doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Shooting Fox with annealed frame?

Say whO...

As shallow as case harding is I figured it was done more to protect the engraving.

There are plenty of guys [most} who had receiver of Fox, Parker etc recased and all they got are fancy colors. Has anyone ever heard of any modern case hardening shops sending a test strip of similar steel back with the receiver, along with information on case depth - penetration? Modern recasing is like picking the color of your new car without checking if theres an engine under the hood.

Old receivers were (are) made of mild steel (think carbon alloy content below 0.4%). They will not through heat harden under any circumstance. They are easy to case harden and to get case colores on. The case, as mentioned, is very thin and contributes little, if anything useful, to deflection strength. All steel (all metal, for that matter) parts will act as a spring until their yield points are exceeded. Through hardened steel parts make springs that will stand more strain (think deflection) than soft steel. I doubt that the case layer will add anything to a steel part acting like a spring. However, the case will reduce wear on "bearing" parts/surfaces. And, it will add a lot to corrosion resistance (high carbon steel is much more corrosion resistant than is mild steel).

The parts we usually worry about wearing are the hook, hinge pin, barrel lugs/rib extensions, and bolt(s). These are not usually cased. The breach face and action knuckle might benefit from case layer wear resistance. However, both areas are low pressure and low speed bearings during action cycling that are easy to keep well lubed.

I believe it was/is somewhat common for Brit bespoke gun customers to take their new guns shooting before engraving and hardening to be sure they were satisfied while alterations were still relatively easy to make.

DDA

Rocket, you cautioned me some time ago about the possible lack of re-casing of the blued frame on the Ithaca NID I mentioned in an earlier post to this thread. I've worried about that ever since, but I have been shooting ducks using hard kicking Bismuth shells for a couple of years and don't notice any damage.

Here's a picture of the frame. You noticed the gap at the knuckle on this gun. It hasn't gotten any worse as far as I can tell.



Bobby suggested trying a file on the frame to determine hardness. I did that but don't have enough experience filing on guns to tell whether its re-cased or not...Geo

Well, as I try to remember where I got that information, the skin aluminum on a monocoque fuselage is very thin in relation to the cross section of the fuselage but adds tremendous resistance to both torquing and bending of the fuselage. I remember when I read the article that that was the conclusion that I came to. And apparently the low carbon frame doesn't need much stiffening as the Winchester 21 action steel is only about double strength of the low carbon steel but doesn't require case hardening.

I wonder what the difference in hardness is between the 21 steel and unhardened low carbon steel? I bring this up because of the contention that receivers are case hardened primarily to resist wear, say between the knuckle and the iron, which of course should be lubricated and have no wear.

"The case, as mentioned, is very thin and contributes little, if anything useful, to deflection strength."

I do not agree with that statement. It is inconceivable to me that all the pre-WWII makers would have bothered with the difficult and costly case hardening of their doubles if that were true. Especially during the depression years, when cutting overhead was paramount for companies to reduce costs and stay in business.

Shooting an annealed gun more than a few times is just asking for trouble. That being said, just because a gun has had its frame blued does not necessarily mean that it was annealed. It is probably far more likely that the case colors were brushed off and then it was blued. Rusting agents will work just fine on a hardened frame.

If a case hardened receiver is annealed, is it the whole receiver or just the thin hard case that can even be annealed. Didn't case hardening come about because the iron or very low carbon steel that was readily available, could not harden on it's own.

Also could be that if a receiver is permanently bent, it was deflected to a point that was exactly the same regardless of how hard it was. It may be that a classic receiver that was unable to harden, except for the created case, was less likely to crack than a through hardened receiver. Maybe?

OK, lets do a wee bit of metalurgy. Anyone with differing information is most welcome to step right into this. I'm not nterested in being right, rather that we all know the truth.

Steel changes modulus very little due to hardening. Modulus is the amount of strain (movement/deflection) you get for a certain stress (applied force). Hardened steels simply have a higher yield point. Example: if I made two identical springs from "soft" and "hard" steel, they would behave almost identically as springs until the "soft" one was deflected beyond its yield point. The "soft" one would now be permanently bent (dimensions altered) while the hard one would return to original dimensions. Now, same scenario except we case harden the "soft" one. Again, almost identical behaviour until we strain the "soft" one past the core's yield point. At that time, the core is bent and the case is trying to return the core to original dimensions. Calculate the difference in strength between the core and case shell and you will know the amount of influence the case shell can have. Now, think of the action as the spring. Many times over the amount of metal in the core as in the case shell!! Post if you don't follow that logic or disagree.

Shotgun actions were designed and developed (cut and try) using mild steel. It was what was available, more or less easy to work, reasonably priced, and workable sections met weight and strength requirements easily. The metal industry was used to case hardening - SOP. The difference in surface wear and corrosion resistance (think heavy shooting days in damp 'ole UK with black powder and no modern oils or cleaners) between a "soft" steel surface and a case shell surface is remarkable. So, it was relativly a small jump to case harden actions. CCH was a byproduct and not even used intentionaly early on.

Clearly, a "soft" receiver with a case shell is better than a through hardened receiver that is sufficintly brittle to be prone to cracking. Case hardened "soft" receivers were plenty good, so there iwas little push to develop a through hardened receiver. Modern steel alloys and machining techniques have, of course, changed this picture.

DDA

AmarilloMike,

I was once told by the manager of the M21 custom shop (Bruno Pardee)that their specifications for the M21 frame called for Rockwell 42 to 48 but that they tried to keep them about 42 so they could be engraved. Anything over 37 starts to be difficult to engrave which is why most engravers bemoan the hardness of the 21. I have engraved a few for the custom shop in the 80s and early 90s 'till they closed and they took a good bit more time to cut than other guns because of the excessive tool breakage. Ditto for M70 actions.

I do not know what mild steel measures in hardness but would guess in the 20s to maybe the low 30s.

Annealing older shotguns and recasing with no hardness but plenty of pretty colors was very common in the 90's. It avoided warping problems.
The guns suffered no mechanical problems from being in the soft/annealed condition till they were subjected to some real world use.
Sporting Clays and other target type shooters were having problems with galling parts. There was hardness needed in the very least at the knuckle of the frame and it's forend.

Even if no hardness is present,,the gun will perform nicely as a shotgun for the occasional shooter or hunter.
Give it some real use and it'll start showing up,,especially with a tightly fitted unit.
The rants over the Spanish shotguns of the 50's and 60's come much from the same problem. Soft steel improperly or not hardened at all.