If you’ve ever wondered about the purity of the lead/tin casting alloy you’ve mixed or purchased, there is a relatively simple process to determine the percentages.  But first, using a good reloading scale, you must determine the specific gravity (SG) of the alloy.  I recently received permission from SPG®, Inc. to post, on my website, an article I authored on the subject.   It was published in the Summer 2014 edition (Issue #86) of the Black Powder Cartridge magazine.  Following is the link to the article titled, Measuring & Using Specific Gravities of Lead Alloys: 
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Wayne