Mary Arm Sport cartridge test w/ Richard Atkins

Richard Atkins is back with a Mary Arm Sport cartridge review, as he puts two of the budget cartridges to the test

A new name is being heard and seen on the clay target scene: Mary Arm. Their cartridges have appeared in the UK before but somewhat sporadically, and it’s a while since I last saw them.

That changed recently with a call from Mike Bartlett. Many will recognise Mike as not only a serious and successful Sporting clays competitor but also the man who designed and manufactures the Magic Bore shotgun cleaning system.

Anyone with one of these will be aware of Mike’s attention to detail and insistence on quality. It is reassuring to know that Mike has applied his desire for quality in seeking out the Mary Arm cartridge range to promote in the UK. Not only is Mike a keen and talented shot but his partner, Cheryl Hall, is a champion shot in her own right.

Cheryl is one of the UK’s most successful sporting clays shooters; we can be sure that these Mary Arm cartridges have been closely examined and tested by two people who really know what it takes to make big scores on serious competition layouts.

Mary Arm cartridges are made in Bergerac, France, founded 65 years ago by Jacques Mary. The company built its reputation on innovation and ballistic performance along with quality and rigour of loading. This excellence has been upheld by Jacques’ son, Pierre Mary, who is also passionate about hunting and Ball-Trap, and has continued to develop the brand’s success in France and internationally.

Among their extensive credentials, Mary Arm are used by winners of national, European and world championships. This tells us that Mary Arm clearly do know how to manufacture top grade cartridges.

Naturally, all the premium cartridges sought by serious competitors come with a larger price tag and, with many shooters having to tighten their belts at this time, Mike has also sought to bring some of the competitively priced end of the Mary Arms clay cartridge range here.

We take a close look at two of them this month: the Sport 28 SCUD, one of the most competitively priced 28 gram plastic wad loads around at a SRP of £180 per 1,000; and the CYRANO, a keenly priced BIOR wad cartridge at £202 per 1,000.

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 when subjected to the 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 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%.

Mary Arm Sport 28 SCUD 28 Gram 7.5 Shot Plastic Wad

Sport 28 SCUD has been developed to offer an economically priced cartridge capable of producing a performance level above what you might expect for the money – a very competitive sector of the current UK clay target market.

The shells are smartly presented in sturdy cardboard cartons of 25, with the top flap showing basic cartridge description of gauge, shot weight and size. With a clay shooter depicted large on the front, the Sport 28 certainly look the part.

Cartridge cases are light blue Cheddite, 70mm long, parallel plastic tubes with an 8mm brass plated steel head. Primers are the excellent CX2000 which are known for their reliable ignition and consistent performance. Primer flash holes are sealed with Cheddite’s characteristic lacquer coating that keeps the priming compound in perfect condition and also prevents ingress of propellant.

Propellant is the excellent French made Vectan type D20SE. This is a green, single base disc propellant, another top quality component. It burns very cleanly and produces consistent ballistics at moderate charge weights with an average 23.5 grains achieving a quick cartridge with a V2.5 velocity only a shade under 400 m/s.

The plastic wad carries the designation JM24BJ, specially produced for Mary Arm. Close inspection reveals it to be well moulded with a precise centre section. This is designed to support the shot column well and progressively compress upon ignition for good shot crush prevention, combined with a good gas sealing base.

The shot cup features the usual four moulded petals; these are held closed for loading by thin plastic strands which are designed to open up quickly on emergence from the muzzle. The wad design results in a wad that is lighter than average for a 12 gauge 28 gram capacity wad.

Less weight helps keep both cost and recoil down, as everything that leaves the barrel counts as ejecta for momentum calculations. Examining fired wads showed that the wad performs well, with the gas seal proving efficient; the shot cups also open up reliably to ensure the wad falls away from the shot pellets on leaving the muzzle.

The all-important shot

The shot load is always critical to the overall performance of any cartridge. However good the rest of the components may be, if the shot is poor then best performance will be constrained.

Being the single most expensive component in a cartridge the shot is where the greatest saving in production costs can be made and that is why shot quality is a key factor in knowing the true grade of any cartridge.

The hardness of the shot used will largely determine the maximum pattern density that can be achieved. Higher antimony shot is more expensive however, so this poses a difficult balancing act on the part of cartridge makers and particularly so in the ‘budget’ market. The crush value result for the SCUD shot puts it in the mid range of antimony content and therefore in the middle of the hardness scale. 

As you can see in the components photograph, the shot pellets have a pleasing shiny black surface finish, having been well polished in graphite. Pellets have been quite well graded for size too, the majority being within a range of 0.006in diameter. The stated shot size is 7.5, with the “2.40 Ø” indicating that this is the French size which equates to UK shot size 7.

Tests and performance

The Sport 28 cartridges were submitted to the Birmingham CIP Proof Laboratory for pressure, velocity and momentum testing. Pattern tests were conducted at 40 yards from a 30in long, standard bore size barrel with 2¾ in (70mm) chamber with standard length (short) forcing cone and bored Imp Mod (UK ¾) choke.

They produced uniformly good results! Considering the high velocity, the 60% average pattern result is good and equates to half choke, so 5% more open than the test barrel’s nominal capability: similar budget cartridge types have only just exceeded quarter choke pattern density.

Faster cartridges produce more momentum than slower ones with the same payload. I was pleased to note that I was able to shoot these comfortably enough in my clay guns.

First barrel DTL and the closer to mid-range Sporting targets were all dealt with well. Mike Bartlett tried them out on a Sportrap layout and filled in a 25 ex-25 first time out, demonstrating that they will cope with trickier birds.

You can detect the extra ‘smash’ that a decent premium grade, premium price cartridge can produce, but there’s no doubting that the Sport 28 can cope with the majority of targets encountered on a typical recreational Sporting layout, as well as DTL targets and the like.

I was pleasantly surprised by the SCUD; at their current price they are well worth giving a try. Use the saving to buy a box or two of premium loads – Mary Arm offer the ‘M’ and ‘F’ Competition range too for the more distant and demanding targets.

Mary Arm Cyrano 28 Gram 8.5 Shot Bior Wad

The Cyrano 28 cartridge is presented as Mary Arm’s best priced cartridge with the Bior plastic wad. This wad differs from the conventional plastic cup wad in that it does not have a full length shot cup and instead features two quite substantial, deeper than usual gas seal cups, one at either end.

The Bior wad used is the Italian BR 12/21 by leading plastic wad maker Gualandi. It features Gualandi’s trade mark oval form central section with additional cushioning tubes and stabilising discs. The external surfaces of the cups at each end are heavily serrated, to reduce barrel friction and allow trapped air to escape past the wad during high speed loading.

The Bior wad weighs in at 43.5 grains, around the same as a typical full cup plastic wad, thanks to its robust construction. Gualandi could, no doubt, have made it lighter but weight may play a role in this wad’s purpose; that being to produce slightly wider patterns at closer range. The short cups ensure that most of the shot load will come into contact with the barrel walls where some pellet abrasion will occur.

I think it likely that the wad’s weight, combined with the lack of shot cup petals to retard forward travel, produces a short period when the Bior wad is pushing the rear of the shot column with a tendency to spread the shot column slightly outward.

As for the name, Bior, this is an abbreviation for the wad’s format. In the Gualandi catalogue it is described as ‘Borra Biorientabile’ which translates to “Wad Bi-orientable” and essentially tells us that this wad is reversible and can be loaded into the cartridge either way up. This makes life much easier for manufacturers as there is no need to ensure that all wads are the ‘correct’ way up when inserted into the cartridge case.

The one caveat I must mention with regard to the Gualandi Bior wad, in any make of cartridge, is about their use in guns with much lengthened forcing cones, which results in a much enlarged bore size in the front portion of the barrel bore.

Heavy fouling, a combination of plastic and lead, has been reported in a proportion of guns of this type. Work is ongoing as to why some guns of this type appear to suffer this more than others. The only way to be sure is try them in your gun and see how you get on. In the vast majority of guns this issue will not arise.

Powder and shot

The shot in the CYRANO ammunition tested proved to be round, well polished with graphite giving a glossy black finish and quite consistent in size. Aside from a low number of smaller pellets, the vast bulk had barely 0.005in variation in diameter. 

The hardness test results showed that the shot had a moderate amount of antimony content and gave a 33 per cent crush value. Given that these cartridges are intended for a shorter range uses, this shot is quite hard and the size consistency surprisingly tight.

Actual shot size proved interesting. The marked size is 8.5 (2.1mm); a shot count per ounce of around 500 pellets. Pellet count actually averaged 400/oz which is precisely UK size 7.5 with average diameter 0.089in (2.26mm): the larger size accounts for the lower pellet count. 

The 70mm plastic cartridge cases, primers and propellant powder are the same quality used in the Sport 28 SCUD. CYRANO cases are white and the brass plated steel head is 12mm high. Cases are neatly closed with a six point crimp closure.

The slightly smaller charge weight of 22.6 grains of Vectan D20SE propellant gave a surprisingly brisk velocity of 403m/s with a modest breech pressure of 554 bar, comfortably under the CIP 740 bar limit, according to the French ballistic laboratory.

Tests and performance

The CYRANO cartridges were a late addition to this review which meant there was insufficient time to obtain proof reports from the Birmingham laboratory. The ballistic figures given here were provided by the Mary Arm Laboratory, which works to CIP standards. 

The laboratory report reveals are very respectable set of results with a velocity level above the ‘magic’ figure of 400m/s. That is seriously quick; fortunately the recoil I felt in the restricted time available for me to shoot these particular cartridges did not reflect this and I found the CYRANO quite comfortable to shoot.

The shot size in this sample proved larger than 8.5, meaning fewer pellets in the shot load, but the relatively hard shot helped put a higher percentage (62-60%) in the 30in pattern circle. With more pellets in the inner 20 and outer 20 to 30 zone at 40 yards there is obviously better pellet density for very effective patterns. 

For closer targets, which BIOR cartridges are usually used for, opening up the chokes could be a good idea too. I would have like more time with the BIOR but the results here speak for themselves.

In summary

Mary Arm’s SCUD and CYRANO are two new cartridges for UK shooters to
try out and see how they work for them. Results here show that both of them offer competent performance.

They are currently being offered at £202 per 1,000 for the CYRANO and £180 per 1,000 for the Sport 28, making them very competitively priced – best try some while they are at these prices! 

More cartridge tests from Richard Atkins

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• Target load review w/ Richard Atkins
• Caesar Guerini’s Invictus VII Sporter – Richard Atkins review
• Browning B525 SL review w/ Richard Atkins
• Richard Atkins tests the ATA Supersport Adjustable