helixometer

helixometer: An instrument for inspecting the interior of a gun barrel and for measuring the rate of twist of the rifled bore of a firearm. The geometry of a rs a helix. Developed in 1925, in New York by John H. Fisher of the Bureau of Forensic Ballistics.

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helixometer — helix·om·e·ter … English syllables
helixometer — ˌ ̷ ̷ ̷ ̷ˈsäməd.ə(r) noun Etymology: helix + o + meter : a tubular instrument in which an electric light and a prism and lens system enable visual examination of a small arms bore (as in criminal investigation) … Useful english dictionary
Calvin Goddard (ballistics) — Colonel Calvin Hooker Goddard (1891 – 1955) was a forensic scientist, army officer, academic, researcher and a pioneer in forensic ballistics. He was born in Baltimore, Maryland. Goddard graduated with a Bachelor of Arts degree in 1911 from the… … Wikipedia
Comparison microscope — A B Two identical microscopes C C Specimens to compare D Comparison eyepiece (optical bridge) A comparison microscope is a device used to analyze side by side specimens. It consists of two microscopes connected by an optical bridge, which results … Wikipedia

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