An article exploring, via empirical testing, the affliction affectionately known to the members of the SmallBoreShotguns team as “The English Disease”.
Abstract & Conclusions
The SmallBoreShotguns team believed, on the basis of a) past experience, b) analysis of data collected for this website and c) physical modelling, that high velocity (i.e. V0 = 1400fps+) cartridges offer no performance advantage over equivalent loadings of more moderate velocity (V0 = 1150-1300fps) and are very likely produce inferior performance because of pellet damage caused by accelerating a shot column to such velocities.
This hypothesis was shown to be broadly true: the pattern data collected appears to give the advantage to the subsonic loading although the effect is perhaps not clear cut and requires some interpretation. This is discussed in the “Analysis” section below.
Background
High velocity (see above) cartridges are often advertised and sold as the “most potent” loadings in the English market and command a high price compared to what many of us would consider more run-of-the-mill cartridges. At the time of writing, an ordinary “game” load from any of the UK manufacturers will cost in the region of £7-9 per box, whereas top-of-the range loadings specifically marketed for “speed” are often £10, £12 or even £15 per box.
There are a handful of occasions when, in the view of the SBS team, high muzzle velocity is justified. The most obvious example is in the case of ammunition for wild fowling, where high muzzle velocity is often the only available means of overcoming the lower density of steel shot and the corresponding loss of kinetic energy faster deceleration this causes.
On the other hand, when Edward VII and George V were shooting four-figure bags in the early 20th century with their Damascus-barrelled black powder guns, muzzle velocities of 900fps were by no means unusual. Loadings were perhaps a little heavier – 1¼oz in a 12 gauge would have been more common than the modern “light” loadings – but shot sizes, if anything, tended to be smaller. This begs the question: how did they shoot so effectively when ammunition was apparently so much less advanced than the cartridges we enjoy today?
The SBS team believe that the reasons for the effectiveness of these early loads are probably threefold.
Firstly, expectations of pattern density in the early 20th century were that much higher: there are around 400 pellets in 1¼oz of English #7 shot and this was considered a perfectly ordinary loading. Very few birds could escape even a 50% 40-yard pattern from such a cartridge and this kind of density brings into play the likelihood of central nervous system strikes providing “instant kills”. Pellets may not have always penetrated through to the vital organs in the chest cavity at long range, but they probably still impacted something significant.
Second, shooting ranges were usually shorter. It is not just the English who today expect to use their shotguns at ranges of 50, 60 or even 70 yards, but that is certainly the expectation of many folk with whom the SBS team have contact. Undeniably, smokeless powder and improved designs have made this possible in some situations in a way that was not possible 100 years ago – but we do not necessarily attribute this to increased muzzle velocities.
The third reason – of most significance to this article – is really an extension of the first. Not only were early 20th century loads significantly heavier, but – we believe – they patterned significantly better both in terms of overall pattern size and evenness due to their lower muzzle velocities. This view is supported by a small but growing number of present-day reloaders who have begun to look at the benefits of subsonic shotgun rounds and found somewhat astounding results: overall patterns only 2/3 of the size of an “ordinary” pattern at any given range.
A Test Method
Reader, you may be assured that we would not simply rely upon others to tell us that any given theory was correct or otherwise, where we have the opportunity to test it ourselves. Thus, we concocted the following experiment.
Two 12-gauge clay cartridges, both containing 28g of #7½ shot, one subsonic and one at the top of the “speed” market, from the same manufacturer were patterned six times each at a distance of 30 and 40 yards through the 3/8-choke (0.017″ constriction) barrel of a Baikal IJ-58 side by side shotgun. Pellet counts for a number of unfired cartridges were made and an average calculated.
For each pattern, for each cartridge, the number of pellets falling within a 30″ circle covering the densest part of the pattern was determined. An estimate of the overall pattern width was also made. These counts and pattern widths were then combined to give an average absolute and percentage performance and average overall widths for both cartridges.
Data
The following table describes the data obtained during the experiment.
| Distance | Cartridge | 30" Circle Impacts (Total) | Percentage Performance (Nominal) | Estimated Pattern Diameter |
|---|---|---|---|---|
| 30 Yards | Hull "Subsonic" 28g/#7½ | 348 (360) | 97% (Extra Full) | 26" |
| 30 Yards | Hull "Subsonic" 28g/#7½ | 336* (360) | N/A* | N/A* |
| 30 Yards | Hull "Subsonic" 28g/#7½ | 324 (360) | 90% (Full) | 28" |
| 40 Yards | Hull "Subsonic" 28g/#7½ | 269 (360) | 74.8% (Extra Full) | 38" |
| 40 Yards | Hull "Subsonic" 28g/#7½ | 270 (360) | 75% (Extra Full) | 38" |
| 40 Yards | Hull "Subsonic" 28g/#7½ | 221* (360) | N/A* | N/A* |
| 30 Yards | Hull "Sovereign" 28g/#7½ | 342 (376) | 91% (Full) | 29" |
| 30 Yards | Hull "Sovereign" 28g/#7½ | 353 (376) | 94% (Full) | 28" |
| 30 Yards | Hull "Sovereign" 28g/#7½ | 352 (376) | 94 (Full) | 29" |
| 40 Yards | Hull "Sovereign" 28g/#7½ | 258 (376) | 69% (Full) | 41" |
| 40 Yards | Hull "Sovereign" 28g/#7½ | 235 (376) | 62% (Modified) | 39" |
Variables
Before posting our analysis, we mention the following variables which may have affected the test.
- The Subsonic cartridge contains a plastic wad, as opposed to the Sovereign’s fibre wad. A plastic wad is usually seen as a performance advantage, though this is not necessarily the case.
- The Subsonic cartridge is packaged in a box of an old design, suggesting that they are some years older than the newly re-branded Sovereigns. We do not think that age is of particular significance to shotgun cartridges, but if the Subsonic cartridge is older and its powder has degraded (very doubtful) then it is possible that it will produce lower muzzle velocities than expected. This may highlight any differences between the cartridges or exaggerate the effect of lower velocity.
- In the opinion of the SmallBoreShotguns team, hardness of shot is a highly significant factor in cartridge performance. The Subsonic cartridge has “ordinary” 2% antimony shot; the Sovereign contains 5% antimony shot which is considerably harder. If this were the only difference, we would expect the latter cartridge to perform significantly better.
- Both cartridges appear to contain shot which is slightly larger than a nominal #7½. In the case of the Subsonic cartridge, this is likely to be a deliberate decision on the part of the designers, to compensate for the lower-than-usual muzzle velocity. In the case of the Sovereigns, the effect may be for the same reasons: to increase potency at range.
Analysis
A strict reading of the data, including the “off-centre” patterns but without making any allowances for the fact that there were undoubtedly more pellets within the 30″ circle than were recorded on the paper, gives the following overall results:
| Cartridge | Distance | Mean Pellet Count (Total) | Mean Percentage | Mean 90% Pattern Width |
|---|---|---|---|---|
| Hull "Sovereign Fibre" 28g/#7½ | 30 Yards | 349 (376) | 92.8% | 28½" |
| Hull "Subsonic" 28g/#7½ | 30 Yards | 336 (360) | 93.3% | 27" |
| Hull "Sovereign Fibre" 28g/#7½ | 40 Yards | 246 (376) | 65.4% | 40" |
| Hull "Subsonic" 28g/#7½ | 40 Yards | 253 (360) | 70.3% | 38" |
These data demonstrate that, even having the advantage of significantly harder (5% Sb) shot and – one assumes – superior powder and other components, the top-of-the-range Sovereign cartridge can only just match the performance of the Subsonic cartridge at 30 yards and falls short by a 5% margin at 40 yards. The Sovereign loading does achieve slightly higher absolute pellet counts, but this is somewhat redundant given the large margin over and above the 180-200 pellets generally required in the circle for sporting clays.
Admittedly, these results are by no means clear cut.
The data also show that the average pattern width (calculated by ignoring the 10% outermost pellets in the pattern and measuring between the two farthest-apart remaining marks) is marginally greater for the supersonic Sovereign loading. This is not unexpected.
It would be legitimate, however, to either account for, or discard the patterns which were not captured completely. If we choose to account for them, rather than ignore them, we must calculate the missing area and make an estimate of the number of pellets which would have fallen inside the circle had the pattern plate captured the whole pattern.
We can either make an estimation of the number of pellets not captured empirically, by cutting a piece of cardboard of the missing size, placing it over another section of the pattern and counting the number of holes covered, or mathematically, using the formula for the area of a chord, given below:
If we do this for the two Hull Subsonic patterns which were off-centre, using both methods, we receive the following results:
| Distance | Height of Chord | % Missing Area | Predicted Total Count | Empirical Average |
|---|---|---|---|---|
| 30 Yards | 3½" | 6.5% | 359 | 353 |
| 40 Yards | 5" | 10.9% | 248 | 241 |
Using the empirical (i.e. more conservative) averages leads us to the following counts and percentages:
| Cartridge | Distance | Mean Pellet Count (Total) | Mean Percentage |
|---|---|---|---|
| Hull "Sovereign Fibre" 28g/#7½ | 30 Yards | 349 (376) | 92.8% |
| Hull "Subsonic" 28g/#7½ | 30 Yards | 346 (360) | 96.1% |
| Hull "Sovereign Fibre" 28g/#7½ | 40 Yards | 246 (376) | 65.4% |
| Hull "Subsonic" 28g/#7½ | 40 Yards | 260 (360) | 72.2% |
Here we see the gap start to widen between the Subsonic and Sovereign loadings, with the Subsonic cartridge showing superior performance at both 30 and 40 yards. Although this degree improvement is within the normal shot-to-shot percentage variation for an ordinary cartridge, which would make further testing valuable, the fact that the figures are averages increases confidence in our conclusion.
Alternatively, we can simply ignore the off-centre patterns altogether, which gives the following results:
| Cartridge | Distance | Mean Pellet Count (Total) | Mean Percentage |
|---|---|---|---|
| Hull "Sovereign Fibre" 28g/#7½ | 30 Yards | 349 (376) | 92.8% |
| Hull "Subsonic" 28g/#7½ | 30 Yards | 342 (360) | 95.0% |
| Hull "Sovereign Fibre" 28g/#7½ | 40 Yards | 246 (376) | 65.4% |
| Hull "Subsonic" 28g/#7½ | 40 Yards | 269 (360) | 74.7% |
Here the advantage of the Subsonic cartridge is clear to see. The 40-yard pattern density for the Subsonic cartridge exceeds by a clear 9% margin, the pattern density for the faster Sovereign brand. In sporting clays, this may not be enough to make a difference, but translate that advantage to a hunting situation and a cartridge containing only 200 pellets to start with: an 9% increase in pattern density changes an adequate pattern (122 / 30″ circle) into a good pattern (140 / 30″ circle) or gives as much as 5 yards of extra effective range – not to be sniffed at.
Remember too, that the aforementioned 9% advantage of the Subsonic cartridge represents the average difference in performance. The absolute improvement from worst to least is on the order of 12%, which represents more than a whole degree of choke in most people’s estimation. This may not be so significant in the average 12-gauge cartridge, but for the small bore shotgunner in search of a 40-yard round, it is of huge importance.
Furthermore, let us return to the qualification we mentioned above. The shot in the Sovereign cartridge is significantly harder than ordinary shot and therefore less prone to deforming. If we were to launch more-ordinary 2% antimony shot from the Sovereign cartridges, pellet damage would be further increased, more fliers generated and – we suspect – the differences in pattern density might open up to 15% or even perhaps 20%! Put another way: the engineers at Hull are having to work very hard to keep the performance of their “super quick” top-of-the-range cartridge in the same ballpark as their “beginners” load.
A final thought: one interesting difference between the two loadings is apparent from the patterns. With the subsonics, the best pattern was 97% of the original load at 30 yards (348/360) and (we assume) every pellet which flew out was still on the paper, if not in the circle. (Note that 360 is the average pellet count – there are in fact 18 marks outside the circle shown in the image below).
The Sovereigns on the other hand, never managed better than 93% and averaged 89% (336/376) and probably only half of the “missing” pellets still hit the paper. That difference in speed is essentially the same as dropping 5% of the load on the floor before you fire it – you simply never see them again.
Example Patterns
