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/....Zinc alloys have gotten a bad rap thanks to the cheap zinc-based potmetal used by the old Ring of Fire companies of decades passed like Bryco/Jennings, Lorcin, Davis, etc.
I'm merely stating that according to Walther Germany, the PPK/S-22 is not made of ZAMAK, but a proprietary alloy which I surmise is an aluminum alloy due to the weight/size ratio of the PPK/S-22 in direct comparison to the Phoenix Arms CP-22 which is made of ZAMAK and is of equal weight despite being much smaller in size/dimensions.
Could the proprietary alloy of the PPK/S-22 include zinc in its composition? Certainly, but Walther claims that it isn't a zinc alloy and at the very least it would seem to be lighter than most zinc alloys given that fact that they needed to use so much of said alloy in the frame/slide (which I neglected to mention also includes steel inserts in contact areas between the barrel and slide to reduce wear, by the way) to make it weigh 20oz when smaller firearms which are admittedly made of zinc alloy weigh 20oz despite their lesser mass.../
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There are a couple major problems with your theory that the PPK/S .22 LR has an aluminum alloy frame, and a couple good reasons for Umarex Walther to say it isn't Zamak.
1) Your assumption that PPK/S .22 LR must be made from aluminum because it is larger but similar in weight to the Phoenix Arms HP-22 is incorrect.
The according to the Umarex Walther web site, the PPK/S .22 LR is 6.1" x 4.9" by.98" in its largest dimensions, It also has a reported weight of 19 oz on the Walther site. The dimensions are a bit misleading as the width reflects the width at the grip. The slide is only .9" wide while the frame and grip frame are just .7" wide. The height includes the plastic magazine extension and without it, the height reduces to 4.3".
The weight is also misleading as mine weighs 23.6 oz with the magazine and 21.4 oz without. However to be fair mine has wood grips and I suspect the advertised "19 oz" is the weight with the plastic grips and with no magazine - and probably rounded down to get "19 oz".
In comparison, the Phoenix Arms HP-22A is 5.5" x 4.1" (width not specified) and weighs 20 ounces.
On the face of it, it might seem that the frame and slide material of the PPK/S .22 LR must be lighter, even after you take into account the realities of the dimensions and weight. But that's still not the case.
Once you look at how the HP-22A is constructed you quickly realise that the barrel, and sight rib are steel, with the slide and frame cast from Zamak.
More importantly, the barrel in the HP-22A is a pretty hefty piece of steel and is in fact designed with the HP-25A in .25 ACP in mind as well. It is a single piece of steel that comprises the barrel as well as the top of the "slide" and sight rib forward of the breech face.
In contrast, the barrel on the PPK/S .22LR is much less substantial. It consists of a round steel barrel shroud with a small section of breech containing a thin steel barrel liner. There is also a great deal of empty space between the barrel shroud and the slide, which is essential to keep the slide weight low so that it will operate with .22 LR ammo.
In short, there is a lot less steel in the PPK/S .22 LR than there is in the HP-22A.
2) More directly, comparing the 23.6 oz PPK/S (bottom) to the aluminum frame FEG SMC (middle), 18.3 oz with wood grips, and the aluminum frame Beretta Model 70 (top), 16.7 oz with magazine and wood grips, it's obvious the PPK/S is by far the heaviest of these three similar sized pistols.
In short, aluminum is a LOT lighter, on the order of 2.8 grams per cubic centimeter compared to 6.7 to 6.8 grams per cubic centimeter for the standard Zamak alloys, and an aluminum frame would make the PPK/S a LOT lighter than it actually is.
3) Despite popular firearms like the Henry .22 LR lever actions having Zamak receivers (with a steel or brass receiver cover), there is still an incredible amount of hate out there for Zamak alloy firearms, due to the association of any zinc alloy with low purity zinc "pot metal".
With that in mind, why oh why would Umarex Walther claim it's not made from Zamak when Zamak is a known zinc alloy? (Especially given Umarex's association with airsoft guns, etc.)
It's a rhetorical question. Of course Umarex Walther claims it is not Zamak. It would be a marketing disaster if they did. You'll note Henry also doesn't trumpet the use of a Zamak receiver and in fact there's even some disinformation out there stating Henry just uses it for the "receiver cover", which is exactly opposite to how it is used. Henry may or may not have put that out there, but Henry sure isn't correcting it. Similarly, Phoenix Arms refers to the alloy in the HP-22A and HP 25A as "a zinc aluminum alloy", again to avoid some of the Zamak => zinc => pot metal association.
4) Let's talk about what Zamak is and where it gets its name - and why Walther might say, with some shred of honesty that it is not Zamak (while neer saying what it actually is.
Zamak alloys are part of the zinc aluminum alloy family and have historically all shared the common trait of having a constant 4% aluminium composition.
The name "Zamak" is an acronym of the German names for the metals used to create the alloys: Zink (zinc), Aluminium, Magnesium and Kupfer (the German word for copper).
The Zamak alloys are Zamak 3, Zamak 7, Zamak 2, Zamak 5 and Zamak 4. The order will make more sense below as it helps show how they relate to each other.
The base Zamak alloy is Zamak 3 which uses 96% zinc and 4% aluminum (with a tolerance range of 3.5% to 4.3% under the various standards for it (ATSM B240, ATSM B86, etc), with traces of copper (.1% to .25%) and magnesium (.025% to .05%) in it. It offers excellent castability and long term dimensional stability. It's commonly used for die castings.
Zamak 7 is Zamak 3, just with less magnesium (.005% to .02%) which increases the fluidity and ductility for improved performance when casting thin wall components. Some versions of this alloy add a small amount of nickel (.005 to .02%) to reduce inter-granular size, and impurities are more strictly controlled.
Zamak 2 is Zamak 3 with more copper - 2.6 to 2.9%, in order to increase strength by 20%. Zamak 2 is the strongest Zamak alloy and retains both strength and hardness better than the other Zamak alloys, however it becomes more brittle, shrinks, and is less elastic than the other Zamak alloys. It's mostly used in sheet metal forming dies and injection molding dies.
Zamak 5 is Zamak 3 with the addition of less copper - .75% to 1.25%, in order to increase strength by approximately 10%. It also increases hardness and corrosive resistance, but reduces both the ductility of the alloy and the dimensional accuracy in the casting process. Zamak 5 is more common in Europe than it is in the US.
Zamak 4 is used in Asia, where it was developed to reduce the effects of die soldering while still remaining ductile. This was done by reducing the amount of copper in Zamak 5 further to between .3% to .5%.
Here is where it gets interesting however....
There is also Zamak 8, which is often referred to as just "ZA-8". It gets is number not from coming after Zamak 7 but instead from its 8% aluminum content, rather than the more or less 4% common to the other Zamak alloys. Zamak 8 is approximately 90% zinc with 8.2% to 8.8% aluminum, .9% to 1.3% copper and .02% to .03% magnesium.
The increased aluminum content offers the capability of being hot chamber die cast, like Zamak 2, while offering improved strength, hardness and dimensional stability over the other Zamak alloys. Basically, it is similar to Zamak 2, but without the dimensional stability issues. That's important in firearms parts.
Now...I'll give you a partial nod here in terms of weight as Zamak 8, with its 8% aluminum content is lighter, at 6.3 grams per cubic centimeter, but that's still far heavier than aluminum and close enough to the other Zamak alloys that if I handed you a small part made from Zamak 8 and one of the other Zamak alloys you'd be hard pressed to tell the difference by feel.
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So let's summarize.
1) The PPK/S .22LR is far heavier than it would be if it has an aluminum alloy frame or slide. And by "aluminum alloy" I mean an alloy that is made principally of aluminum, rather than principally of zinc.
2) The PPK/S weighs a lot more than other similar sized aluminum alloy frame pistols - roughly 23 oz versus 16-18 oz.
3) Zamak doesn't market well in the firearms industry and no brand that uses it claims to use it for fear of association with zinc and with pot metal.
4) Zamak 8 is a Zamak alloy that departs from the others by using 8% aluminum rather than 4% aluminum. It's enough of distinction that you could say it isn't a "Zamak" alloy without being called an out and out liar. But it's a distinction without a difference as all the Zamak alloys (2,3,4,5,7 and 8) are at least 90% zinc.
Personally, my money is on Zamak 8. However regardless of whether Umarex Walther someday admits is it is a Zamak alloy, or calls it "ZA-8", or claims it is some other proprietary zinc aluminum alloy, it makes no real difference (other than there are established standards and tight controls on impurities for the Zamak 2 through 8). The fact remains it is still a primarily zinc alloy with aluminum being the second metal in it in terms of percentage.
But don't get me wrong. The use of what is no doubt a very "Zamak like" alloy in the frame and slide is an excellent use of the material and from an engineering perspective of being a good choice for the stresses involved, durability, and keeping the costs down in the frame and slide production.
