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shot. These three shot types can be produced in different
cartridge lengths for a given gauge. Thus 12 gauge cartridges
can be made in 2.5”, 2.75”, and 3.0” lengths, depending upon
the species of game being hunted. The production of 2.5”
cartridges in 12 gauge allows older, British-made, guns
chambered and proofed for 2.5” cartridges to continue to be
used for hunting with these types of lead-free ammunition.
Twenty gauge cartridges can also be made in 3.0” lengths.
Tungsten-Matrix and bismuth-tin alloy shot can be loaded
into cartridges using the same components (primers, powders,
shot cups and wads) used for making lead shot cartridges.
All four shot types can be loaded into cartridges with photo/
biodegradable shot cups designed for use in locations where
plastic shot cups are not permitted. Tungsten-based Hevi-Shot
is produced for use in hunting both upland and wetland game,
and the USA manufacturer makes cartridges loaded with this
shot in a variety of gauges, though only 12 gauge cartridges
appear to be offered for sale in the UK.
Steel shot has a density of 7.8 g/ml, less than that of lead shot
(lead-antimony shot is approximately 11.0 g/ml). Hunters are
advised to compensate for the lower density by using steel
shot of two sizes larger than the traditional lead shot ( i.e. #4
steel rather than #6 lead) to retain down-range energy. The
effective range of steel shot cartridges is still about 40 yards,
quite comparable to lead shot cartridges, when the criteria of
shot pattern density and energy for penetrance are considered
together (Garwod 1994, Pierce et al. 2014). Tungsten Matrix
shot has a density of 10.8 g/ml, very close to that of most lead
shot products, and it can be used interchangeably with lead
shot cartridges, with respect to shooting distances, response
to barrel choke, and ballistic efficiency. Bismuth-tin alloy shot
has a maximum density of 9.2 g/ml, and it can also be used
interchangeably with lead shot cartridges. Hunters are advised
to use a shot one size larger than the lead shot equivalent to
compensate for the lower density. Hevi-Shot is listed as having
a density of 14 g/ml. Thus shooters could consider using shot
one or two sizes smaller that the lead shot equivalent to realise
similar shot pattern densities.
Concerns have arisen about the negative impacts of steel shot
on shotgun barrels and need to be addressed in this paper.
Barrels comprise three regions: the chamber, the barrel bore,
and the terminal choke. Steel shot is much harder than lead
shot and does not deform during the initial detonation in the
cartridge chamber, unlike soft lead pellets. There is no damage
to the chamber because the pellets are still inside the cartridge
case. As steel pellets travel down the barrel, they are contained
inside a protective cup that prevents the pellets contacting the
walls of the barrel and causing damage. The only point along the
barrel where some risk might arise is when the steel shot pass
through the choke. The chokes of different makes of shotguns
are not made in a consistent, uniform manner. Concerns
pertain to abruptly-developed, as opposed to progressively-
developed, chokes in barrels. It is possible that large steel shot
(larger than #4 steel) passing through an abruptly developed,
tightly-choked (full and extra-full), barrel could cause a small
ring bulge to appear, simply because the steel shot do not
deform when passing through the constriction. This does not
occur if the barrels are more openly choked, such as “modified”
or “improved cylinder”11. This is the essence of the concerns. For
shooters with interchangeable, removable, chokes, the solution
is to use a more open choke when shooting such steel shot, as
when shooting waterfowl or“high”pheasants. For shooters with
gun barrels having “fixed” chokes, the choke, if necessary, can
be relieved readily by a gunsmith to a more open choke. The
shooting of steel shot of diameter smaller than #4 does not cause
concerns when fired through tight chokes. The same caveat
about shooting large steel shot through fixed choke barrels also
applies to large Hevi-Shot pellets, which are also much harder
than lead shot.
It is interesting to note that lead shot is hardened deliberately
by the addition of up to 6% antimony, and also by coating
with nickel plate, to resist deformation during detonation and
passage through tight chokes. This is to improve the proportion
of pellets that arrive around the target, especially at ranges of
30-40 m. Steel shot is known to pattern well for this reason, and
without the need of much barrel choking.
LEAD-FREE RIFLE AMMUNITION
This type of ammunition was made initially in the USA in
order to produce bullets with superior ballistic properties and
lethality than many lead-core counterparts, rather than to
produce non-toxic ammunition (Thomas 2013). The leading
US maker, Barnes Bullets Inc., sells lead-free ammunition
under its own name, and sells lead-free bullets loaded into
cartridges made and sold by Federal and other companies.
These are available in the UK (Knott et al. 2009). All species
of UK mammals can be hunted with lead-free centre-fire
ammunition (Table 1). An array of lead-free rifle ammunition
is made by European companies for those calibres commonly
used in UK rifles, as listed in Table 1. Thomas (2013) provided a
11 See the RWS website on this point.
Availability and use of non-toxic ammunition: practicalities and regulations