The single-shot Martini-Henry breechloader was introduced as the British Army's service rifle in 1871, and served for nearly 20 years until it was replaced by the Lee-Metford magazine rifle. Although the Martini-Henry is highly prized by collectors, ammunition for the weapon hasn't been mass produced for nearly 50 years. Martini-Henry enthusiasts often make their own cartridge casings by trimming and resizing 24 gauge, all-brass shotgun shells. The Martini-Henry fires a "bottleneck" cartridge that measures .577 inches at the case head and .450 inches at the mouth, which makes the .579-inch diameter of the 24 gauge shell a good starting point for do-it-yourself brass cartridges.
Trim the brass shotshell cartridge to length for the Martini-Henry conversion. The cartridge overall length (COL) of a finished .577/.450 caliber cartridge is 2.33 inches. To accommodate case lengthening during the resizing process, shorten the shotshell casing to 2.28 inches with a case trimmer.
Heat the upper third of the casing with a blow torch to anneal the brass, then quench the casing in water. Annealing softens the brass in preparation for heavy tooling. Without proper annealing, the neck of the cartridge will likely split or collapse when it's worked in a full-length resizing die. Heat the brass only until the metal acquires a slight blue coloration.
Mount the full-length resizing die on your reloading press. Coat the cartridge with a thin film of case lube, then insert it into the shell holder on the reloading press ram.
Push down on the reloading press operating handle to raise the reloading ram. Run the casing into the resizing die until you meet firm resistance, which you should feel after about two-thirds of the cartridge has entered the die. Raise the ram a further 1/4 inch, then lower the ram and remove the cartridge from the shell holder.
Heat the upper third of the casing with a blow torch, then quench it in water to anneal the brass again. Dry the cartridge and coat it with case lube.
Insert the cartridge into the shell holder, then run it into the resizing die until you meet firm resistance. Raise the ram another 1/4 inch, then lower the ram and remove the cartridge from the shell holder.
Repeat Steps 5 and 6 until you've resized the full length of the cartridge.
Measure the length of the finished cartridge casing with precision calipers. Trim excess brass from the mouth of any casing that exceeds an overall length of 2.33 inches. Lightly bevel the inside of the case mouth with a chamfer tool.
- Always wear eye protection when working with reloading tools.
- Discard any brass you accidentally overheat during the annealing process. Brass heated until it is red-hot becomes too brittle to safely tool or shoot.
- Annealing the brass after each sizing pass is critical. The resizing process work hardens the metal; skipping the annealing step or resizing more than 1/4 inch of the casing at a time will result in ruined brass.