9mm (No. 3) Bore

The “Number 3 Garden Gun” has fallen out of favour in the UK and finds increasingly little use abroad. Once a relatively-commonly encountered tool for the control of small pests in gardens and orchards (hence the name), it has been displaced by the air rifle and the .410 shotgun for these purposes. Only a handful of manufacturers (e.g. Falco, Fausti) still produce shotguns with a 9mm bore – usually to special order. Although there are still many examples of guns in this bore size in existence, most are old, or very basic construction and spend their lives languishing in the back of gun cabinets, remaining unused except in the most unusual of circumstances.




The first rimfire metallic cartridge was invented by Louis-Nicolas Flobert invented in 1845. He modified a percussion cap, inserting a bullet with the aim of improving the safety of indoor shooting. These cartridges were first produced in 6mm and 9mm calibers, using either a round ball (the “BB” cap) or a conical bullet (the “CB” cap) and quickly revolutionized cartridge design. Later, in place of the bullet, a thick cylinder of paper, packed with shot was inserted into the cap, creating the shot cartridge which still bears his name: the 9mm Flobert.

Varnished, paper-cased 9mm shot cartridges were produced until relatively recently – perhaps as late as the 1960s by manufacturers such as Gevelot. These tended to be both expensive and unreliable: the paper case would often detach from the brass cap and disappear down the bore after the shot, leaving only the brass cap in the breech! Quite what sort of pattern such cartridges would have thrown remains a mystery to us here at SmallBoreShotguns, but a single, 8-10mm hole in the paper would not be unexpected.

More common in the 20th and 21st centuries has been the brass-cased design with its slightly odd bottle-neck shape, sealed with an over-shot card. Such cartridges are still produced commercially by Fiocchi and RWS, containing approximately ¼oz (6-7½g) of shot in (continental) sizes ranging from #12 to #6. According to the CIP, the cartridges should be 1.439″ long, with case diameters of .342″ at the base and .326″ at the neck. Maximum permitted pressure is 13500 pounds per square inch.

It is traditional, when writing about shot cartridges with metric designations, to label them also with the older Imperial gauge equivalent. For example, the .410 shotgun is often designated the 67½-gauge. In the case of the 9mm Flobert, however, confusion seems to reign: the traditionally-accepted designation of “105-gauge” would be correct if the bore size were indeed 9mm, but the CIP specification actually lists a barrel diameter of 8.38mm (.330″) which is approximately 130-gauge.

Besides shot cartridges, two other 9mm rimfire cartridges usable in a 9mm shotgun remain commercially-available: the BB and CB caps. These are necessarily low-pressure cartridges whose designs have remained essentially unchanged since Flobert conceived of them in the 1840s.

The “BB” cap cartridge comprises a 58-grain lead ball of slightly larger than .330″ diameter which is often propelled by the force of the detonation of the primer alone. A tiny charge of ultra-fine smokeless powder is sometimes added to provide extra velocity. The accuracy of this round tends to be poor, particularly from smooth bore barrels and 2-4″ groups at 20 yards should be expected. We can’t find a figure for muzzle velocity for these rounds, but on the basis that the relationship between the equivalent loadings in .22 and 6mm rimfire calibers gives the BB cap approximately 93% of the muzzle velocity of the CB cap for projectiles of identical weight, we suspect that the BB cap probably produces around 690fps at the muzzle. This would mean that the ball projectile possesses approximately 60ftlbs energy at the muzzle.

The “CB” cap cartridge is similar in construction to the “BB” cap except that the ball is replaced by a conical lead bullet. Like the ball round, they may or may not include a powder charge. Accuracy from the conical bullets is usually slightly better than the ball cap but remains poor from smooth bore barrels. 1-2″ groups at 20 yards would be considered good accuracy from this cartridge. Muzzle velocity tends to be in the region of 745fps and energy approximately 75ftlbs. RWS still produce this loading (known as “spitzkugeln” – lit. “conical ball”, after “ball” ammunition as a name for a cartridge containing a single projectile) and the BB loading (“rundkugeln” – “round ball”) commercially.


Pietro Fiocchi always maintained that the smallest shotgun suitable for hunting was the .410, but we may interpret that to mean “for general purpose hunting” since the use of the 9mm shot shell has always included the killing of small game and pest species. Although the rich man may have used Flobert’s bulleted cartridges to shoot at targets indoors as we have mentioned above, it was not long before his invention was put to a rather more mundane but important use: the protection of crops and food stores, particularly from small birds and rodents.

Ballistics & The Situation in the UK

It is impossible to determine value and purpose of the Flobert shot cartridge(s) without also investigating the utility of very small (i.e. #9 and smaller) shot. It is simply not possible to use the 9mm shell for the forms of game shooting traditional in the UK, since the general requirement for these is a cartridge loaded with #7-#4 shot. The number of pellets of those sizes one can fit into the tiny case renders the cartridge almost immediately inhumane: beyond 10-15 yards, they produce no pattern to speak of and therefore give no guarantee that any quarry hit will be killed cleanly.

Even if experience could show a greater capability than the theory suggests (we do not encourage anyone to use a 9mm shotgun on living targets – Ed.), 9mm cartridges containing such shot sizes still represent loadings severely unbalanced in favour of individual pellet energy over pattern and they should be employed only with extreme caution.

A computer-generated predicted pattern image suggesting the performance of 7g/#5 shot through a cylinder choke at a distance of 30 yards.

The 9mm cartridge is probably most balanced with the use of #9 or #8 shot but this may not be saying much. (In fact, it may be the case that the most satisfactory performance on game is achieved by the intentional use of unbalanced cartridges in this bore size – see here for discussion.) Cartridges with these sizes will contain approximately 143 and 111 pellets respectively. With a 20″ pattern circle (implying “aimed” shooting), these cartridges will produce usable pattern densities well beyond 20 yards, though, because garden guns tend not to be choked, they may not manage “all reasonable ranges” – i.e. 40 yards. Smaller shot sizes than #9 will rarely suffer from insufficient pattern density, even using a 30″ circle or cylinder-choked gun.

However: because of the very low muzzle velocity – around 600fps is common – cartridges containing very small shot may be no more humane than those containing the traditional-for-game sizes. The Eley Shooter’s Diary used to specify a minimum requirement of 0.5ftlbs pellet energy for the smallest of game; the retained energy of a #8 pellet fired at 600fps from a garden gun falls below this threshold somewhere between 10-15 yards from the muzzle. Whichever way you look at it, it is extremely difficult to get a 9mm Flobert cartridge to perform adequately beyond 15-20 yards on even the smallest of the commonly-encountered UK quarry species.

Further Afield

The situation abroad is (or has been) different. The Italians, for example, have a long history of shooting songbirds and other migratory birds, many of which are exceedingly small. This, in turn, requires the use of very small shot. Local crops, such as olives, tomatoes and other soft fruit, also suffer at the hands of small pest bird species (e.g. thrushes, finches and sparrows) in the same way than British arable crops suffer at the beaks of wood pigeons and crows. These birds are therefore controlled by shooting (although the shooting of finches and sparrows is now illegal in Italy). Furthermore, some North Italian “delicacies” require the use of (song)birds which the British palette would no doubt find extremely strange – e.g. Polenta e Osei, often made with larks.

Although it is possible to buy 12-gauge cartridges containing shot sizes appropriate for very small birds (thrushes might be killed with #12-#8; sparrows, when they were shot, were generally taken with sizes as small as #14!), the usual practice is to employ a smaller-gauge gun. Apart from anything else, this is for reasons of cost: no bird, however small, requires a shot cloud containing over 1000 pellets (i.e. 28g / #11) and with lead as expensive as it is today, the extra shot, coupled with a high volume of shooting, comes at significant cost for little to no gain.

A computer-generated predicted pattern image suggesting the performance of 14g/#12 shot through a modified choke at a distance of 30 yards.

A half-ounce of #12 shot, for example, contains over 600 individual pellets. Such a cartridge provides both incredible pattern density and sufficient energy for these purposes: a tiny fraction of a foot pound energy per pellet may be all that is required to kill a bird the size of a sparrow and this kinetic energy may be retained to 40 yards or beyond. It is for the purposes of shooting very small birds, therefore, that it is remains commercially-viable for the Italian makers listed above to produce (some very fine) shotguns in 9mm and 8mm rimfire chamberings.

The advantages of very small shot (and therefore of 9mm Flobert cartridges) are not limited to appropriateness to quarry. #12 shot will kill pest birds and rodents but will not blow holes through the walls and roofs of farm buildings constructed from corrugated steel in the way that a cloud of #6 will. They will not embed themselves into the bark or living wood of fruit trees, poisoning the tree and contaminating the fruit. They will not carry any significant distance. This makes garden guns suitable for use in relatively populated or enclosed areas where even a .410 or an air rifle would be “too much gun”.

Looking Back

Although practical uses for the garden gun and its tiny shot are somewhat limited today, at least in the UK, it was not always the case. We know from the historical record that Victorian taxidermists, trying not to damage the animal with which they intended to work, would use tiny charges of #9 and smaller shot, fired from a small bore gun, to stun or kill the animal without materially damaging the carcass.

This practice overlapped with contemporary European practice where the taxidermist’s art was considered to be at least as dependent upon his skill to call his prey within range (10-20 yards, for a stationary shot) as his ability to skin and mount the creature in a realistic fashion.

Other, more obscure examples of the use of garden guns (or very small bore shotguns) exist in the historical record.

A miniature Purdey shotgun, firing cartridges apparently similar in design to Flobert shot shells, but much, much smaller was gifted to King George V on the occasion of his Silver Jubilee. The gun was fully functional and cartridges were made by Eley-Knoch; they were around ½” long and loaded with 1.62 grains of powder and 2.02 grains of dust shot. Apparently the King used the gun to shoot moths, an idea he perhaps inherited from Albert Stewart Meek, an Edwardian naturalist, who used a small bore shotgun – possibly a garden gun – to obtain specimens of some of the largest butterflies found in the world on his expeditions to Papua New Guinea in the early 20th century.

Another anecdote, for which we have not yet discovered any hard evidence, is that the then Lord Walsingham provided the Natural History Museum with its first collection of hummingbirds in the early nineteenth century: all were apparently shot with rimfire shot cartridges loaded with dust shot – perhaps from a garden gun.