Reloading: A fresh Start

My inbox shows that we’ve had a steady growth in new readers over recent years. Looking back it has been a while since we took a peek at the absolute basics of hand loading, so for all you new readers and as a revision paper for others, let’s go back to the beginning.

The centre-fire metallic cartridge

A bit wordy but it best describes our subject matter. The reloadable cartridge (NOT bullet!) comprises a brass case, a self-contained primer, propellant and a projectile – the bullet. Our only directly recyclable component is the case. We must begin by rejecting any made from ‘other’ materials such as steel, aluminium or plastic since they do not possess the properties required for safe re-manufacture. Brass is an alloy of tin and copper. The ratios of those two elements can, and do vary from one maker to another affecting the behaviour and the working properties of our case during its life.

The case serves two crucial functions, the first being to act as a housing that correctly positions and largely protects the other components and then to act as a gasket during the firing process. Supported by the chamber it must withstand the massive gas energy pressure generated by the deflagration of the propellant. When functioning correctly it must safely contain this pressure, allowing it to act under the base of the bullet and direct it towards the muzzle. I’m sure we’re all familiar with the diesel car engine; well, the peak pressure inside your cartridge case can be as much as 50 times greater than that in the cylinder head as the diesel/air mix detonates.

The consumable bits

Whilst there are two designs of primer, the Boxer and Berdan, we will concentrate on the former since the largely obsolete Berdan deserves a page or two to itself. The primer is the reloader’s spark plug or ignition system, the rapid response to the firing pin. Designed in 1866 here in the UK by Col Edward Boxer the design features three elements. A stamped soft metal (often brass) cup or case, a layer of explosive such as lead styphnate covered by a protective film and a stamped stirrup or anvil having two, three or four ‘wings’ and looking rather like a Ninja star.

In the body of the cartridge case we have the fuel. For our purposes it will be either a double or single based nitro propellant known as a ‘low explosive’. It is a totally self contained material, requiring no external oxygen or other material in order to work. This property distinguishes it from materials that ‘burn’, such as petrol or paper, since these require a separate oxidiser. Once initiated, our propellant does not explode but rather, consumes itself at a sub-sonic rate, generating the gas pressure necessary to drive the bullet.

This rate of consumption, or deflagration, depends upon a number of variables. The first is its specific chemistry, since the manufacturer can ‘tune’ the performance by the addition of chemical retardants and coatings. The second is the actual shape of the flake, kernel or ball since deflagration only happens on the surface as it becomes exposed. If the flake area reduces during deflagration then so will (proportionally) the rate of gas production – and vice versa. And finally, the actual pressure inside the cartridge; the higher it gets, the faster the given propellant will deflagrate. By way of a demonstration, igniting a spoonful of propellant on a log in the garden would be a truly underwhelming experience. To put it into perspective, a petrol engine would not work in outer space… but, subject to certain considerations, your cartridge would.

The energy delivery system

We often overlook the fact that the bullet is a tool. It is simply the means of delivering energy to the target or subject. We talk about muzzle energy, it being the function of mass and velocity of the bullet as it leaves the end of the barrel. Well, the form of that energy is kinetic, in other words, motion. All bullets will bleed energy during flight, as they are subjected to gravity and air resistance – some better than others. If we’re hunting game or pests then the ideal bullet delivers all of its remaining energy into the target.

Most low performance bullets are made from either pure lead or more likely, lead alloys containing tin and antimony. As performance demands increase we find lead bullets with a coating of copper alloy – copper washed, or with a copper cup crimped to their base – gas checked. For supersonic performance the majority of bullets are constructed from a lead alloy core that is swaged, hot poured or bonded into a cupro metal (gilding metal) jacket. For extreme duties the bullet may be machined from solid copper alloy or brass – solids. Some military bullets employ a steel jacket in place of the copper, alloy although this may be masked by a copper or brass wash finish, or a bright lacquer coating.

Outline planning

So, those are the ingredients required to make our ammo. The reloading process will start with the case. We’ve binned those made from alien materials and must now prepare the brass. This involves restoring it as closely as possible to the original manufacturer’s size or to a best fit in the chamber of our rifle. Boiled down to the basics, we need to remove the old primer and return as much as necessary of the case to a safe working size. We then need to install a new primer, a safe charge of propellant and fit a suitable bullet. To achieve this we will need a set of dies designed for use with our specific calibre. We will also need a machine to hold the dies, a press and a means of locating each case within the press – a shell holder.

Additionally we will need an accurate means of measuring our propellant and a reliable indication of the weight and type that we require; a reloading manual. Next month we’ll get the machinery running!