Prim′ing-tube.
（Ordnance.) A tube to contain an inflammable composition, which occupies the vent of a gun whose charge is fired when the composition is ignited. There are several kinds of priming-tubes, fired by port-fire, lock, or friction. The tube is made of quill, paper, or metal, and is charged with mealed powder damped with methylated spirit, or by a detonating composition, such as chlorate of potash and antimony. The tube is slightly smaller than the gun-vent, in the relative proportions of 2/10 and 2/9 of an inch, and a hollow is made down the middle of the composition, so that the fire may involve the whole length instantaneously. The simplest form is that in which the tube is merely a holder for the priming, which is touched off by a port-fire. This is the quill, Dutch, or common metal tube. Another variety has a cross-head or snipe to contain a detonating composition which is exploded by a hammer. This is the cross-headed or detonating tube. A third variety is operated by friction, a roughened bar occupying the hollow in the composition, and exploding by friction the detonating composition in the head of the tube. The rough bar is jerked out by a lanyard. See friction-Primer.
