The Corbin JMK-1-S Jacket Maker manual explains how to cut, cup, draw and trim precision bullet jackets using the kit and compatible dies.
This manual describes the Corbin JMK-1-S Bullet Jacket Making Kit, which works with the Corbin S‑Press to produce .452‑caliber jackets from 1‑inch wide copper strip. It details the required dies, copper strip preparation, and the sequence of operations—disk cutting, cupping, drawing, and trimming.
Operational steps include using the Disk Cutter Die to cut disks, the cupping die to form short cups, successive draw dies (JRD‑2‑S, JMK‑2‑S) to reduce the cup to the final jacket size, and the ET‑2‑S adjustable trim die to finish the mouth. The kit can be extended to smaller calibers down to .10 with additional draw and trim die pairs.
| Copper strip thickness | .030 inches |
|---|---|
| Initial jacket caliber | .452 |
| Cup diameter after first forming | .600 inches |
| First draw diameter | .500 inches |
| Final jacket wall thickness | .015 inches |
| Final jacket length | 0.75 inches |
| Press ram travel (short stroke) | 2 inches |
| Press mode for cupping | short stroke (swaging) |
| Press mode for drawing | long stroke (reloading) |
Cupping is performed in short‑stroke mode with a 2‑inch ram travel, using the cupping die and spring‑supported guide.
The ET‑2‑S adjustable trim die snips off the rough mouth section, leaving an evenly trimmed jacket of the desired length.