Another one for the engineers!!! ......Luger mag shells!

[G.T.]

It's no secert that Luger folded sheet meatal mags are soft,...although, once and awhile you run across one that seems to have a little more spring, and a few less dents..... By and large, they are soft.... The extruded mags seem to be stronger, in both design & materials, by a considerable amount!! I would have to asume that all original Luger mags were made with a very low carbon, soft cold rolled steel....not so sure about the Mauser blued sheet metal ones?, they seem a little better.....but, they all pale when compared to modern pistol mags....which seem to be indestructable, even under the worse conditions possible!!! I read alot about 4130 & 4140 alloy steels...do you think this is what is used into todays mags?? Stainless doesn't figure in the equasion, as I am already aware of their properties.....I'm just wondering about suitable carbon alloy steels! Thanks to all, till....later....G.T.

[John Sabato]

of everday CRS or cold rolled steel and after forming the lips and flanges are probably heat treated to give them more durability. With today's manufacturing methods, I think that the spot weld process gives them superior rigidity over the old folded type magazines like for early lugers. I


don't think there is a sufficient demand for a particular alloy to be mixed just to make magazines. The only stainless type I am personally familiar with is 316, which I used to manufacture literally thousands of outdoor metal enclosures for electronics like traffic signals. It is plenty hard, dulls tools quickly, and is fierce to bend compared to CRS too, but anything made out of it will be lasting long enough for several generations to enjoy it.


Let's also not forget that the very best magazines for the M16 and AR15 class of rifles is made of aluminum! Magazines for combat use are designed to be throw-aways and that includes pistols. We as a group just happen to try and preserve them for historical and collector purposes...


Well that's the end of that combination brain-dump/op-ed.


regards,


John Sabato

[AGE]

G.T. Here are a few answers from a mechanical engineer (not a metalurgical engineer and never worked in the firearms industry). Both 4130 and 4140 are Chromium-Moly steels, 4130 has about .30 percent carbon and 4140 has about .40 percent carbon. They can be quite strong (5-10 times) but much less ductile than low carbon steels. Welding destroys the heat treated properties, and they are probably not ductile enough to form or bend into a magazine shape. The 300 stainless steels are very ductile, but not as strong as alloy steels. My guess is that low alloy steels or 300 stainless steels are used in today's magazines.


AGE

Most likely a more common and lower cost "St Stl" on the order of the 18 - x series, perhaps the common 18-8 St Stl.

It would still be subject to deformation more than Cold Finished Steel, which derives its strength from Molecular Deformation in the Rolling process.

ViggoG

[G.T.]

Hi Guys! so you think a low carbon steel was used with some kind of secondary tempering process? I have checked some of the coll rolled sheet steel in the correct thickness, and it is butter soft, It would form great, but would not last too long with even mild use! Are most alloy steels difficult to form? Thanks for the feedback guys! This is quite a learning experience for me! till....later....G.T.

[wfw]

To oversimplify considerably, a particular piece of steel's mechanical properties are determined by its heat treatment. The reason is that steel forms different crystalline structures at different temperatures, and those crystalline structures have wildly varying physical properties. The heat soak (letting a part sit for a while at elevated temperature) allows the crystals to set in whatever arrangement is characteristic for that steel at that temperature, and the quench (rapid cooling) freezes or traps the crystals in that arrangement. A subsequent temper (a relatively mild reheat) then allows a partial stabilization of the crystal structure to some other configuration, with further modification of the steel's physical properties. The phase diagrams for iron show crystalline phase (austenite, ferrite, pearlite, martinsite, etc) as functions of temperature vs. percentage of various alloying elements.


There are other hardening mechanisms. Precipitation hardening is not based so much on crystal structure, but depends on distributions of elements which precipitate out of the alloy into microscopic clumps. This happens because, for example, carbon is not soluble in certain crystalline phases of iron. The layman finds the concept of non-solubility to be peculiar when applied to solids, but it's true nonetheless. Precipitation hardening is the only heat-treatment hardening available with most aluminum alloys, but its commercial use in steel is relatively rare. The AISI series 15 and 17 wrought stainless steels are precipitation hardened, and I think that's about it.


Another crafty and very old trick is case hardening, in which the carbon content of the steel part is increased locally. That higher-carbon region then reacts differently to the subsequent heat-treatment process than the lower-carbon regions of the part. Typically the part is immersed in graphite and subjected to a heat soak. At elevated temperature the carbon in the graphite is soluble in the steel and is therefore absorbed into its surface. From there it can diffuse into the steel to some considerable depth (in practice, only a few thousandths of an inch). Then when quenched, the high-carbon regions are much harder than the rest of the part. Hence, the hard "case" around the part. This is good for, say, carpenter's hammers. The face can be case-hardened so it isn't diggered up by nail heads. If through-hardened, the hammer head would shatter under impact. The combination of hard face and more ductile body is far more durable (in this particular application, anyway) than any other obvious combination. Case-hardening was the process used in a grander scale to make the armor (Harvey process and Krupp process) in dreadnoughts. The soak times for carbon diffusion could run for weeks, to get a good thick hard surface to the armor plate. So much for those who think "case hardening" is just for the fancy colors.


Another hardening mechanism is work hardening. This can occur naturally as a part is used, or it can be done deliberately. Some common alloys of, say, copper, can only be hardened by this process. A simple example of work hardening in steel is a bend in a paper clip. As the wire is bent back and forth in the same place repeatedly, it begins to harden, to the point that it eventually becomes (locally) brittle, and fractures. In a real engineering "strength of materials" class, this would be illustrated with a suitable stress-strain diagram. Cold-rolled metals are sometimes work hardened; drawn wire usually is. Some metals, such as molybdenum, when cold-rolled, are work-hardened to an extreme degree. Even thin sheets tend to delaminate into two layers, as the outer rolled surfaces are much harder than the interior of the sheet. Work hardening in any metal can be made to disappear by annealing, which is just another heat soak which allows the crystals, all broken up by the working processes, to reform.


In engineering, all of this is very old-hat. Generally, "modern processes" make metal processing cheaper, not technically "better" (as in, more suitable for a particular application).


Now for specifics. Medium-alloy steels like 4130 and 4140 are used in tremendous quantities in applications like, say, aircraft engine mounts. Ultimate tensile strengths are a bit better than those of low-alloy steels of similar carbon content (1030 or 1040), and fatigue resistance is better (hence the aircraft application). Airplanes constructed of tube and fabric (there are still some being made like that) use 4130 tubing more often than not. It welds easily, and the heat treatment doesn't require exotic equipment. Wrought 4100 series stock is commonly available as tubing and cold-rolled bar, sheet, and plate. Cold-rolled was more popular than hot-rolled in the past, as the surface finish was much better (the hot-rolled stuff was all scaly), but nowadays hot-rolled is supplied with a pickled surface (picking is a corrosive bath which eats off the scale).


The strength requirements for magazines are not very stringent. (I would call the inside of a jet engine a stringent environment). Any decent spring steel (say, AISI 1080 - iron with 0.80 percent carbon added) should be just about indestructible. Depending on the part and how one wants to fabricate it, it can be made of annealed material and then hardened, or it can be made directly of hardened material. If one was limited to a garage-type workshop, fabrication (cutting, bending, welding) followed by hardening would probably be suitable. More complex parts (that is, almost anything else besides magazines) would tend to call for more complex processes, and more expensive materials (such as air-hardening alloys, which avoid the dimensional distortions commonly induced when quenching - not so good for precision parts).

There is a grade of Carbon Steel Alloy Known as "Swedish Blue Steel".

Frequently used for leaf springs,such as the sear spring at the aft end of the Luger sear.It can be tempered,(drawn down) to a softer more ductile state and formed into the shapes necessary for magazines.

This would probably have been supplied from the rolling mill in the proper temper in large quanity orders as would be required for a magazine forming production line.

If someone were sufficiently interested an analysis could probably be performed,on an old worthless magazine, by any of a number of quanatative analysis labratories, for a "Sum of Cash". How much? I have not the faintest idea.

ViggoG

[G.T.]

Thanks a bunch for all the info. you are light years ahead of me!! I have had a litle experience with 1075 & 1095 (just enough with 1095 to let me know I should have been using 1075!!) and I see the potential with these steels......a note to all! This gentleman is on top of his game....I think he has both the tech. knowledge and the applied knowledge...He is definitly dangerious when allowed to run loose in the fabrication field! Again, thanks wfw, for the info, it is greatly appreciated, till....later...G.T.

[Big Norm]

[G.T.]