ROSE

A shot pattern is the distribution of impacts produced on the target by a load of shot or, in rifled firearms, the set of holes created by multiple projectiles fired under the same conditions. In smoothbore guns, it allows us to evaluate the width, density, uniformity, and position of the swarm; in rifles and handguns, it primarily indicates the accuracy and repeatability of the gun-ammunition system. A good shot pattern isn't necessarily the tightest: it must be regular, sufficiently dense, and suited to the distance and intended use.

WHAT IS ROSATA?

In hunting language, the term "shot pattern" mainly indicates the arrangement of the pellets on the target after firing a split-shot cartridge.

As it travels through the barrel and immediately after exiting the muzzle, the shot load doesn't remain compact. It gradually transforms into a swarm that increases in diameter and length with distance.

The pattern left on the target represents a two-dimensional section of this three-dimensional phenomenon. By observing it, you can evaluate how the barrel, choke, cartridge, wad, and pellets work together.

In rifled shooting, the same term is used to indicate the grouping obtained by firing multiple shots towards the same aiming point.

THE PATTERN IN SMOOTH-BORED WEAPONS

In smoothbore guns, the pattern is formed by dozens or hundreds of pellets. The quantity depends on the pellet diameter, material, caliber, and overall weight of the load.

Once they exit the muzzle, the pellets gradually separate. Some remain in the center of the swarm, while others move toward the periphery.

The quality of the rose is normally evaluated by considering:

• overall diameter;
• impact density;
• uniformity of distribution;
• presence of voids;
• central concentration;
• position relative to the targeted point;
• repeatability between multiple cartridges.

THE SWARM OF SHOTGUN

The pattern visible on the map does not match the entire swarm of pellets . The swarm actually has width, height, and depth.

The pellets don't all reach the target at the same time. Those that remain relatively regular and close to the front of the charge tend to remain faster; those that are deformed or deflected can slow down and settle towards the rear of the swarm.

The swarm then takes on an elongated shape, often simplified as a cloud or spindle. Its length tends to increase with distance.

The pattern on a stationary target registers all impacts on the same plane, without showing differences in the time of arrival.

CENTER AND OUTSKIRTS OF ROSATA

The distribution of pellets is not usually uniform throughout. The center tends to be more concentrated, while the impacts become more sparse as you move outward.

In general, we can distinguish:

• central core: area with the highest density of pellets;
• intermediate band: area in which density progressively decreases;
• outskirts: external area with more spaced and irregular impacts.

There is no clear boundary between these areas. Density gradually decreases from the center toward the edge of the band.

DIAMETER AND DENSITY

The pattern diameter describes the size of the impact area. A wider pattern covers a larger surface area, but distributes the pellets over a wider area.

Density, on the other hand, indicates how many pellets reach a given surface. For the same number of pellets, a tighter pattern will generally be denser.

A very wide pattern can facilitate the interception of a close, fast-moving target, but it may have gaps and insufficient density. A very tight pattern, on the other hand, maintains greater density at longer ranges, but requires more precise aiming at close ranges.

THE UNIFORMITY OF DISTRIBUTION

A quality shot pattern should distribute the pellets with a certain regularity, without excessive crowding or large areas completely devoid of impact.

Gaps are particularly important when they are large enough to allow a vital portion of the game to pass through the shot pattern without being hit by an adequate number of pellets.

A very narrow but irregular pattern may be less effective than a slightly wider but better distributed one.

Uniformity must be evaluated over multiple shots, because a single cartridge may produce a pattern that is randomly more regular or more irregular than the average pattern.

THE BOTTLING

Choke is the controlled reduction of the barrel's internal diameter near the muzzle. Its main function is to influence the dispersion of the shot swarm.

A more open choke generally tends to produce wider patterns at shorter ranges. A tighter choke maintains a higher concentration at longer ranges.

Traditional names include:

• Cylinder or cylindrical;
• Improved Cylinder;
• Modified;
• Improved Modified;
• Full.

In the European classification, stars are also often used, generally from five stars for the most open constriction to one star for the most closed ones.

NOMINAL CHOKE AND REAL PATTERN

The designation engraved on the barrel or choke does not allow you to predict the pattern behavior with absolute certainty.

Two choke tubes with the same rating can produce different results due to the internal geometry, cone length, actual bore diameter, and the cartridge used.

The nominal choke is therefore an indication, while the target test shows the actual result of the combination.

THE DISTANCE

Distance is one of the factors that most influences pattern distribution. Immediately after the muzzle, the pellets are still relatively close together; as they travel further along the trajectory, the swarm widens and lengthens.

As the distance increases:

• the diameter of the spray increases;
• decreases the density of impacts;
• increase the spaces between the dots;
• decreases residual speed;
• the swarm grows longer;
• increases the influence of the wind.

The useful distance therefore does not depend only on the ability of the pellets to reach the target, but on the combination of pattern density and residual energy.

THE NUMBER AND DIAMETER OF THE SHOTGUN

For the same load weight, smaller pellets are present in greater numbers. They can therefore produce a pattern with more impacts and more uniform coverage.

Larger diameter pellets are fewer in number, but each has a greater mass and tends to conserve energy and velocity better.

The choice must find a balance between:

• number of impacts;
• uniformity of coverage;
• residual energy of the single pellet;
• size and resistance of the wild animal;
• expected distance.

A larger pellet does not automatically guarantee greater effectiveness if the pattern becomes too sparse.

THE WEIGHT OF THE CHARGE

A heavier load generally contains a greater number of pellets of the same diameter. This can increase the density of the pattern, but it doesn't necessarily mean a more uniform distribution.

The increased number of pellets increases the length of the column inside the cartridge. During acceleration, the pellets located at the bottom can experience higher pressures and deform more.

A heavier load can also produce more recoil and alter the overall behavior of the ammunition. The quality of the pattern depends on the design of the cartridge, not just the indicated weight.

THE DEFORMATION OF THE SHOTGUN

Perfectly spherical pellets exhibit more regular aerodynamic behavior. When squashed or deformed, they encounter uneven resistance and can move further away from the center of the swarm.

Deformation can occur during:

• the rapid acceleration in the cartridge;
• the passage through the connecting cone;
• the sliding along the barrel;
• crossing the bottleneck;
• contact between pellets of the same charge.

The hardness of the material, the protection offered by the wad and the construction quality of the cartridge help to limit these deformations.

HARD LEAD, SOFT LEAD AND ALLOYS

Lead shot can be produced with varying percentages of alloying elements. Harder lead resists deformation better and tends to maintain a more regular shape.

Softer pellets can deform more during firing, increasing the presence of peripheral elements in the pattern.

The result, however, depends on the entire system: velocity, pressure, weight of the charge, wad, barrel geometry and choke.

STEEL SHOTGUN

Steel shot is harder and less deformable than lead, but has a lower density. For the same diameter, it is lighter and loses velocity and energy more quickly.

Their rigidity can produce relatively tight patterns. For this reason, chokes used with steel must be compatible with the ammunition and the weapon.

The container wad takes on particular importance because it protects the barrel from direct contact with the pellets and controls their passage through the choke.

BISMUTH AND TUNGSTEN SHOT

Bismuth has a density closer to that of lead than steel, but has different mechanical characteristics and can be more brittle.

Tungsten-based alloys can achieve high densities and retain energy and velocity well. Their patterning behavior depends on the formulation, shot diameter, and cartridge construction.

Different materials shouldn't be compared based solely on the nominal pellet number. Density, hardness, and aerodynamic behavior affect actual performance.

THE WASTE

The wad separates the powder from the shot charge, helps seal the gases and accompanies the swarm in the first part of its movement.

A container wad envelops the pellets with special fins and reduces direct contact with the barrel. This can limit deformation and keep the swarm more compact.

A traditional wad without a container allows the pellets to come into contact with the core sooner and generally tends to promote faster dispersion.

There are also wads designed to delay the opening of the charge or to produce a wider dispersion at short distances.

DISPERSING WADS

Spreader wads are designed to increase the spread of the shot, especially at close ranges.

They can use dividing elements, particular geometries or systems that intentionally disturb the arrangement of the charge.

They are used when an excessively concentrated shot pattern would make it more difficult to hit a fast, close target. The actual effect varies depending on the barrel and choke and must be verified on target.

CARTRIDGE SPEED

A high initial velocity reduces flight time, but subjects the charge to a greater acceleration. The increased stress can deform the pellets and disrupt the swarm.

A faster cartridge does not automatically produce a better pattern. In some combinations, it can increase peripheral dispersion.

Performance depends on the balance between pressure curve, powder type, wad, shot hardness and barrel geometry.

THE CONNECTING CONE

The cone connects the cartridge chamber to the bore of the barrel. As it passes through, the charge is guided from a larger diameter to the smaller diameter of the barrel.

The length and geometry of the cone can influence the stresses exerted on the pellets and the wad.

A progressive transition can limit some deformations, but the quality of the pattern always depends on the overall behavior of the system.

THE INTERNAL DIAMETER OF THE BARREL

Barrels of the same caliber may have slightly different internal diameters within the expected tolerances. The relationship between bore, wad, and choke affects the way the charge is compressed and guided.

Back-bored barrels use a larger internal diameter than more traditional configurations. They can reduce some deformation and alter the pattern response, but the results must be evaluated with the specific ammunition.

The nominal diameter alone does not allow us to predict the distribution of impacts with certainty.

THE POSITION OF THE ROSE

In addition to width and density, you need to check where the center of the shot is located in relation to the aimed point.

A shotgun may distribute pellets evenly but place the core too high, low, or to the side.

The position depends on the alignment of the barrels, the stock, the way the gun is shouldered and the relationship between the rib, the front sight and the shooter's eye.

In double-barreled guns, the pattern produced by each barrel must be evaluated separately.

CONVERGENCE IN DOUBLE-BARRELLED WEAPONS

In side-by-side and over-and-under shotguns, the barrels aren't simply two perfectly parallel tubes. They're assembled and adjusted so that their respective pattern centers are compatible with the distance specified in the design.

Convergence does not necessarily mean that both centers coincide at exactly the same point. The goal is to obtain a functional relationship between the two distributions.

An excessive difference between the groups of the two barrels may depend on the adjustment, the ammunition or a mechanical problem and requires a specialist check.

HOW TO TEST A ROSE

The test must be performed on a sufficiently large target, placed at a known distance. The aiming point must be clearly visible, and the weapon must be used under controlled conditions.

To achieve a significant result, it's necessary to fire multiple rounds of the same type, preferably on different papers. A single grouping doesn't necessarily represent the average behavior of the combination.

After the shot, the actual center of the distribution is identified and the area used for counting is traced around it. The scoring circle should not automatically be centered on the targeted point, because the quality of the distribution must be distinguished from any shift in the point of impact.

THE EVALUATION CIRCLE

Ballistic tradition often uses a reference circle approximately 75 centimeters in diameter, corresponding to 30 inches, to evaluate the percentage of pellets contained in the pattern at a given distance.

The method allows for comparison of cartridges and chokes, but should not be applied rigidly to any range or purpose.

For the hunter, it can be useful to combine the percentage count with a practical evaluation of the voids and density in the dimensions corresponding to the vital area of ​​the game being considered.

THE PERCENTAGE OF PINK

The pattern percentage compares the number of pellets inside the reference circle to the total number contained in the cartridge.

To calculate it, you need to know or determine the total number of pellets in the charge. The impact count in the circle is then expressed as a percentage of the total.

A high percentage indicates that a greater portion of the charge remained concentrated in the area under consideration. However, it does not, by itself, describe the uniformity of the distribution.

Two shots with the same percentage can have very different impact patterns.

COUNTING THE SHOTGUN

The theoretical number of pellets can be estimated based on the weight of the charge, the diameter, and the density of the material. However, the actual number may vary due to dimensional and manufacturing tolerances.

For a particularly accurate evaluation, it is possible to directly count the pellets of a cartridge belonging to the same batch, without assuming that all the loads contain exactly the same number.

Comparing ammunition made of different materials requires care, because pellets of the same diameter can have very different masses.

THE RULE OF QUADRANTS

To assess uniformity, the pattern circle can be divided into sectors or quadrants. The number of impacts in the different areas is then compared.

Large differences between sectors may indicate an uneven distribution or a shift of the real center with respect to the drawn circle.

The subdivision allows you to more easily identify excessively sparse areas, concentrations and asymmetries.

REPEATABILITY

Every pattern contains a random component. Even identical cartridges fired from the same barrel do not produce a perfectly overlapping pattern.

To evaluate a combination it is therefore necessary to observe several rosés and look for recurring characteristics:

• average diameter;
• central density;
• number and size of voids;
• downtown location;
• possible presence of very peripheral pellets.

Quality should be judged on the overall trend, not on the exceptionally good or bad performance of a single cartridge.

THE WIND

The wind acts on the individual pellets, gradually moving the swarm. Because pellets have a limited mass and ballistic coefficient, they can be sensitive to even moderate winds.

As the distance increases the wind can:

• move the center of the shot laterally;
• increase dispersion;
• accentuate the elongation of the swarm;
• reduce the useful density on the target.

Smaller, lighter pellets are generally affected more quickly than larger diameter pellets.

TEMPERATURE AND ATMOSPHERIC CONDITIONS

Temperature changes air density and can affect powder combustion. The effects on pattern are usually less noticeable than those caused by choke, cartridge, and distance, but they can contribute to differences between summer and winter conditions.

Rain and vegetation may interfere with individual pellets, but they should not be imagined as a uniform barrier capable of immediately stopping the entire swarm.

Weather conditions become more important as distance increases and residual speed decreases.

THE GAUGE IN RIFLED WEAPONS

In rifles, the term "pattern" describes the group formed by multiple shots fired at the same point. Therefore, it doesn't evaluate the distribution of numerous pellets from a single cartridge, but rather the repeatability of a succession of projectiles.

Dimensions can be expressed in:

• millimeters or centimeters;
• inches;
• MOA;
• MRAD.

Linear measurement is only meaningful if the distance is also indicated. A 30-millimeter group at 50 meters is not equivalent to the same size obtained at 100 or 200 meters.

HOW TO MEASURE A RIFLE GROUP

The most common measurement is taken between the centers of the two furthest holes. In practice, you measure the maximum external distance and subtract the bullet diameter.

This method describes the overall size of the group, but can be strongly influenced by a single shot far from the others.

More in-depth analyses use mean radius or other statistical methods, which can better describe the overall distribution of impacts.

PRECISION AND ACCURACY

A tight pattern indicates that the shots are concentrated, but not necessarily that they are on the aimed point.

It is useful to distinguish:

• precision: ability to group shots together;
• accuracy: proximity of the group to the desired point.

A group may be accurate but off-center. In this case, the gun may require zeroing. A very scattered group, however, cannot be corrected simply by moving the reticle.

THE NUMBER OF SHOTS

A small group of shots provides limited information. Three shots can provide a first indication, but larger groups better describe the system's true dispersion.

As the number of shots increases, the probability of recording the entire variability of the weapon, ammunition and shooter also increases.

However, in light hunting rods, heating must be taken into account, as it can change the point of impact during prolonged series.

THE SHOT OUT OF THE ROSE

An impact distant from the main group is often referred to as a flyer . It should not be automatically excluded from the measurement.

The stroke may depend on:

• shooter's error;
• ammunition variation;
• heated barrel;
• non-constant support;
• gust of wind;
• problems with optics or mounts;
• bullet defects;
• irregular contact between barrel and stock.

A stroke can only be ruled out when there is a clearly identifiable and documented cause.

THE PATTERN DOESN'T JUST DEPEND ON THE WEAPON

Impact distribution is the result of the entire system. In smoothbore guns, it includes the barrel, choke, cartridge, pellets, wad, and distance.

In rifled weapons, bullet quality, velocity, twist rate, barrel condition, bedding, optics, support and shooter technique also play a role.

It is therefore incorrect to automatically attribute an unsatisfactory pattern to a single component without carrying out comparative checks.

A cliché to be cleared up

The best pattern isn't always the tightest. When shooting pellets, excessive concentration can reduce the margin for error at short ranges and result in a very high number of impacts in a limited area.

Conversely, a very open pattern may seem advantageous because it covers a larger surface area, but it may be too sparse to ensure an adequate number of impacts.

The shot pattern must be evaluated based on the distance and the type of game, seeking a balance between width, uniformity, density and residual energy.

DID YOU KNOW THAT?

• The target pattern is only a section of the three-dimensional swarm.
• The pellets do not all reach the target at the same time.
• A choke with the same designation may produce different results on different barrels.
• A high percentage does not automatically guarantee even distribution.
• Deformed pellets tend to move further away from the center of the swarm.
• The wind can move the center and change the shape of the pattern.
• The two barrels of a side-by-side or over-under shotgun must be evaluated separately.
• In rifled weapons a tight pattern may be precise but not accurate.
• Three shots do not always describe the entire dispersion of the system.
• A single grouping is not enough to judge a gun-cartridge combination.

FOR THE HUNTER

The pattern test allows you to understand the actual behavior of your shotgun with a given cartridge. It's important to test each barrel and choke separately at the ranges intended for use.

You shouldn't just look at the overall diameter. You should also check the location of the center, density, uniformity, and the presence of significant voids.

The test should be repeated with multiple cartridges from the same batch. Changing the brand, wad type, material, shot diameter, load weight, or choke can significantly alter the performance.

A responsible choice must ensure sufficient density and adequate residual energy within realistic distances, avoiding using the swarm beyond its effective limit.

IN SUMMARY

In smoothbore guns, the pattern is the distribution of impacts left by a shot load. Its quality depends on its width, density, uniformity, location, and repeatability.

Choke, distance, shot diameter and material, load weight, wad and barrel geometry all contribute to the final result.

In rifled weapons, the pattern indicates the grouping of multiple bullets and allows for the evaluation of the accuracy of the entire weapon-ammunition-shooter system.

In both cases, the target test represents the only reliable method for understanding the actual behavior of the combination used.