also who is ignorant enough to grasp at any straw, no matter how ridiculous. On the other hand... a so-called gunsmith who farms out as much work as you probably doesn't have much experience raising dents.

I have seen and repaired all manner of damage, usually caused by amateur hacks such as yourself. I can lift dents in my sleep using several methods, occasionally even a hydraulic dent lifter.

The only nerve you hit is that I have tired of your self appointed expert status and will continue to point out when you are mistaken, which is quite often.

I don't have any "self-appointed expert status" Stevie, and nobody here requires "expert status" to know that we just do not see barrel dents that go 360 degrees around a barrel, and repeat that 360 degree damage in more than one location in the bore.

But I'm sure you can show us some before and after pictures of such damage that you've encountered in your vast experience of farming out work to real gunsmiths... while you spend all day here going out of your way to prove your ignorance.

I wish Dewey Vicknair was still here. He'd be laughing his ass off at your silly observation about this barrel damage.

Gee taking dents out of barrels is so routine I do not take pics. I will next time just for you Sweet wILLIAM.

Those are bulges, outward, not dents. You would think a rocket scientist such as yourself would be able to tell the difference.

If you had any intelligence at all Stevie, you would understand that there would not be 360 degrees of outward bulges... made by an imaginary asymmetric hydraulic dent raising anvil, if the barrel had not been damaged 360 degrees around the circumference.

But you don't have any intelligence. And someone who takes the time to post pics of themselves wearing buckle-strap girls shoes would certainly take the time to take before and after pics of this sort of 360 degree dent removing....

Keep grasping at straws. I love it when you show how pathetic and stupid you are.

It is not an even 360 degrees, notice the several small bulges around the barrels circumference.

I switched to the Buchsenmacher air model for summer, 3 buckles is better than 1 I say.

Yeah, we already saw your new 3 buckle gay apparel Stevie. I'm surprised that there is no nail polish on your toenails though. I suppose the nail salons in Colorado are still shut down due to Covid19 restrictions, or you'd be going whole hog with your transvestite look. Your feet are sure rather dainty and feminine though... only spanning less than two of those 5/4" deck boards. Speaking of your deck, did you build that too? I figure you did, considering some of the gaps between the boards are big enough to throw a live cat through.

With skills like that, it isn't surprising that you still don't see that the damage to this Winchester shotgun barrel goes 360 degrees around the circumference of the barrel. And it has already been discussed and established by photos that there is more than one ring of damage. However, you still want us to believe that some fool would continue to rotate an asymmetric anvil of a hydraulic dent raising tool, and also continue to make bulges where there was an extremely unlikely 360 degree series of dents. Perhaps you are seeing smoke rings from your bong again.

But you keep right on grasping at straws, and keep telling us about how you are so busy doing gunsmithing jobs that you have all day to post examples of your ignorance here.

Ok folks, enough of that. Having different opinions to offer to those of us who aren't all that well versed on these topics is great. But I didn't sign on to this forum to "hear" a squabble like this. Take a break and cool off!

Results are in, and I found some additional information

From a 1934 Winchester salesman’s manual reproduced in The Rifleman’s Rifle Winchester's Model 70, p.23:
“Proof Steel. Winchester pioneered the alloy steel field by the production of heat treated nickel steel barrels thirty years ago…”
“Two or three years ago our metallurgists together with those of one of the greatest steel companies in the country, produced a new alloy. This new alloy was a chrome molybdenum steel which was capable of being tempered to a greater strength and resistance to wear, and still be in a machinable state, than any other alloy yet discovered.”
“Winchester decided to coin the name ‘Winchester Proof-steel’ which would be Winchester’s guarantee that it would be the finest alloy steel known at the time.”

The Winchester Model 12 owner’s manual in the 1960s state “Only the finest of gun steels-WINCHESTER Proof (Chrome Molybdenum) Steel-is used in the manufacture of your Model 12.”





Winchester catalogs in the 70s state Proof Steel was “cold forged Chrome Molybdenum”.

Winchester's Finest The Model 21 by Ned Schwing states Chrome Molybdenum alloy.

Mike Hunter has stated specifically 4140.

THIS 1937 Model 12 “Winchester Proof Steel” barrel is non-standard (low chromium and slightly high molybdenum) AISI 4135 medium carbon low alloy steel
Carbon – .34% (0.33 - 0.38)
Manganese - .76% (0.7 - .9)
Chromium - .62% (0.8 - 1.1)
Molybdenum - .30% (0.15 - 0.25)
Nickel - .09% (< .01)

Yield strength – 79,500 psi
Ultimate tensile strength – 107,000 psi
% elongation – 12
(Industrial standard for non-heat-treated 4135: Yield – 75,000; Ultimate – 110,000 psi. 4135 may be heat treated to much higher strength.)

I recognize that Winchester over the years may have specified 4140.
And BTW I was not able to find a definitive statement as to which company made 1930s "Winchester Proof Steel"

I also have no explanation for the internal barrel defects, the ring bulge, and the crack.

Thanks for the data point Drew.

Here is an interesting series of articles about the history of alloy steels. It puts some names and faces to terms we've all run across reading about alloys and heat treating. Part one is easy to find on the net if you're interested.

https://nanopdf.com/download/metallurgy-lane-the-history-of-alloy-steels-part-ii_pdf

This era, the 1920's and 30's, marked the transition of steel making from an art to a science. My dad, who had a hand in making the stuff for Mr. Ford always said that before about 1930 steel was made pretty much by the seat of the pants.

Winchester would no more pay for steel that had properties not actually needed for the task at hand than would any other large profit making company, advertising claims notwithstanding.

There's something to be said for the idea that the change from 'nickel steel' to 'Winchester Proof Steel' was more of a cost saving measure than anything.

General Guy Drewry gained notoriety during WW2 for optimizing the steels used in war production minimizing waste of alloying metals.

My view is that Winchester Proof Steel is just a trademark and applied to whatever did the job the best for a particular application. 'Best' also figures in cost, and cost is not limited to just the price of the raw material. Tooling wear, ease of finishing, etc. figure in.

Is the steel used for a shotgun barrel also used for the barrel of a 300 Win Mag? They both get the trademark stamp.


BTW: The assay shows .09% Ni, which is pretty close to .1% (instead of <.01%) and not negligible. 4135 maybe, but with added Ni.

1933 Model 21 catalog included the 115,000 psi tensile strength figure for "Winchester Proof Steel", and this



7.5 long tons = 16,800 psi + 10 - 14% for modern transducer number. 16,800 + 1,680 = 18,480 psi. Modern SAAMI proof load standard is about 19,000.
5 long tons = 11,200 psi + 10 - 14%

SGJ has a good point regarding the low concentration of nickel content - it was no doubt on purpose.
4340 has .7 - .9% Cr and 1.65 - 2% Ni
4330 .4 - .6% Cr and 1.0 - 1.5% Ni

The figure of 115K PSI ultimate yield would seem to split the difference between 4130 and 4140 and makes sense.

Was this material then used as received from the mill without further heat treat?

That would seem to be the advantage over a simple steel like 1080 which would need a good (and costly) heat treat to achieve a high tensile strength.

The same catalog states that the frames were heat treated "to a tensile strength over 90 tons per square inch. This is far better than the usual case hardened frame." 90 long tones = 201,600 psi (possibly a bit of marketing hyperbole!)
There is no mention of heat treating the barrels

Edwin Pugsley in a letter to F.W. Olin April 11, 1932
“Both (Model 21) frames were heat treated, then one was case hardened and the other blued. The case hardened frame had a tensile strength of 94,200 psi, an elastic limit of 85,400 psi, and elongation of 2%. The blued frame had a tensile strength of 174,600 psi, an elastic limit of 160,950 psi, (and) an elongation of 12%.”

By the late 1920s AISI 1040 was fairly standard for U.S. maker's double's barrels; including Crescent. Frames were 1020.

Resulfurized AISI 1137 (“gun barrel steel”) & 1144 low alloy carbon steels are commonly used for modern shotgun barrels and are easily machined. 1144 has an industrial standard tensile strength of 108,000. Neither would have the corrosion resistance of 4140.

Could this just be that Winchester specified 4140, and this batch of steel happened to spec a tad off from book numbers? Isn’t the tensile strength of modern 4140 under a 100K? If the batch came in and someone at the factory did quality control performance checks, wouldn’t this alloy have passed. Would it have been worth Winchester’s time and resources to demand .05% less carbon and a pinch of nickel?

Yes Craig. The industrial standard for non-heat treated 4140 is 95,000 - 100,000 psi.
I'm only guessing but assume Winchester got pretty close to what they requested; and all the literature/ads state "Chrome Molybdenum", not 4140.

Interesting reading. "Blast Furnace and Steel Plant", July 1921
https://books.google.com/books?id=1dwfAQAAMAAJ&pg=PA426&lpg

Drew do you have any definitive reference on exactly when the AISI nomenclature actually began?

Best I can find is a vague 'early 1940's'.

Hatcher in 'The Book of the Garand' which was written in 1948 refers to 'WD' (War Department) specified steel number codes.

He states the barrels were 4150 Modified, early receivers 3115, early bolts 3312, with a standardization after 7-42 to 8620 for both receivers and bolts.

This is interesting because the M1 started production in 1937.

Winchester made half a million or so Garand rifles under contract so at that time they were working with 4150, or a version of it close to the commercial grade.

The war department found 4150 necessary for .30-06 barrels of the period, at least those used in semi-automatic rifles. It is still used today by various barrel makers.

I wonder what Winchester settled on for the magnum calibers in their sporting rifles.

With the 1933 National Industrial Recovery Act the American Iron and Steel Institute began publishing “Steel Products Manuals” with the “Steel Code Tables”. The Society of Automotive Engineers also published a “SAE Handbook” with a similar numbering system, and in the early 40s the tables became the SAE-AISI Code Designations.

I've got a little about vintage rifle barrels starting on p. 35 here
https://docs.google.com/document/d/1dnRLZgcuHfx7uFOHvHCUGnGFiLiset-DTTEK8OtPYVA/edit

Up front, I will state I know little of the science of steel, steel types, alloys, ect.
But I do find most of this thread interesting anyway.
As an engraver that has cut many Mod 21 and Mod 70's I can add this if it means anything.

The Winchester (original) 21 frames are (heat treated) so that they were as tough as most anything you would care to cut with a hammer and chisel.
They file, drill, and mill cut with little noticable difference from other steels that you run up against.
But attack it with a chisel,,and it will easily break the points with regularity over and over again.
Resharpening sometimes every minute is not uncommon.

Use of carbide gravers helps immensely, but even then they get battered and shatter the point as well. A carbide point is a bit different in the way it breaks as it can still leave you with a raggedy sharp surface. So sometimes the engraver just keeps going, but it shows.

Use of an air-assist engraving tool further prolongs the point life in the cutting of the frame alloy. The ability to adj to a much lighter 'strike' but yet rapid rate can make the work at least progress at a seemingly acceptable pace.

The toughness of some of the frames was so tough that when trying to do inlay work, the slender inlay punches would just turn over when struck. When reshaped to a stronger angle, the frame alloy wouldn't play along. Instead of under cutting by the punch, the alloy would chip off those thin edges.
Frustrating.

The trigger plate on the M21 I'm told (I don't know for a fact) is of the same alloy as the frame.
That trigger plate is as soft to cut as CRS.
Absolutely no problem in working on that part.

But the frame, toplever, forend iron,,all fight you all the way to the end.
...and they are not consistent in their toughness. Some are tougher than others and some quite noticably easier to cut.
M21 bbls are tougher than most other mfgrs bbl material. Not anywhere near what the frame is, but not as soft as the trigger plate of the 21. Nor as soft as say a set of Fox or Parker Bbls.

The M70,,the recv'r is as hard or nearly so as most M21's in the front recv'r ring back to about 1/4 to 1/2" beyond the ring itself. Then it gets noticably easier to cut.
Spot/area hardened?
Even the WP proof mark stamped in that area is usually weak on that harder surface than the one on the bbl right next to it.

...and FWIW, the M42 frame is a little tougher than the M12 as far as how it feels when you engrave it with hammer and chisel.
The Magnum rec'vr of the M61 is also that way when compared to the M61 s,l,lr. Not a big difference in each,,but noticable.
I'm guessing the same alloys used and just different HT,,but as I started out,,I'd just be guessing.

Thanks Drew.

Hatcher has a slightly different spec for 8620.

He claims, for WD 8620:

C .18% to .25%
Mn .70% to 1.00%
Ni .20% to .40%
Cr .20% to .40%
Mo .15% to .25%
S .07% max
P Not over .04%

I knew that that with the advent of smokeless powder rifle barrels had to be toughened up to resist erosion.

So, in 1931 Winchester couldn't just ring up Midvale or Crucible and say 'send us a car of 4135', right? That would have come maybe as much as a decade later?

Thank you Kutter

I suspect the metallurgists and chemists at Winchester specified exactly what they wanted, and got pretty close to it. This was pre-Optical Emission Spectroscopy
It would be very interesting to find purchase orders or invoices from the introduction of Nickel Steel (and esp. for the short lived M12 Stainless Steel) to the 1960s to find out.

Thanks for taking the time to comment kutter. It does seem to point to a tendency, but somewhat lack of consistency.

I'd say that kutter's thought that heat treating makes a world of difference in the same grade of steel is 100% correct. I've had hardened steel that was near impossible to drill without destroying a HSS drill bit that cut almost like cheese after annealing. Maybe someone would like to anneal a Model 21 action or Model 70 receiver to confirm it.

Just food for thought keith, and I'm not trying to misrepresent any of Kutter's thoughts. The receivers seem to mill and file just like any other steel?

Maybe, tight tolerances and material handling weren't really critical to ending up with a decent Winchester. It's possible that they specified steel that met a minimum performance in the face of potential mill and manufacturing shortfalls?

I think it would really depend upon the type of heat treatment that was given craigd. What might not seem to significantly deter cutting with a 10" mill bastard file or a stout milling cutter might easily dull or damage the fine engraving tools kutter is using. But the exact same steel that was hardened, but not drawn, might be very difficult to file or mill. The metallurgical CHEMICAL analysis of a sample of steel is very important, but does not tell us everything. Different heat treatment can make a huge difference in machinability and performance. The exact same grade of steel might bend, flex, or shatter like glass, depending upon annealing, hardening, and tempering. You can experience all of the above while learning to make springs.

My thinking was that if two different receivers of similar steel composition was subject to different heat treating, which would be an unfortunate inconsistency in itself, then a graver tip would likely feel different but consistently different. When resistance and tip breakage changes during a single cut, possibly it indicates little metallurgy based heat manipulation, and possibly to things such as inclusions or other steel inconsistencies. It's only thoughts.

It did make me curious, in regard to the model 70 receivers, if folks ever noticed slight color differences. I'm thinking a finish that has a potential etching component, rust bluing?, may look a little different as to how it shows on the hard vs relatively softer part of the same piece.

My understanding of Kutter's comments was that there was a consistent difference in both feel and effect upon his graver tips on Model 21 actions versus the trigger plates. Yet he said they are supposed to be the same grade of steel. If that is true, then the only explanation for tougher cutting in the action would be different heat treatment. I considered the possibility of inclusions such as scale, which is notorious for eating up cutting tool edges and breaking taps. But he seemed to suggest that he has experienced this difference on more than one gun. And it sounded like he has had similar observations about other Winchester actions and receivers,

Your comment about possible minor differences in bluing shades got my attention, combined with Kutter's thoughts that perhaps the receiver ring of Model 70's has a different localized heat treatment than the areas to the rear. I have a commercial Mauser model 66 S that is pristine except for the fact that the hot blued receiver ring has acquired that purple tone associated with higher nickel alloy steels. Yet the rest of the action remains a deep blue-black. I suppose that I could check to see if the heat treatment of my receiver ring is different than the rear of the action by accepting a couple little dimples from a Rockwell hardness test. But it would probably be a better investment to simply have it hot tank reblued.

I wonder if the floorplate on the M21 is actually the same composition as the receiver. They have known bluing issues on that part.

On mine there is a small area where the blue flaked off. It didn't wear or abrade, it flaked off like a paint would that didn't have good surface preparation.

The receiver itself has no such issues, and I don't carry guns by the metal if at all possible. This is a skeet gun and has never been in the woods.

Now THIS is an interesting post to me.

As is this

I found a 1950 WRAC catalog on-line
https://nhba.yale.edu/assets/uploads/fil...0-Catalogue.pdf

The Model 21 & M12 are of course listed with "Winchester Proof Steel" but there is now no mention of "Chrome Molybdenum"



The Model 37 barrels are listed as “Winchester proof marked”, as are the barrels on the Model 97; which when introduced until at least the 1930s had “rolled steel” barrels. This is likely Winchester Standard Ordnance Steel “cold rolled” Bessemer/Decarbonized steel.



I could not find that the M97 was ever offered with Nickel Steel.

In the same catalog the Model 24 is listed with “high quality steel” barrels.

My Model 50 is stamped Winchester Proof Steel, so they used it on other shotguns than the 12 and 21 circa 1954.

1960 Winchester Western catalog
https://cartridgecollectors.org/content/...l%20Catalog.pdf
"Winchester Proof Steel" is only specified for the M42
No mention of barrel steel for the M21 and M50
M12 with Chrome Molybdenum receiver; no mention of WPS barrel

1965
https://cartridgecollectors.org/content/...l%20Catalog.pdf
No mention of WPS for any of the shotguns; M21, M12, M1200 nor M1400

1970
https://cartridgecollectors.org/content/...l%20Catalog.pdf

1972 catalog listed Chrome Molybdenum for the Y Model 12
https://cartridgecollectors.org/content/...l%20Catalog.pdf

1972 magazine ad listing Winchester Proof Steel barrels and Chrome Molybdenum receivers for the 1200 and 1400
https://books.google.com/books?id=gl31ZxmtlioC&pg=PA13&lpg

I would very much like to send a chunk of M12 WPS from the 50s, and M12 Stainless Steel, for composition analysis. METL only needs about a 2" section.
AND I'm still searching for Hunter Arms Crown and Nitro steel barrels to test.

I think you should consider the possibility that Winchester Proof Steel might simply be a trademark that covers various grades of steel. The WPS steel used for forging an action or receiver may be a different animal than the free machining steel a manufacturer would specify for barrels.