Index linked

Recently, I was invited to an engineering firm that’s little-known in airgun circles – though it is well-known in the world of high-performance car parts and military ballistics. The airgun arm of this company is called Pneumatic Ballistics – and my welcoming host was James Lawson.

005_Pneumatic Ballistics_James Lawson

Like so many airgun engineers, James started his involvement with airguns as a young lad. Eventually he got a BSA Super-Ten – the Birmingham gunmaker’s first precharged pneumatic – but as good as that PCP was, James found himself constantly frustrated by the magazine. “It kept jamming and not properly indexing,” he says. “It drove me up the wall, because it was a magic rifle with a real Achilles heel, that could so easily have been resolved from the outset.”

Well, he would say that – because James was brought up in an engineering environment. His father was a successful engineer and designer, responsible for the design of the two-stroke power valve used by Yamaha, amongst other things – and his expertise have clearly rubbed off on James. As James could so easily decipher the flaws in the BSA’s magazine design, he set about solving the problem… by making his own replacement magazine in his father’s workshop.

001_Pneumatic BallisticsThe fix for the problem was so simple that both father and son wondered why the factory hadn’t done it themselves from the outset. The secret of James’ design was that it did away with the mechanical indexing system altogether. “It was the most logical answer, to me,” he divulged. “My solution was to use a spring-loaded pellet drum that automatically rotated to the next position, using the pellet itself as the register point. That would ensure the pellet, magazine chamber and breech would always be perfectly aligned.”

The first magazine he made for his own SuperTen incorporated a nine-shot drum, rather than the 10-shot system of the original BSA design. “I had to ‘lose’ a shot,” he explained, “because of the thickness of the stop post I used.” Once James had seen how well his new aluminium-made magazine held up in use, however, he decided it was possible to reduce the size of the end stop without compromising the strength or longevity of ‘his’ magazine design. “Consequently,” he said with a smile, “I was able to modify my system to make room for that tenth pellet. It would have been a bit silly to have only nine shots – the gun was, after all, called a Super-Ten.”

Ultimately, having undertaken plenty of hours of field tests, the Lawsons took their design to BSA themselves. “They were impressed,” said James, “and even asked my Dad’s company, Pneumatic Ballistics, to make the magazines for them.

004_Pneumatic Ballistics

“However, they also wanted the BSA logo machining onto each magazine, rather than our ‘PB’ logo. Ultimately, that became a sticking point and we were unable to agree terms to put our concept into factory production.” However, James did suggest to me that the design of BSA’s latest magazine – as seen on the SE models and MkII R10 – follows his concept so closely that “the internal parts are interchangeable.”

As well as hours on the static test-bed of an engineering workshop environment, James’ field-testing also spanned his own hunting forays. “I shoot dozens of rabbits and hundreds of rats every year,” he told me, “so I wanted something more than just a reliable magazine system.”

When engineers start wanting ‘something more’, it usually means their mind is running away – and in James’ case it was no different. He had the idea of grafting two magazines together in order to give him double the amount of firepower in the field. “I thought it couldn’t be too difficult,” he explained. “It would simply be a case of doubling up and turning the magazine around. I actually got the idea while watching Vietnam war movies, where the GIs used to tape two magazines together for their M16 assault rifles.”

003_Pneumatic BallisticsHe started ‘experimenting’, and soon found that the ability to have 20 shots pre-loaded in the rifle is so much easier in the dark than changing magazines. “It was ideal for those pest control operations where a high number of shots are required in a short space of time,” he commented, “like clearing feral pigeons and rats. For me, they’re always the fastest, most furious of forays.”

However, as a project, the concept proved more difficult than merely doubling up the dimensions of the magazine. James explained: “I wanted to make the double-10 magazine system as compact as possible, but it was a challenge to ensure accurate alignment from both ends without making the end-product too bulky.”

However, an engineer’s work is never done until it is done, and James finally achieved an end-product – not just to suit the BSA SuperTen, but also other rifles. Pneumatic Ballistics now has retro-fit, double-capacity magazines for Air Arms’ S410 and S510 range, BSA’s PCPs, Daystates and the Theoben Rapid series in .177, .20 and .22. They are available in black- 026- anodised aluminium, although some are shown ‘in the white’ here.

201 Daystate PB mag

In all cases, the mechanical indexing system is redundant – the magazines are completely self-sufficient. What’s more, these bespoke items are true custom parts, and James has gone out of his way to engineer something that looks, feels and operates like the high-precision component that these magazine works of art actually are. “The ability to use state-of-the-art computer-aided design (CAD) and modelling helped enormously,” he admitted. “It meant we could ensure complete accuracy before we even began the machining process.”

Pneumatic Ballistics’ magazines are made on CNC (computer-number-controlled) machinery to extremely tight tolerances, with the aluminium case reinforced by male and female locating lugs that effectively create pillar supports within the case at each drum axis point. This ensures everything remains perfectly aligned and cannot go out of shape… “even if dropped end-on onto a concrete floor,” assured James.

100 SMK PB CO2 chamber conversionThe pellet drum has a knurled edge so it can be loaded with ease, even with cold or wet fingers, and the pellet chambers are each bevelled to make dropping a pellet into place as fuss-free as possible. “I wanted to put an end to fiddly magazine loading,” said James.

Unlike many mass-produced magazine systems, there’s no rubber O-ring in the PB unit. “These eventually go hard and perish,” James pointed out, “but they’re simply not necessary in my design.”

Another feature of the Pneumatic Ballistics design is the end ‘stop’. Instead of the magazine’s last shot finishing with a pellet chamber, the PB system is engineered to rotate just a little further after the last index. I asked James why he’d done this: “It’s so that you don’t waste any air firing a ‘blank’ after you’ve emptied the magazine,” he said. “Most airgunners lose track of their shots, and this prevents you indexing to an empty chamber after your true last shot.” There are coloured indicators to give a visual guide as to the magazine’s status but, as James explained, they’re not always so easy to see: “When night-shooting, for instance.” Custom-engineered parts are never cheap, but the PB retro-fit magazines are very price-competitive when compared against the cost of two originals – and their quality has to be seen in the flesh to be believed.

204 PB mag - Theoben Rapid

Of course, James’ original design came about because he wanted better reliability – so that can’t really be called into question, either. For airgunners who shoot the Theoben Rapid series of PCPs, there’s also another benefit. “A drawbacks with Theoben’s high-capacity mags is that they only load from the left,” James demonstrated to me. “This makes the use of a scope wheel nigh-on impossible and certainly impractical – so I’ve designed my Rapid version to load from the right.”

CO2 TO AIR CONVERSIONS

Interestingly, it isn’t just magazines for top-end PCP air rifles that Pneumatic Ballistics is becoming known for. The company also does air conversions for SMK’s CO2-powered air rifles.

For those which take the 12-gram capsules within a chamber, James has designed a filler valve conversion that replaces the end cap. “It simply screws on the end, allowing the rifle to be filled with compressed air from a bottle or pump,” explained James, although he added the caveat that undertaking such a conversion will invalidate SMK’s warranty. James has ‘pressure tested’ these rifles’ air chambers, and confidently claims a safe, maximum working pressure of 150BAR.

For the larger, 88-gram CO2-powered SMK air rifles, Pneumatic Ballistics also offers a buddy-bottle replacement for the CO2 tank, also tested to a SWP of 150BAR. “As the throw-away CO2 canisters are quite expensive, many shooters are turning to this air conversion to save costs in the long-run,” James said.

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Posted in Behind the Scenes, Features
One comment on “Index linked
  1. michael neal says:

    reading about your co2 to air conversions for smk air rifles my model is th78d do you do one to fit if so how much is it.no costs are on your web pages. thank you mike

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