Star gauge

(Ordnance) an instrument for measuring the diameter of the bore of a cannon at any point of its length.
(Ordnance) a long rod, with adjustable points projecting radially at its end, for measuring the size of different parts of the bore of a gun.

See also: Gauge, Star

Webster's Revised Unabridged Dictionary, published 1913 by G. & C. Merriam Co.
References in periodicals archive ?
William Brophy, were skeptical of the star gauge's effectiveness.
Cube star gauge implies the three lepton families (to be published).
Another time I was offered a fake M1903 National Match rifle, but it was easily identified as a fake by comparing the bogus Star gauge marking at the muzzle with a real Star gauge marking pictured in one of my reference books.