Pewter Quackenbush pop-out pistol

Pewter Quackenbush pop-out pistol 

With thanks to Wes.

There was an interesting discussion of this pewter pistol on the American Vintage Airguns forum.

John Griffiths, author of the Encyclopedia of Spring Air Pistols, said:

It would be very interesting to find out the composition of the metal used,  as this could help date approximately when it was (or wasn't) made.   I believe that zinc-aluminum alloy casting  did not come in until about 1914 and aluminum casting about the 1880's. Lead-tin alloys (pewter) had been around a long time by the 1870's.  

(You can get a fair idea of the composition by measuring the density of the metal. This easy to do non-destructively by suspending the pistol carcase in a beaker of water by a thread and weighing the beaker, and by weighing the carcase on its own.)     

Wes replied:

I weighed the two pistols.   The alloy pistol is missing the breech plug so I measured the black original with the plug out.

The black original weighs.    1 pound, 1.3 oz.

The alloy pistol weighs       14.1.  oz.

Weighed on a digital scale.

John said:

You will also need the increase in weight of a container of water when the carcase is suspended by a length of string in the water. (In other words first weigh the container with just water in it, and then when the pistol carcase is suspended in  it, and then measure the increase in weight)  While you do this the carcase must be totally submerged and it must not touch the bottom of the container.   It is then simple maths (or as you say, math) to calculate the  density of the metal from the water weight and the normal weight.

This was the classic method of working out much gold there was in  sample of quartz ore in the field.

The theory is that the when you weigh it submerged in water, the water pushes upwards on the carcase by a force equal to the weight of water displaced. This force is detected by the scales as an increase in weight.  As the density of water is 1 gm/cm3, this increase in weight is also equal to the volume of water (in cm3)  displaced by the carcase, which is the volume of the carcase.  So you now have the accurate volume of all the alloy in the carcase (assuming there are no voids).  Call this A.  If the weight of the carcase on its own is B, then the  density of the alloy will be B/A.    
Aluminum has a density of  2.6,  tin  7.26, lead 11.3,  zinc  7.14. So you should be able to differentiate between alloys with high aluminum content, zinc alloys, and lead-tin alloys.   

Wes replied:

OK. I did the experiment now tell us what the results mean.
The only parts left in the frame is the brass trigger and brass sear.

container with water.    4lb  15.5 oz
container with water and pistol frame.  5lb  1.2 oz
pistol frame.    15.7 oz

John said:

OK Wes:  Converting everything to grams,  the volume of your frame comes out to be 48 cm3.  The weight of the frame is 445 grams.  So the density is  445/48   =   9.3 g/cm3.

That rules out aluminum  and aluminum-zinc alloys, and according to Google pewter alloys (tin-lead) fall in the range 8.5-9.5 g/cm3.  So it looks most likely that your alloy is pewter, which was in common use in the 1870's. This means that  the pistol could be more or less  contemporary with the cast iron original.  I can't see anyone using pewter to make a pistol after 1914, as the zinc alloys were then available and would be much preferred,
Pewter is softer than zinc alloy, so does your pistol seem that way to you?

Wes replied:

Sounds like pewter to me.   When I had it apart I scratched the frame under the leather abutment washer and it was very soft.  From now on it is a pewter Quackenbush air pistol.    We still do not know if it was made by Quackenbush or not.   I sure would like to know if there are any others out there.   Thanks for the help!! 

Bill Lawrence, a metals expert, added:

Pewter is mostly tin alloyed with other metals like copper, lead, antimony, silver, or bismuth.  It melts at a relatively low temperature , casts nicely, can be easily worked with files and edged tools, even emery paper, and is normally considered a "soft" metal, especially when lead is the major alloy.  And Wes notes that his pistol's body is "very soft".   Which raises the question:  Could a pewter-bodied "gat"-type air pistol have a very long working life?  My answer is: only if the major alloy is antimony and the amount of alloyed lead is minimal or omitted would the resultant pewter possibly be hard and strong enough for such an application.