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The ubiquitous 12-bore, due to its immense popularity, has become the standard against which other gauges are judged. The “twelve” is regarded as a versatile all-rounder, something of a jack of all trades. Using ultra-light loads, it can be employed in a similar way to a 20-bore. At the other end of the scale in the long 3½in chamberings it is similar to 8-bore loadings. In spite of this apparent versatility, however, there are still enthusiastic goose shooters prepared to shoulder mighty wildfowling pieces and gameshooters who prefer to use smaller guns such as the 20- or even 28-bores when shooting driven game.

Pushing your loads

Problems will arise with any gauge of gun when loads are pushed to the limit. Larger than normal shot loads generate more recoil and long shot strings. A long shot column can produce a large percentage of deformed pellets from contact with the bore (unless plastic cup wads are used), which contributes towards poor shot patterns. Very light loads can also tax the ammunition manufacturer’s ingenuity when it comes to obtaining good patterns, and sometimes it seems there is a bit of instinct involved as well as the ballistic science.

It is, therefore, no coincidence that we have guns of different bore sizes, which evolved originally to use shot loadings appropriate to the gauge in order to produce the best all-round performance. Also, ideally the gauge, shot load and shot size should be matched to the anticipated sport, though there have always been fine Shots successfully using small bores. And now that there are increasing numbers of shooters using very small-gauge guns as a challenge, how do they fare?

Good performance

Performance comes down to good patterns of suitable shot density and pellet energy, or what might be called striking power. Velocity is a component part in the production of pellet energy, but in recent years too much emphasis has been placed on this factor, though it is valued by clay pigeon shooters. There is a considerable difference between breaking a comparatively fragile clay with small shot, where pellet energy is not especially important, and penetrating feathers and muscle of a bird or cleanly bowling over a running rabbit or hare. Excellent patterns at reasonable velocities usually give the best all-round results and it is no coincidence that, as velocities are pushed ever higher, it becomes more difficult to hold patterns together.

A misconception

Small-bore enthusiasts — that is, those who like anything smaller than 16-bore — will sometimes argue that smaller gauge guns throw proportionally tighter patterns and therefore tend to hit harder. This is based on the idea that because the shot column in a smallgauge gun already occupies a smaller area it will not expand as much as that of a larger gun. If this was correct it would mean that a 28-bore would throw a pattern about half the size of a 12-bore. It is a seductive idea, but one that is unfortunately not true.

Testing the theory

To prove this point, I set up a simple test to compare pattern sizes and shot densities. Using a 12-bore as the control standard, it was compared with a 20- and 28-bore and, at the other end of the scale, a light 4-bore muzzle- loader. For the breechloaders shot loads were chosen not only as appropriate for the gauge, but also on the basis of what was readily available at the local gunshop. All loads used No 6 lead shot, as this is the choice of a great many gameshooters.

The distance for testing was 30 yards since this is a reasonable distance from which shots might be taken in the field. For each shot the overall size of the pattern was measured with due allowance for the odd flyer and results took into account that not all shots would necessarily be central on the pattern sheet due to gun fit differences.

Table 1 shows what gun and cartridge makers have known for years — that small-gauge guns do not shoot obviously smaller patterns. What you actually get is a similar spread of shot based on the choke being used, meaning a lesser amount of shot to fill the same piece of sky when compared with a larger gun.

Pellet count

Next we tested for pellet counts (number of pellets in a 30in circle) at 40 yards — the maximum distance at which most gameshooting is undertaken(see Table2). As far as pellet count is concerned, if you prefer small-gauge guns, there is no doubt that you are putting yourself at a disadvantage. It is better to use a smallbore that fits rather than a 12-bore that doesn’t and as a consequence fails to throw the shot where your eyes believe it should be. This is of little consolation, however, when you consider that a 28-bore with 16g load has about half the number of pellets of a 30g 12-bore load to do the same job.

The options, therefore, would seem to be either to increase the shot load, in which case you might as well have a bigger gauge gun for sweeter shooting, or go for more choke to increase the pellet density. The tests indicated that you should not use even a full-choked 20-bore(with the test loads)at distances considered too far for a half-choke 12-bore, especially where full-choke in the latter might be more appropriate. Similarly, a fullchoke 28-bore would struggle to match a cylinder bored 12-bore for shot count. Using more choke brings the shot closer together increasing its effectiveness but reducing the spread of the bulk of the shot charge for any distance and requiring better marksmanship.

Implications in the field

Small-bore guns are delightful and do have their place on the shooting field. But it does mean that you have to be a good Shot, and for anyone having difficulty connecting with a 12-bore, changing to a smaller gun is only likely to make things worse. Also, what is calculated theory and shown on the pattern sheet does not always exactly match what happens in the field, where circumstances are much more uncontrolled. However, it would seem, on the results obtained, that for fairly close driven game such as partridge, the outstandingly good Shot could successfully use anything from 12- to 28-bore, but this does not alter the fact that a bigger gauge will always have the edge in real performance. When faced with super-high pheasants that even begin to tax the performance of a 12-bore, the 20-bore user will be struggling to produce adequate patterns. Then there is always the increased potential for wounded birds. If high-bird shooting is envisaged, then there can be no doubt that the 28-bore should be left in the gun cabinet.

So, for the average shooter, a good big gun will always be a better bet than a good little gun. If you wish to kill things convincingly, use a 4-bore, but the 12- and its close cousin the 16-bore will do most of what you need. The 20-bore is not so far behind for many uses, but those little 28s do need to be used with care. We owe that much to the quarry.

  • Charles Mitford Cust

    I am sorry to appear contrary but the above article is misleading. I have done very extensive long range pattern testing with a wide range of guns in both 12 and 20 bore. To say that 40 yards is the maximum range that game shooting is undertaken is a frankly a ridiculous statement and quite out dated today. Ethically speaking I am not in favour of 60 yard plus high birds but this is the reality nowadays.

    I have seen helium balloons on 55 yard cables tethered on one local shoot just to see how many pheasants flew below them, it was less than 5 per cent. On another shoot locally pheasants were flying over the top cable of electricity pylons and the
    height stamps on their bases (a legal requirement under UK air law) showed
    their height averaged 64 yards before taking into account the extra height of
    the pheasants. In Devon birds are shot well in excess of 60 yards everyday and
    I have measured ranges as high as 75 yards with laser range finders.

    The fact is that a 20 bore half choke delivers an average of 23% of its load into a 30 inch circle at 60 yards (a much more relevant range to pattern guns today) in
    comparison to 16% in a half choke 12 bore. I won’t go into all the choke
    comparisons between the 20 and the 12 but the ballistic facts are that a 20
    bore will deliver a considerably tighter pattern per size of choke than a 12
    bore and at 29% exceeds the 12 bores maximum delivery of 24% with a full choke
    at 60 yards.

    Interestingly after 2 years of exhaustive testing I found a book by Purdey dated 1944 in which to my amazement they had drawn exactly the same conclusions with regard to 60 yard pattern testing as I have done myself even right back then.

    For the sake of clarity I will put this more simply. In contrast to what is implied in the
    article, the scientific reality is that a 20 bore firing a cartridge through a
    full choke will deliver 6 per cent more, not less, pellets in a 30 inch circle
    at 60 yards with a 30 gm or 32 gm or 34 gm cartridge than a 12 bore with a full
    choke firing a 30 gm or 32 gm or 34 gm cartridge. In short, the 20 bore out
    performs the 12 bore at 60 yards, not the other way around. This fact was
    recognised even in the early days of gun making by the likes of Joseph Manton.

    That is why the early gunmakers offered the 12/20 models with 12 bore chambers and 20 bore barrels. It was not, as widely believed, because they were lighter, how could they be? all the weight is in the action anyway? No,as the adverts of the time indicate, it was because in those days 20 cartridges only came in light loads. The 12/20 allowed the user to employ the heavier 12 bore loads but reap the intrinsic benefits of the 20 bore calibre ballistics at long range.

    On a separate point, another interesting discovery that my 60 yard ballistic testing revealed is that load for load, a 12 bore full choke delivers the same number of 4 shot pellets from a 32 gm cartridge as 6 shot from a 32 gm cartridge in the 30 inch circle. So using smaller shot just because there are more pellets to start with
    is a total waste of time because at those 60 yard plus ranges the lighter shot
    has spread beyond useful delivery.

    Meanwhile ballistic gel indicates a 30 per cent deeper penetration at 60 yards and 4 shot delivers a more consistent pattern, Ergo it is pointless to use anything less
    than 4 shot at 60 yard plus ranges which sadly perhaps, is the norm for high
    bird shooting.

    I have a huge amount of data on this subject but the main points are
    that pattern tests at 40 yards bear no comparison to what happens to patterns
    at 60 yards, and perhaps surprising as it may be to some people (but not to
    those of a scientific bent I suspect) a 20 bore will definitely outrange a 12
    bore ultimately and produce a better long range pattern, on a load for load
    basis (i.e both using 30 gm or 32 gm or 34gm cartridges) than a 12 bore. The
    best shots on the big shoots around here have known that ballistic fact for
    years which is why they use them.

  • Charles Mitford Cust

    I am sorry to appear contrary but the above article is misleading. I have done very extensive long range pattern testing with a wide range of guns in both 12 and 20 bore. To say that 40 yards is the maximum range that game shooting is undertaken is a ridiculous statement today and quite outdated. Ethically speaking, personally I am not in favour of the current trend for 60 yard plus high birds but it is the reality nowadays.

    I have seen helium balloons on 55 yard cables tethered on one local shoot just to see how many pheasants flew below them, it was less than 5 per cent.On another shoot locally pheasants were flying over the top cable of electricity pylons and the height stamps on their bases (a legal requirement under UK air law) showed their height averaged 64 yards before taking into account the extra height of the pheasants. In Devon birds are shot well in excess of 60 yards everyday and I have measured ranges as high as 75 yards with laser range finders.

    The fact is that a 20 bore half choke delivers an average of 23% of its load into a 30 inch circle at 60 yards (a much more relevant range to pattern guns today) in comparison to 16% in a half choke 12 bore.I won’t go into all the choke comparisons between the 20 and the 12 but the ballistic facts are that a 20 bore will deliver a considerably tighter pattern per size of choke than a 12 bore and at 29% exceeds the 12 bores maximum delivery of 24% with a full choke at 60 yards. Interestingly after 2 years of exhaustive testing I found a book by Purdey dated 1944 in which to my amazement they had drawn exactly the same conclusions with regard to 60 yard pattern testing as I have done myself even right back then.

    For the sake of clarity I will put this more simply. In contrast to what is implied in the article, the scientific reality is that a 20 bore firing a cartridge through a full choke will deliver 6 per cent more, not less, pellets in a 30 inch circle at 60 yards with a 30 gm or 32 gm or 34 gm cartridge than a 12 bore with a full choke firing a 30 gm or 32 gm or 34 gm cartridge. In short, the 20 bore out performs the 12 bore at 60 yards, not the other way around. This fact was recognised even in the early days of gun making by the likes of Joseph Manton.

    On a separate point,another interesting discovery that my 60 yard ballistic testing revealed is that load for load, a 12 bore full choke delivers the same number of 4 shot pellets from a 32 gm cartridge as 6 shot from a 32 gm cartridge in the 30 inch circle. So using smaller shot just because there are more pellets to start with is a total waste of time because at those 60 yard plus ranges the lighter shot has spread beyond useful delivery. Ballistic gel meanwhile proves a 30 per cent deeper penetration at 60 yards and 4 shot delivers a more consistent pattern, Ergo it is pointless to use anything less than 4 shot at 60 yard plus ranges which sadly perhaps, is the norm for high bird shooting.

    I have a huge amount of data on this subject but the main points are that pattern tests at 40 yards bear no comparison to what happens to patterns at 60 yards, and perhaps surprising as it may be to some people (but not to those of a scientific bent I suspect) a 20 bore will definitely outrange a 12 bore ultimately and produce a better long range pattern, on a load for load basis (i.e both using 30 gm or 32 gm or 34gm cartridges) than a 12 bore. The best shots on the big shoots around here have known that ballistic fact for years which is why they use them.