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Corbin JMK-1-H Bullet Jacket Making Kit
The Corbin JMK-1-H Jacket Making Kit, for use with the Corbin CSP-2, CHP-1, or CSP-2H presses, makes precision bullet jackets in any caliber, some of which can then be redrawn to other calibers and trimmed to length by adding a JRD-2-H commercial grade jacket draw die and an adjustable trim die (ET-2-H) for each smaller caliber desired. The die set typically uses 1-inch wide by .030-thick copper strip, deep drawing grade with finished edges, but can use standard widths of 1.25 or 1.5 inches, in thicknesses of .030 to .125 inches. Corbin furnishes 1 x .030 copper in 5-lb bundles or 50-pound copper coils, and other sizes in 50-lb or 100-lb coil.
The strip is first passed through a slot in the Disk Cutter Die, where a punch mounted in the standard floating punch holder, in the press head, cuts a disk from the inch-wide strip and drops the disk out an angled exit port in the lower die section. The die itself screws into the press ram. The Mega Mite press is used in the short stroke or swaging mode for maximum power. Hydraulic presses can be set up for a short stroke cycle.
The strip is pulled through the slot, while the press ram is moved in short strokes, just enough
to cut the metal. Then the strip is advanced to the next position by observing the relation of the last hole in the strip compared to the edge of the die, leaving enough metal between holes for a good disk to be cut on the next stroke.
After the disks are cut, the cupping die and punch assembly are put into the press. The cupping die itself goes into the ram from the bottom side, which is the opposite of most dies. The spring-supported guide and punch screw into the ram. A lubricated disk is placed in the top of the guide, which in turn is held in position on top of the punch.
The press is operated, raising the ram and clamping the edge of the disk under spring pressure as the guide engages the die. The punch then pushes the disk into a cup shape as it goes upward, into the die. The cup then emerges from the top of the die, and the cycle is repeated. The die forms a short, thick-walled cup.
The cup is then lubricated and placed over the first draw punch, which screws directly into the ram. The draw die screws into the top of the press, and the CSP-2 press is set for the long stroke or reloading mode. The large diameter cups are drawn to the next smaller diameter, while the walls are made thinner and the length increases.
The special jacket drawing dies used with the JMK-1-H are not the usual JRD-1-H reducers, which are used for certain less stringent applications. They are a commercial grade JMK-2-H which uses special heat treated alloy steels, a longer punch, and a nesting-style die configuration for more precise jacket wall concentricity. The punches screw into an adapter, which is used for all of the draw dies in the set (and can also be used for additional new draw dies). The threads on the punches are 5/8-24, and the adapter allows them to fit the 1-12 threaded ram.
After reducing, the cup is then drawn through the second draw die. The jacket wall will be Additional draws can be required depending on the specific caliber, wall thickness, and length desired. Each set is designed specifically for your application. If you specify all the calibers you eventually want to draw, and the wall thickness, taper, or other special needs, then it may be possible to design the original die set to better provide for the kind of draws you will need to make later.
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