makers specially skilled in such work. No mere machinist has the skill to make such dies.

One of rhe properties of brass is that when it is worked or drawn through a die it becomes hard, and several draws in succession would make it very brittle. Therefore, between every draw the cups or tubes are sent to a gas or electric furnace where they are heated red hot to a certain exact temperature to soften or anneal them, and after eadi anneal they are washed and dried before they are sent back to the next press. Figure 116 and Figure 117 shows the

various stages that the cartridge case goes through from the original cup, through the various draws, and the trimming, heading, and necking operations, to the finished case. When the cup is drawn out into a long enough tube the ragged mouth is trimmed off, and then it goes to a series of machines called headers which form and stamp the head of the case and form the primer pocket and the rim. If it is a rimless case another machine like a little lathe cuts the extracting groove. Up to this point the case body is straight with no neck. The case next goes to a press which necks it down gradually in four or five sets of punches and dies with several neck anneals in between, these annealings being localized so as to leave the head of the case hard and the neck rather soft. Finally, after the last necking operation, the neck of the case is usually given a last neck anneal to assure that the neck shall have the exact prain structure which will assure against season cracking as the cartridge gets old.

In all these thirty-odd operations it is necessary that the anneals be very carefully controlled in order that the brass shall have just the right grain structure a5 will insure the required strength, toughness, life and temper. To this end each cartridge plant employs a metallurgist skilled in non-ferrous metals whose duty it is to inspect to insure that each operation and anneal is to the required kind, length, or temperature to give the desired property to each case or complete cartridge.

'Ihe sets of dies, punches, tools, ctc., to form one case or one bullet cost several thousands of dollars, while the sets of presses, headers, trimmers, cutters, bullet machines, loading machines, etc., to make cartridges, cost into the hundreds of thousands of dollars.

Figure 118 shows the various stages in THE MANUFACTURE OF A MODERN JACKETED BULLET. The bullet jacket is drawn from a sheet of gilding metal (copper 90 per cent., zinc 10 per cent.) in much the same manner as the brass case is drawn until it is finally completed, being formed at one end and open at the other. In the meantime the lead core is being formed. A large ingot of lead of the required mixture, usually lead, tin and antimony, is placed in a huge extruding press, from which a long wire of lead is extruded. This wire is then fed into a press in which it is cut off into short lengths, and formed into the required

Was this article helpful?

0 0

Post a comment