Bioammo MM Rex review

Richard Atkins tests the Bioammo MM Rex cartridges which, for a premium, offer biodegradable wads and cases too.

The fully biodegradable cases have taken ten years of development

Most shooters are all too well aware that shotgun shooting is under growing pressure to improve its eco-friendly credentials. Moves against plastics in the environment increased substantially following the BBC’s ‘Drowning in Plastic’ TV documentary.

Following that programme photographs of plastic wads and the odd cartridge case began to appear on social media and elsewhere, being picked up by some newspapers who produced negative news reports.

The eco-warriors are on the warpath, and plastic wads in cartridges are a key target. These are obviously sent out with the shot load to land some distance away and, in most forms of field or foreshore shooting, are very difficult or impossible to retrieve.

Shooters recognised this aspect quite readily and have, over recent years, turned increasingly to the use of fibre wads in their cartridges. For game and other live quarry shooting, fibre wad cartridge sales exceed plastic wads and, indeed, some cartridge makers have elected to all but eliminate plastic wad options in their 12 gauge cartridge ranges.

Clay shooters are in a slightly different situation. With most of the formal disciplines requiring a standard shooting layout, such as Trap, Skeet, Compak and Sportrap, the landing zone for plastic wads is well defined and in most cases it is possible to collect the accumulated fired plastic wads.


Understanding the test results

  • Velocity is measured at 2.5 metres from the muzzle.
  • Pressure is the mean breech figure in Bar (as per CIP).
  • SD is Standard Deviation (consistency).
  • CD is the Central Density rating. This records the percentage of the total pellets landing in the 30-inch circle that were also within the inner 20-inch circle
  • Shot size is derived from actual pellet count per ounce and is listed to the nearest UK size, with < and > symbols where shot is slightly larger or smaller than the nearest size. UK No.7 = 340 pellets/oz; UK No.7.5 = 400 pellets/oz; UK No.8 = 450/oz; UK No. 9 = 580/oz.
  • Shot weight is the average actual shot load, measured in grains. 1 grain = 0.065 grams = 0.0023 oz. CV is Crush Value. This is the amount by which the shot is reduced in size when subjected to the standard crush test. A smaller value means harder lead, so a CV figure of 20% is harder than 30%, for pellets of similar size. Smaller shot crushes proportionately more than larger size.
  • Choke boring Nominal pattern percentages at 40 yards are: Half Choke 60%; Imp/ Mod (three quarter) choke 65%; Full choke 70%.

However, Sporting layouts are generally on farmland or in woodland, and offer much less chance to collect fired wads – which has led to a majority of Sporting clay grounds insisting on the use of fibre wad ammunition.

Some competitive clay shooters don’t like fibre wad ammunition and many major shooting grounds that hold top tier Sporting clay competitions allow plastic wads, if only for the major events. However, the moves already made towards fibre wads, for their ‘green credentials’, have been steadily increasing in recent years.

The ongoing move toward non-toxic shot is a separate issue, except for the fact that the most affordable option to lead shot, steel, requires a very strong and efficient wad to protect gun barrels and that has raised concerns that plastic wad use could increase.

That was until very recently, when options for biodegradable cup wads became available. Some readers might recall that, back in 2014, Armusa launched a water soluble wad, which at the time we reviewed.

This was obviously a bit ahead of its time, and although it offered the opportunity to use a plastic wad that would disappear into the ground faster than a fibre wad would, neither the shooting grounds nor the shooters showed much enthusiasm for it, and were reluctant to pay the ‘eco premium’.

Last year, however, we saw Eley launch their now expanding range of clay and game cartridges with a similar water soluble wad which, Eley report, people are trying out in numbers.

Bioammo MM Rex 28g 7.7 Shot Biodegradable plastic wad

Shot load437 grains
Pellet (count per oz)353
UK shot (size / CV)<7.5 / 25%
Pellets in 30in dia (Av)233
Pellets in 20-30in 100
Pattern  66%
CD57%
Velocity401 m/s (1,316 fps)
SD7.6
Recoil (M) (unit= Ns)11.24
Pressure (unit = bar)645

Biodegradable cases

So that’s the wads, but what about the fired cases? Many clay grounds are able to collect and recycle their empty cases, but that isn’t the whole answer. Some shooters have suggested a return to paper cased, fibre wad cartridges with their more ‘eco-friendly’ appeal. I do, however, feel that this is unlikely to happen. 

Paper cartridge cases have a number of drawbacks which shooters were happy leave behind once plastic cases became available. The capacity no longer exists to produce the volume of paper cased cartridges that would be required to replace the millions of plastic cases used each year. And this is where Bioammo Srl of Segovia, Spain, has an ace in its hands – fully biodegradable cartridge cases!

Bioammo has spent more than ten years researching, developing and now finally producing a new and different type of bio plastic material. It is not water soluble as the starch-based types so far seen are, and it is materially stronger. Water soluble plastics cannot be used to manufacture cartridge cases due to their relative softness, low tensile strength and ability to dissolve in water. 

The bio plastic materials Bioammo has developed, and patented, do have sufficient tensile strength to make cartridge cases that will also produce a firm, tight crimp – something that even injection moulded HDPE doesn’t do very well.

Bioammo is therefore in a unique position, being able to offer shotgun cartridges with both wads and cartridge cases that are biodegradable and compostable. Bioammo supplied copies of the ‘OK Compost Industrial’ Conformity Mark, issued by the TUV Austria testing laboratories, to confirm their material’s credentials.

The inherent strength of the plastic wads should also mean that it is suitable for use with steel shot loads, including some of the heavier shot load weights which require high strength polymers to ensure full, reliable, barrel protection.

Clay loads on test

We are reviewing the lead shot, clay target load here but there are steel shot options too. The cartridges provided for testing were the Bioammo MM Rex, a 28 gram, 7.5 shot size, lead shot load.

The cartons of 25 have a striking ‘red sky at night’ look to the top and front faces, with load details on the more plain rear. Top flap and sides state ‘Biodegradable Biopolymers’ and also that these polymers are ‘of vegetal origin’.

The cases are 70mm long, light green in colour and have a 15mm high brass plated steel head. The case tubes are extruded, indicating that they are manufactured on the very successful Reifenhauser process, as are the majority of cases today.

The tubes have only the lightest of longitudinal external ribbing. This is so light that they look and feel to be smooth and shiny. The new material and, perhaps the smoothness, appears to limit how much ink the case will accept as the gold coloured printing, although very neat, is quite faint.

Bioammo components were on display at the British Shooting Show earlier this year

Inside the cases, a bio plastic base wad of similar brown colour to the wad is used to ensure case integrity with the metal head and also the full compostability of the plastic components. The metal head will rust away.

A major problem with finding suitable eco-friendly and biodegradable plastic materials to replace the HDPE plastics used in cartridge cases and wads is their physical strength properties.

Until now, the materials that are available, such as the water soluble starch based products used to make the plastic ‘Eco’ wads in Armusa, Maxam and Eley cartridges, do not possess the physical tensile strength needed for cartridge cases – plus of course a water soluble case wouldn’t work well in a damp pocket!

Bioammo cases are evidently amply strong and provide a very well formed six point star crimp closure. The fact the cases have good tensile strength is confirmed by the strong ‘memory’ the opened crimps retain in the fired cases, returning strongly to very pronounced and regular zig-zag form after firing, as do the very best HPDE plastic cases.

Shooters may have noticed that some slightly less strong cartridge cases can lose some or all of their ‘crimp memory’ but this is usually only seen with budget end cartridges. Having some idea of the important role that HDPE long chain polymers play in cartridge cases, I am, frankly, very impressed at the evident quality of these cartridge cases; this is indeed a very special polymer.

Less surprising is that, having invested millions of pounds in developing their ‘vegetal origin’ biopolymers, Bioammo has protected their creation with what they describe as “an extremely strong AAA patent in 55 countries.”

They explain “this means that we have the secure patent for the invention of all munitions with a vegetal material, and their application as a novel product that has not previously been patented, as well as their application for industrial purposes. They are also fully certificated, passing all of their tests for performance, safety and 100% non-toxic biodegradability and bio-compostability.”

This may help those currently questioning why more cartridge companies are not currently offering cartridges with eco-friendly wads. The road to such products is long and expensive.

No company is likely to invest vast financial outlay to arrive at a unique product and then give it away for others to use! There may be other similar products yet to be discovered, but the investment will be vast, the outcome uncertain and the need to avoid the Bioammo patents very clear.

The Bioammo wad

The plastic wad used is obviously also patented and uses a very similar polymer to that used for the cases. In the ammunition received for review, the wad is firm and noticeably more rigid than soluble plastic wads seen to date but is still sufficiently flexible to form an efficient gas seal upon firing.

The wad’s design follows all the established features found with HDPE wads, with a full length shot cup with four moulded slits forming four separate petals. 

he side of the box explains that the biopolymers used are of “vegetal origin” and compostable

The petals are lightly joined at the cup mouth so they feed through automatic dispensers on cartridge loading machines without becoming entangled with each other.

The moulded slots are wide and I would anticipate them being a little narrower on steel shot versions. Collecting some fired wads showed that they all opened up reliably and evenly, all petals equally open out to retard the wad’s motion once clear of the gun’s muzzle.

The biopolymer is evidently heavier than standard HDPE plastic as the weight of the wads revealed. Plastic wads of this gauge and size typically weigh between 42 and 46 grains; the bio wad weights averaged 61 grains. This is approaching 50% more material weight.

With the biopolymers much more expensive to produce than conventional plastics and more material weight required to manufacture each wad, there is clearly always going to be a quite substantial price uplift to take into account.

Powder, primer and shot

The powder is a 25.5 grain charge of Maxam PSB, a square cut flake, single-based nitrocellulose propellant. This clean burning powder gives good ballistic performance. Matched with a Maxam primer, together these produced the excellent results seen in the test reports.

The shot in these cartridges is also high grade. It is hard, as shown by the CV result, whilst well graded for even size, polished and graphite coated. The shot loads averaged 437 grains weight, one ounce, so a pellet or two more than a 28 gram load.

These are expensive cartridges and so it is good to see that the key components are all top notch too. As per our standard procedure, these cartridges were submitted to the Birmingham Proof Laboratory for pressure, velocity, momentum and consistency testing to CIP standards. Patterns were fired through a test gun with standard bore size barrel and conventional, short, forcing cones.

How do they perform?

At over 400 metres per second velocity, they are in the high velocity category and consistency is good too. Recoil is firm, a generous shot load and a heavier wad – but the shooting characteristics felt smooth, especially from a decent weight clay gun. I was surprised how well I coped with these.

The key factor that separates the budget from the premium, with any cartridge, is the quality and consistency of the patterns it produces. Weaknesses in any department result in lower pattern percentages and wider spread of pattern densities within a series.

The Bioammo MM Rex performed well on all counts. The variation between highest and lowest pattern density was among the best I have recorded with any cartridge; these components perform well together and are precision loaded.

Good quality components contributed to some exceptionally good patterns from these cartridges

The hard shot helped to produce average pattern densities just above what’s typically associated with the Imp Mod choke test barrel, at 66%, in spite of the high velocity. Well graded shot size also keeps shot strings shorter for improved results at longer range.

On Sporting clay targets they proved very efficient and were overkill for first barrel DTL, taking out second barrel shots. Using a half choke in a Fabarm S & H, I walked back from the trap until my break point was just beyond 45 yards and the Bios were still giving positive kills; with more choke and a better long range shooter, that range could be extended.

The cases and wads, when left on the ground, will take from six months to two years to be broken down by bacteria, algae and other soil organisms, to become ‘fertiliser’. The time taken will vary depending soil conditions and climate, according to Bioammo.

The materials used have been tested by independent laboratories to ensure that they are non-toxic, biodegradable and compostable. In suitable conditions, the cartridges should have a shelf life in excess of five years.

Wads will be left on the ground and soon blend in with soil. They do not dissolve in water. The base wad, being thickest, will take the longest to degrade. The metal head should rust away in a similar time. It is not clear if the polymers can be recycled.

New territory

My  concern about their success is in the willingness of clay shooters to pay the price difference for these eco-friendly cartridges, especially as clay shooters are best placed to collect their empty cartridges cases in the receptacles at shooting clubs and grounds where many are already recycled. That is my prime concern. The performance is well up to the task.

If you wish to join those following the ‘eco’ route with your shooting, Bioammo is now offering a credible option.

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