The cap for small arms is made of copper. It is very slightly conical, with a rim or flange at the open end. It has four slits extending about half the height of the cap.

The cap is charged with the above percussion powder. To protect the powder from moisture, and also to secure it from falling out, it is covered over, in each cap, with a drop of pure shellac varnish.

The copper for making the caps is obtained in sheets, 4 feet long and 14 inches wide, weighing 3 pounds; a variation of 4 ounces, more or less, is allowed. The copper should be pure, free from seams, holes, or blisters, well annealed, and as evenly rolled as possible, with straight and smooth edges.

The copper is cleaned by immersion in a pickle, made of 1 part in measure of sulphuric acid, and 40 parts of water; it is scoured with fine sand and a hand-brush, and washed clean in running water, after which it is well dried in clean sawdust, and rubbed over with a cloth slightly oiled, when it is ready for the machine.

Making And Filling The Caps

Both of these operations arc performed by the same machine. The sheet of copper is adjusted on the table of the machine. The hopper is filled with the percussion powder, and the machine put in motion.

The star or blank is cut by a punch, and transferred to a die where it is formed into a cap by a second punch. The cap is caught in the notches of the revolving horizontal plate, and carried, first under the hopper containing the percussion powder, where it receives its charge of 1/2 a grain, and then under a punch which drives the charge firmly into the cap, and lastly, to the drop hole, where it falls into the receiving drawer.

The hopper is supplied, from time to time, from the 1/2 pound box, while the machine is at rest, using a small copper scoop for the purpose, and the box returned to its special closet, at least one yard from the machine and above its level, before the machine is put in motion.

As a cap is occasionally exploded under the punch in charging, all dust of percussion powder should be frequently removed, and only a small quantity of percussion powder kept in the hopper. The receiving drawer should be emptied after each sheet of copper is completed. 2314 caps are made from each sheet 48 inches long and 14 wide.

The average work of ten hours, including all necessary stoppages, is 31,000 caps for each machine.

Preparation Of The Varnish

Dissolve 1 pound of the best gum shellac in 1 quart of rectified alcohol at 95°. The solution is made most readily at a temperature of about 120°. It must be stirred frequently till all the gum is dissolved. It is made and fit for use in four hours.

The varnish is best made and kept in glass vessels. 1 quart of alcohol and 1 pound of shellac make 1.4G quart of varnish; a small quantity of alcohol is occasionally added to thin the varnish when it is used.

Eighteen quarts of varnish are required for 1,000,000 caps. Two quarts of alcohol are required for thinning the varnish.