Richard Atkins considers the pros and cons of steel shot and addresses the principal question: is it a suitable replacement for lead?
The topic of using steel shot in shotgun cartridges has been debated for more than 20 years. In fact, ever since the use of lead shot was banned for use over wetlands, Sites of Special Scientific Interest (SSSIs) and areas where wildfowl are found and hunted. Precise restrictions vary between countries but the essence is that, to reduce the chances of wildfowl ingesting lead shot, the material was banned for such use.
Wildfowlers were left largely to get on with things. With the US having a similar lead ban for wildfowl, much early development came from there. Early steel shot loads drew considerable criticism, with increased levels of wounding/crippling of birds being recorded. This gave steel shot a bad start in shooters’ perceptions and those initial problems still crop up in discussions when the effectiveness of steel is discussed.
Things gradually improved as cartridge makers found ways to improve patterns and performance. Special extra-strong plastic cup wads were developed to ensure pellets would not be pushed through the shot pouch walls by the combination of internal vector forces and abrasion from friction at the pressure points.
New propellant powders were developed and, with improved steel shot pellets and plastic wads, the overall effectiveness of steel shot cartridges improved. Shooters have gradually become more used to using steel shot and its characteristics. These do differ from lead for reasons that are clear when considering the key differences between lead and steel shot.
Density
There are two overriding factors with steel shot that result directly in the main problems associated with replicating lead shot performance with it. These are its lighter weight due to its lower density/specific gravity—relative density—and, importantly, steel’s significantly greater hardness.
These two factors combine to pose several problems that make it very difficult to safely match the ballistic properties of lead shot ammunition. They particularly pose the need for great caution in providing the protection afforded to the bores of guns used with steel shot ammunition to prevent damage to the barrels.
I have been testing conventional lead shot cartridges, commercial and hand-loaded—for both clay and game shooting—for more than 40 years. I have done far less with steel shot cartridges but, as the pressure on shooters of all persuasions to use non-toxic shot wherever possible has increased, I have been closely following progress in that regard.
With the joint announcement from the major shooting organisations in spring last year about the need for a voluntary phasing out of lead for game shooting over a period of five years to 2025, the move to non-lead shot for game use has becomea more urgent issue.
My look at the pros and cons of steel shot in relation to lead shot ammunition in this issue is not a treatise on every aspect, as that would require a modest-sized book and, in any case, there are fast-moving developments with new products being introduced to meet the demand. I do, however, attempt to put a few matters into context and explain the key issues raised so that a clearer view of the positives and negatives emerges.
I also try to shine a light on some issues that may not have been widely understood as yet. These points can be expanded in the future as more developments arise.
Before I start, a warning: the list of pros is going to be much shorter than the cons.
Tackling the key issues
Let us take a closer look at the key issues and how cartridge makers are working to overcome them.
Hardness: Steel shot is very much harder than lead. This becomes clear if you try to crush a steel pellet in the standard device used for assessing the crush value —the standard measure for relative hardness of lead shot pellets. Lead pellets will be crushed typically within the range of 45% for soft shot—as might be found in ‘budget’ clay target cartridges—and 15% in premium cartridges.
Applying the same force to crush steel shot merely marks the faces of the crushing device and gives no measurable percentage crush effect. Steel shot used in shotgun cartridges has limits placed on its hardness by the CIP, the international body responsible for setting the parameters for the manufacture and testing of guns and cartridges in member states.
The CIP limits for steel shot hardness are ≤110 HV1 (≤125 HV1 individual value). The fact that it requires the Vickers pointed diamond indentation method to measure the hardness of steel pellets is a clear indication as to the degree to which steel pellets are harder than even the hardest of high-antimony lead shot.
All modern gun barrels are made of steel—albeit a different grade to steel shot—but the similar hardness and forces generated under cartridge ignition and shot load acceleration creates the generation of forces more than able to score and cause damage to gun bores. For this reason extra strong wads, with shot cups able to prevent contact with the barrel bore 100% of the time, are essential.
Lower density : The lower density of steel shot invokes two important factors. Steel pellets are lighter size for size and therefore larger diameter pellets must be used to attain a similar striking energy. Larger, lighter pellets take up more space; this means steel shot wads must have larger volume to fully contain all the steel pelletsin the load.
Arising from these are more factors for cartridge makers to consider:
Steel pellets typically need to be two sizes larger than lead pellets for a similar striking energy. This adds to volume issues of fitting everything into standard cartridge cases. It also means the frontal area of the pellets is greater. This increases the drag larger pellets encounter travelling through the air and therefore the rate of pellets’ velocity loss in flight. Their rate of deceleration will be greater than smaller lead (or other heavier material). This is why the difference in forward allowance between standard velocity and high-velocity cartridges becomes so small as range increases.
The resistance to shot moving through the air (drag) is not linear; it increases as the square of velocity. Hence increasing velocity to counter lower energy due to lower density/weight brings its own issues – rapidly diminishing velocity gains and considerably increased recoil. Diminishing returns in action.
The CIP has set out velocity and momentum limits for steel shot cartridges. These severely limit the potential for truly high-performance steel shot cartridges (and are a subject for deeper discussion).
What wads?
Wads for steel shot must be very strong. Plastic wads made from HDPE (high-density polyethylene) have thicker walls than lead shot wads and, to allow the same shot load weight as lead in standard-length cartridge cases, they have very small cushioning centre sections between wad cup and gas seal. Some have no such cushioning section at all, with the gas seal part of the shot cup.
HDPE steel shot wads are often made with complete shot cups having no petals, as a majority of lead shot wads are produced as part of the moulding process. Steel shot wad cups can be cut either prior to, or as part of, the cartridge loading process.
Steel wad shot cups are typically slit after moulding. This is to minimise the gap between each petal, because the gap – essential when moulding the petals —is a potential weakness. The steel shot could be forced through the gaps and therefore allow the steel pellets to contact the bore, forcing cones or chokes, which would inevitably cause damage.
Cutting shot cup petals adds a tricky step in the loading process that can slow down production and cause problems when, for example, blades break.
The current purging of conventional plastics from cartridges, primarily for wads that are ejected some distance from the gun and therefore not usually recoverable in a field setting —but with moves to include cartridge cases too—makes for an even more difficult situation.
Cartridge makers have spent years developing cartridges to suit every need and in a wide range of calibres. Now, within a short time frame, they must find a replacement material for two vital components—the lead shot and HDPE plastic wads. Add to this the fact that conventional felt and fibre wads, which have recently been making a strong comeback, especially for game cartridges, cannot be used with steel shot. These wads do not protect the bores from being directly abraded by steel shot, so it becomes clear that cartridge makers really do have a mountain to climb.
Time frame
Small wonder that the joint response from UK cartridge loaders to last year’s phasing out of lead announcement expressed grave concerns about the time frame being suggested, especially in the light of such wholesale changes in the products they are being required to manufacture. It is patently impossible to overcome all the issues, some
of which are highlighted in this article—but by
no means all.
Even when suitable replacements might be found, that does not mean they can be loaded on the same loading machines as those used with lead shot. Production rates will almost certainly be slower, increasing overheads, and increased costs will filter down to the consumer, which could easily reduce demand later.
A wrong choice leading to a false move, such as a wad made from a new and therefore far less known material, could cause damage to bores and lead to damaging claims for already under-pressure cartridge companies. In reality it could mean the difference between staying in business and not.
Clearly some of the topics touched upon here have the potential for longer-term repercussions in various directions. There is much more to discuss in the future.
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