Curt J has it right. First census 1790. Matter of public record. Ancestry.com makes it painless. Here are other things to track down when researching a gunsmith. Church records, court records, prothonotary's records, death records (estate inventories are often useful), orphan's court records, sheriff's records (writs occasionally surface), city registers and advertisers, old newspapers, old letters.
This is a day or two in the court house and a day or two around town for either a professional researcher or a law clerk. Often you hit serendipity...a surprise find when you aren't even looking for it...and this is one of the things that prompts geeks like me to make a lifetime out of investigating history and policy. Concrete listings from such sources, with no subjective editorializing, are considered by me and like minded scholars to be "hard data." And, regarding terminology, we never "prove" anything. We offer supporting evidence/documentation for the hypothesis under consideration.
You either need to learn how to persevere yourself or pay one of us to do it at a couple hundred bucks per diem. When you break it down, we're cheap compared to lawyers and paramours. It does not really take a lot of brains; rather, self discipline, goal focus, and anal-level organizational skills are more useful in such endeavors. Sometimes brains actually get in the way because we start relying on notions instead of facts. Newspapermen call it editorializing; evolutionary psychologists have been known to refer to it as existential bias.
Francis Bacon said it best, "Reason is a whore." What he meant was to go out and examine inductively, then conclude, rather than try to use mental gymnastics to arrive at truth. That's why we are so fussy about facts, terms and their definitions.
