Library Thursday

First off you can see that we changed the title for the Thursday post from book review to library. This was done because I wanted to add more then just book reviews. I wanted to add information to the Gun Lab library that I thought would be useful to you.

So this first post is from a friend of mine that wants to remain anonymous. So for this post we just call him Joe. Joe had the opportunity to have every piece of brass test that he had that was attached to a weapon. This included Maxim guns, Nordenfelt weapons, Gardner guns and any thing else he could find. This is that report. I found it interesting and very useful. I hope you do to.

Bronze Composition Analysis document

2 comments to Library Thursday

  • John D.

    All of the compositions found are a cast ‘red brass’, generally conforming to the grade then known as ‘gunmetal bronze’. Its average composition at the time was 85% copper, 10% tin, 2% lead, and 3% zinc. Over time, abundant zinc replaced some of the more expensive tin until gunmetal bronze had about equal parts of tin and zinc.

    It is worth noting that at the time most of these parts were cast, few foundries had the ability to determine the exact composition of their castings. Most used known scrap with some virgin metals to produce their melts and relied on experience to get their charge formulae correct. This worked fairly well for the unsophisticated alloys of the day.

    Typical foundry practice would involve breaking an attached specimen bar which a highly experienced old hand would then ‘read’. The old hand would assess the color and texture of the fracture surface in sunlight to determine acceptability of the metal grade. Lead was the most difficult to assess, since it tends to segregate by gravity and the lead content of the specimen bar might not correlate well with the actual lead content of the castings. This explains the higher variability of lead than the other elements.

    The elements other than copper, tin, lead, and zinc are residuals picked up from scrap and ore contamination. Sophisticated refining steps to remove these residuals were not implemented until well after World War I, and adoption of extra refining was concentrated on more demanding copper based alloys.

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