by “Point729”
Introduction
So, what is reloading? Essentially all reloading is classified as manufacturing ammunition. It isn’t important how or why stuff is manufactured. It just is. There is no justification for reloading and most people reload either because they have a general passion for shooting or just take pleasure in reloading. For this author, the media – books, videos, websites and fora – surrounding reloading is intoxicating. The introduction of non-toxic shot has certainly spearheaded the drive for better ammunition and caused all of these places to bloom with newly-developed knowledge.
Convenience vs Headache
Factory ammunition is fantastic – lets get that straight right now. Whats not to like? Attractive packaging, often showing the intended quarry, and inside a cartridge which does what the numbers say – your hopes and dreams literally written (or printed) on the box!
Take for example Gamebore’s “Dark Storm” range, which was developed and marketed exceptionally well. I can’t remember another shell for which the reach of the marketing campaign has come close to what Gamebore have achieved.
It’s a good shell too. Gamebore have done all of the hard work of choosing components, putting them together safely, loading them consistently, testing the resulting cartridges, proofing them and packaging them attractively. That’s a lot of investment in a single brand of shell.
Every brand of ammunition also has a marketing budget and the use of that budget is carefully targeted. Advertisements don’t appear randomly in magazines but are deployed strategically for their intended audience: you are much less likely to read about the latest game shell in “clay shooting weekly” for example. Humans are generally susceptible to such marketing: it’s worth remembering this when a shell which promised wonders fails to impress.
Against all of that, the home loader, due to the lack of available resources, must restrict what shells he can safely make. Home loading can cause frustration: the lack of resources, the lack of components and information about them – that’s the headache. Even with a tried, tested and published recipe, some development may have to be done to tune a home load.
Factory ammunition is convenient and saves on space, resources and equipment -but in buying it, you are a slave to the market and its prejudices, cartridge (un)availability and are forced to pay for that “privilege”. The home loader may make more effort for his cartridges, but he more often ends up with exactly what he wants.
Load Development
On one level, load development is nothing more than seleting components to manufacture the best ammunition for any given application. When you buy any factory shell that development has already been done for you – that’s why we pay for factory ammunition. It is safe and for the better part, works very well.
When the home loader makes a shell it is often to a set recipe. This recipe has multiple components: gauge information, hull, powder, wad and shot. Commercially manufactured shells are generally excellent for their intended purpose, often indicated via printed pictures of the intended target(s) on the box or the shell itself. One question always remains, however: what actually makes “great” ammunition great?
Let’s discuss factory shells first. Fact: they are made very cheaply. Cartridge manufacturers exist to make money – it just so happens they make shells too!
Commercial manufacturers are financially savvy. Factory shells are made using powders best suited to that shot payload and often with decent pressures and performance. That’s why shell manufacturers buy certain powders – because they are best suited to the product that shell manufacturer wants to sell. They save thousands of pounds by buying in bulk and using powder only for its intended application which usually results in the smallest quantity of powder required to do the job. Less powder in each shell means more shells manufactured per 25kg drum, which means more profit.
The use by manufacturers of “crossover” components, such as wads that can be used in more than one type of cartridge, is another way of improving margins.
When the home loader manufactures a shell, it is often with a domestic grade powder. These are very different from commercial powders. For example, domestic powders might be labelled as “suitable for 24g loads” or suchlike, in a particular gauge, on the basis of the available loading information, but this is often a slight misrepresentation of their capabilities.
Important: just because a particular powder makes shot leave the barrel doesn’t mean it is any good at propelling that weight of shot. Due to the cartridge pressure limits specified by the C.I.P. (most importantly, PTmax, the absolute pressure limit), a powder may not perform well (or safely) for a given application. Certainly, not all powders are “jacks of all trades”.
When powders are used in an application to which they are not suited, performance can be erratic, particularly at extremes of pressure. So that begs the question: how do we recognize what is good or safe? Moreover, it follows that we should ask: out of all the loading data available, which recipe is best? Results derived from pressure test barrels and chronographs combined tell us when things are working (or not). The goal is first to achieve safety, and then to achieve consistency within the specification, be that consistent pressure or speed.
Anatomy of a Cartridge
There are several component parts of a shotgun cartridge: hull (case), primer, powder, wad, shot and closure. These give rise, in turn to the properties of the cartridge: pressure, velocity and down-range performance. All are important.
The hull or case is the container into which the components are placed, primarily so that ammunition can be conveniently carried. In the muzzle-loading era of shotgunning (which continues to this day- Ed.) the case did not exist: the gun was loaded with powder, wad, primer and any over-shot card using the breech as the containing vessel.
Primers ignite the powder contained in the case. They can vary in strength (i.e. ability to ignite a powder charge) and can produce different results in different applications.
Powder conflagrates (i.e. burns; gives up its stored chemical energy) in confinement (i.e. within the cartridge, within the chamber) quite quickly. The powder is designed to have a consistent enthalphy of combustion (i.e. the amount of energy released by burning, per unit mass of powder) and different powders release different quanitites of energy at different rates. It is the propelling gas in an un-burned form.
The wad is a funny thing really, but it is an inert medium that fills the hull, produces a gas seal and helps, as a piston, to drive the shot down the barrel. The wad will behave differently when according to the powders / components used.
Spherical shot of a given (inert) material and size is used for the projectiles. The availability of different metals in different sizes for this purpose makes the shotgun a very versatile tool, capable of shooting skeet targets one moment, to geese the next, just by changing the shell. That versatility explains why it is so popular with hunters the world over.
[TBC – Closure]
Understanding Loading Data
Reading a published shell recipe is one thing, understanding it is another. A cartridge reloading recipe is nothing more than a published summary of the results of a test run of shells. However, the simplification of averaging the figures down to a single set of values is its downfall: important features of the raw data – deviations and variations – are lost.
Loading data often includes a value for the maximum pressure produced upon firing. The pressure rise is created by the gasses released from burning nitro powder in the contained space of the chamber very quickly. The maximum pressure generated by a cartridge (and the pressure “curve”, which expresses how long and at to what degree greater-than-atmospheric pressure is produced after fiting) can be affected by many components.
The the diameter of the chamber, the degree to which the powder is compressed, the degree to which the wad can be compressed, the style and design of the wad and the length of the cartridge can all influence pressure. More powder, smaller chambers, greater powder compression, stiffer wads and those which obturate (i.e. seal the bore) more effectively and shorter cases will all tend to increase pressure. The respective opposites are true in all cases.
Most significant, however, is the quantity and the conversion efficiency of the powder (i.e. how well and how quickly its solid matter is converted to gas). More powder will produce more gas and raise pressures. Faster conversion or more efficient conversion will also give the possibility of higher pressures; the factors listed above and others besides determine whether this will actually occur.
A Simple Approach
A shooter may have a preference of shooting a certain load weight and a homeloaded cartridge can be loaded with a varied shot sizes. The simplest and most common form of load development then, is to find one safe recipe for primer, powder and wad and to change the size (but not the quantity) of shot. A standard clay cartridge can be safely turned into a game cartridge in this way, by switching the shot size from #9 to #6.
Lead shot costs the same, irrespective of size, to home loaders and commercial manufacturers. Conversely, a comercial shell containing #6 shot is usually sold at a much-inflated price compared to the same cartridge (i.e same recipe) loaded with #7½. In this way, the cartridge manufacturers increase their margins.
Arguably, changing the shot size of a cartridge isn’t even “load development” so much as “loading versatility”, but that does not make it worthless. It achieves a positive change to the external ballistics, according to requirements, without altering the internal ballistics and potentially rendering the cartidge unsafe.
Load Development “Proper”
Load development usually involves designing a shell which is superior for the intended purpose or which gives some other advantage unrelated to performance. This is often achieved using components that are themselves superior to standard “factory” components. A reloader might change a powder to produce more or less speed, more or less pressure or – without aiming for any specific effect – simply, a better cartridge. Financial incentives can also drive load development and many reloaders strive to create a shell that offers better value for money than a commercial equivalent. This is often (but not necessarily) achieved at the cost of performance or consistency.
The mechanics of a shotgun cartridge are quite technical – there is a lot going on when one is fired! The shot column leaving the barrel at high speed is only the end result of a long chain of events and the only part of that chain whose behaviour can be directly observed by the common man. To assess a cartridge properly, specialist equipment is needed: a pressure gauge and a chronograph, used together, will give an overall assessment of a shell’s behaviour.
Pressure is usually measured at a set distance from the breech. In the 12 gauge, the pressure measurement is taken 25-30mm (or 1″) into the chamber. Not entirely coincidentally, this is where the powder sits when shells are chambered and where maximum peak pressures will tend to occur. Measurements taken as the shot column moves down the barrel will reveal much lower pressures, returning to atmospheric (or near-atmospheric) pressure at the muzzle, once the shot column has exited.
When a batch of shells expected to match the intended specification have been loaded, they are fired consecutively in a test barrel to asses their performance. This is primarily done to ensure that the loading is safe, but will also show whether the specification has been fulfilled. The intricacies of cartridge behaviour may not be apparent when fired in sporting arms but the test barrel give a lot of valuable information. Statistical methods are further applied to the raw results to assess the quality / consistency of the tested ammunition. If necessary, this process is repeated, changing the loading to fine tune its performance in respect of the intended specification.