Express 28g No 7.5s plastic wad and fibre wad compared


Introduction.

I have heard it said that the plastic wad and cup was the biggest advance in shotgun ballistics since the choke was invented. However, some ranges insist on the use of fibre wads (it is worth noting that although some plastic wads are photodegradable, this is not the same as biodegradable). Shooters often see fibre wads as a disadvantage. The reasons cited are shot deformation when it passes through the forcing cone and choke, galling of the lead as it speeds down the bore and the wad running into the back of the shot once it has left the barrel. The common belief is that plastic wads are much superior.

To test for the differences in patterning Express ProComp 28g 7.5 plastic wads are compared with Express ProFibre 28g 7.5 fibre wads. From the Express website both have a claimed muzzle velocity of 1400fps and shot with 3% antimony. Both are mid-priced shells. The pellet count from unfired shells was 368 for the fibre and 377 for the plastic wad which is close enough to allow direct comparisons of the pellet coverage.

The gun used for the test was a 30" Browning B25 with Teague screw-in chokes. 1/2 choke was used for the tests being a common choice for sporting shooters and (with luck) enough constriction to start to show any ill-effects of the unprotected fibre wad shot being misshaped by the choke.

 


Individual patterns and average pattern width. 

Fibre wad patterns and spread summary.
 Patterns and overall summary of Express ProFibre 28g No7.5 fired from 25yds.
Average Spread
Average shot to shot variation

19.5"

+/- 1.17" (6%)

    

 Plastic wad patterns and spread summary.
Patterns and overall summary of Express ProComp plastic wad 28g No7.5 fired from 25yds.
Average Spread
Average shot to shot variation

17.69"

+/- 1.25" (7.1%)

 

It can be seen that the average spread of the plastic wad shells at 17.69" is about 10% tighter than that of the fibre wads at 19.5" (the spread figure is the diameter that accounts for 75% of the pellets). 

Although not shown here, the fibre wad spread is near to the average spread of many other plastic wads that have been tested. It is this particular Express plastic wad shell that is throwing a tighter than normal pattern.

In practical terms it makes little difference. Unless one needs the extra couple of yards offered by the tighter pattern, the extra spread of the fibre wad will help with a wider pattern. 

 


Analysis of shot to shot repeatability.  

The repeatability of spreads of +/- 6% and +/- 7.1% for the fibre and plastic wad respectively are both very good. However, it should be borne in mind that this is an average spread, the extreme variation is obviously much larger. This is why it is always necessary to average several patterns. Shown below is a plot of the shot to shot spreads where the average, extreme variation and typical variation can be seen.

The conclusion of these tests is that both shells are very repeatable. The range of shot to shot repeatability for other shells tested ranges from a low of +/- 5.5% to the highest at +/- 14%, again these are average shot to shot variations. The extreme spread can be much higher.  

 

 


 

Quality of the patterns.

Because both shells have a similar pellet count and very similar variations in shot to shot spread, with a sleight of hand it is possible to directly compare the relative coverage of the two sets of patterns. The trick is to re-scale one set of patterns to the give the same average spread as the other. Next, passing a simulated edge-on clay across the pattern and finding the probability of a pellet striking it can reveal any gaps in the pattern (possibly caused by the wad ramming into the shot soon after leaving the muzzle).

The fibre wad patterns were rescaled to 35yds to simulate a more open pattern - probably about the limit for this shell and choke combination and the plastic wad loads were rescaled to 38.61yds so that they have the same average spread.

Shown below is an example of how such a more open pattern looks.

 

Express ProComp 28g No7.5 (plastic wad) fired at 25yds, rescaled to simulate 38.61yds.

 

Looking at the pattern data below, it can be seen that the patterns over the 9-shell average are almost identical. The distribution of pellets in the 10", 10-20" and 20-30" areas are almost identical. Similarly the probability if hitting the small area of an edge on clay is almost identical. What this means is that there is no evidence of the fibre wad shells having inferior patterns. This includes any effects of the wad affecting the centre of the pattern or shot deformation leading to more fliers.

 

Summary of pellet distribution and pattern performance of Express ProFibre shot at 25yds, scaled to 35yds.

 

Summary of pellet distribution and pattern performance of Express ProComp (plastic wad) shot at 25yds, scaled to 38.61yds.

 


 

Summary and post-amble.

In terms of quality of pattern, there is nothing to separate these two shells. There is the possibility that there may be differences at extended range using tight chokes. This is a future test.

To date only two types of fibre wad have been tested, this Express ProFibre and also a Hull Cartridge ProFibre 28g No.9 (see separate report). In both cases the fibre wads give excellent repeatability of spread. Plastic wads by comparison offer the best and worst in performance. 

A theory of how plastic wads affect pattern width and repeatability.

A deduction from this is that the main detriment to repeatability of spread is not pellet deformation during powder ignition, or passing through the forcing cone, or through the bore and choke, but the launch conditions of the pellets. In the case of a fibre wad, the muzzle determines the launch conditions. It is made of steel and very repeatable! With plastic wads, however, there is the added variable of how the wad behaves just as it traverses the muzzle and then how it opens in flight. I have seen many shot wads lying on the ground that have only partially opened which suggests the process can be very variable. 

I'm also wondering if the reason some plastic wad shells group tighter is not because they are deforming the shot less that leads to better aerodynamic properties of the pellets, but rather because they are delaying the point at which the shot becomes free flying and hence moving the whole pattern a yard or two further up-range. 

These ideas are also tentatively supported by the results from the skeet gun comparing No.9 shot where the plastic wad shell gave widely varying spreads but also gave a tighter spread on average, i.e. sometimes the shot cup opened early, and sometimes it didn't.

Both the graph above showing the shot to repeatability and the similar graph for the skeet gun show the plastic wad grouping tighter on average than the fibre wad. However, in both cases the widest patterns from the plastic wad are very near the average of the fibre wads. This also tentatively suggests that the maximum spread from the plastic wad is when the wad opens straight away, and when this happens the spread is close to that of the unconstrained fibre wad. However, if the wad delays opening, the pattern at a given range appears a little tighter. A few plastic wad shells achieve the feat of moving the pattern up-range without ruining the repeatability. Unfortunately, some don't!  

Implications of wad performance on the wisdom of backboring.

If fibre wads do have an advantage it calls into question the merits of backboring. Even the proponents of backboring say that it is not compatible with fibre wads because they risk not making a good gas seal (unlike the skirt on a plastic wad that can expand). Given this I would not be wanting backboring on my gun - especially if a particular range or event mandates that fibre wads must be used. The same argument applies regarding extended forcing cones. Both backboring and extended forcing cones seem (to me) to claim small gains that are seldom proved but acknowledge risks that can be profoundly bad for the shell performance. 

Next steps.

More fibre wad loads need to be tested. At a personal level, if on average they behave in a more repeatable way then I will move over to them. 

The performance of plastic wads is questioned in colder weather and also the manufacturers can change wad supplier and the shooter would be none the wiser. If plastic wad performance can make the difference between excellent or terrible repeatability, personally, I'd rather remove this gross uncertainty and settle for the 'safe pair of hands' of a fibre wad. They might not offer the ultimate in range, but repeatable pattern width is more use to me. 

This is particularly so if the clay is close. Incomers at skeet can be 5-7yds away. If a plastic wad fails to open there will be almost no spread whereas the fibre wad could be giving up to 10" diameter spread. That's quite a difference.


 
 
 
 
 
 
   

(c) Dr A C Jones