The Woodleigh Hydrostatically Stabilised Bullet

An Australian invention for world-wide use

John Marozzi is the inventor of the Hydrostatically Stabilised Bullet (HSB). The bullet started as a thought or a seed implanted in the back of his mind in the late-1970s, when John was just 17-years-old. He would listen to his Uncle Max recount stories of encounters with marauding dangerous game that raided crops and wreaked havoc in Zambia.

Initially ‘Father Max’, who had graduated from an Italian seminary, was sent to Zambia to convert the locals to Christianity. Situated near the fertile Luangwa Valley, crops were frequently raided by buffaloes. He was further exasperated by the inefficiencies of his only firearm - a Short Magazine Lee-Enfield .303 British. The factory soft point bullets proved useless on heavy muscled big game and the military full metal jackets were slow going. In one particular close confrontation with a buffalo, his .303, together with assuredly “divine assistance”, just kept him out of the potentially disastrous predicament. He lamented that if he could only find a decent bullet, his .303 would do the job.

Books on Africa by respected writers Arthur Neumann, Sir Samuel Baker, Robert Ruark, Peter Capstick, John (Pondoro) Taylor and others have touched on the significance of using a properly constructed bullet on the intended game for an instant and humane kill.

John himself grew up rabbit hunting in north-west Victoria with his father. At the legal age, he began a hunting and firearms journey that later saw him progress to large calibre rifles for pursuing big game in the Top End and overseas.

When he reached the time to choose a career path, he was encouraged and spurred on by a close friend and hunter, who had the foresight to see where particular industries like mining were headed, to take up metallurgy. John’s connection with hunting, paired with his interest in science, geology and metals, along with the role potentially taking him into outback places like Broken Hill and the Kimberley, helped his decision.

In 1983 John graduated with a Bachelor of Science in Metallurgical Engineering and started employment in 1984 as a graduate metallurgist with Extruded Metals in Maribyrnong, Victoria, from there quickly advancing to factory manager. Here one day while in the state-of-the-art tool room appreciating the workings of a machine that manufactured hollow brass rods by using a piercing mandrel in a 3000-tonne extrusion press, the creation of a better bullet utilising the extrusion process before him began to gel. The procedure of developing the idea into reality began.

Idea becomes reality

Extreme compression forces the mandrel to self-centre. The hydrostatic forces created by the mandrel nose design as it passes through the bullet form a concentric hollow bar. Therefore, it occurred to John that a bullet was essentially a floating tool under extreme compressive forces. By using the concept of hydrostatic stabilisation, he believed he could design a bullet which would track straight, penetrate deeply and create a wound channel superior to existing products on the market.

Initial tests started with .375 Cal 300gn flat-tipped solids turned at home on a small lathe from standard machine brass for his .378 Weatherby. However, pressures were elevated and when they hit heavy bone the bullets broke in half. A better material was required. It took a further two years and trialling some 20 grades of copper zinc alloy to achieve the end product used today - a bullet that exerts similar pressures to standard bullets, which is tough enough to withstand high impact but was mild on rifle barrels. It took several more years of testing various prototypes before settling on the final design.

Using his scientific knowledge and thinking analytically, John deduced that once a bullet had fully mushroomed, much of the energy was absorbed in expanding the bullet. He was motivated by the belief that if the nose was designed so that it didn’t distort or expand, there would be more energy directed towards creating a large wound channel. This was finally achieved by forming a depressed cavity in the tip of the bullet, combined with a negative ogive shoulder, which in flight became surrounded by a stabilising air pocket to resist deflection.

Throughout challenging testing and field trials, John’s strong will to succeed prevailed to produce a unique bullet that would deliver vastly improved performance compared to standard solid bullets. The bullet was extensively tested in the field and on various mediums, including ballistic wax, focusing on the extent of bullet penetration and cavitation. Valuable feedback on testing and bullet recovery was provided by Dave Lindner, of the NT, an expert on firearms and field ballistics since the 1960s and a true conservationist. As a ranger in the 70s Dave spent the greater part of his life culling feral animals like the destructive Asiatic water buffalo and wild pigs for the authorities, while protecting the habitat in and around Kakadu for the Traditional Owners and touring visitors.

Graeme Wright, a firearms expert and noted author of Shooting the British Double, tested for deflection. Mark Patterson, of Katherine, conducted numerous field tests, particularly with doubles, resulting in small but important design changes, and Geoff McDonald, founder and owner of Woodleigh Bullets, was also instrumental in its testing at various levels. Abroad, Clive Conolly, renowned big game hunter and Olympic representative shooter for Zimbabwe, extensively tested the HSB on dangerous game in Africa. Together with the assistance of other friends in Australia and Africa, the HSB was comprehensively assessed.

Today we now have a bullet that rivals its competitors and bridges the gap between modern solids and expanding bullets. It is used by Personal Hunters locally and overseas, guides, hunters and shooters. In my own testing of Woodleigh HSB in my Winchester Mod 70 Safari .375 H&H at the shooting range, I was surprised at the results. Shooting at a paper target in front of a 12” thick seasoned redgum log at a distance of 100m, the Woodleigh HSB performed accurately and lodged deep and actually maintained its integrity and seemingly unaltered form. In the field trials, similar recoveries were experienced.

From my perspective, I regard the Woodleigh HSB as a uniquely superior solid bullet. It is generally accepted as the seventh generation in consumer bullets. First: round lead ball. Second: hard lead slug. Third: jacketed lead core. Fourth: tapered jacket lead core-controlled expansion. Fifth: bonded core-controlled expansion. Sixth: homogeneous. Seventh: hydrostatically stabilised. This Aussie invention is the only bullet that combines all these features and as such has world-wide IP protection to ensure it continues to be made here in Australia.

Overseas recognition and accolade

In July 2013, Federal Premium Safari Line ammunition loaded with the Woodleigh Hydrostatically Stabilised Bullets won the prestigious Field & Stream Best of the Best Award in the US.

Here is part of the media release which is highly complimentary of the HSB:

“Federal Premium Ammunition is proud to announce its new Safari Woodleigh Hydro Solids have won a coveted Field & Stream 2013 Best of the Best Award. The loads were singled out because they feature the most advanced technology and the consistent performance required for once-in-a-lifetime shots in life or death situations.

“The winning products not only withstood our tough testing, but they stood head and shoulders above the rest, displaying absolute excellence in their field,” said Slaton White, Deputy Editor of Field & Stream.

“The Best of the Best is the highest honour Field & Steam bestows on gear… worth your time, worth your money.”

 “The Hydro Solid is built to give perfect straight-line penetration,” said David E. Petzal, Field & Stream Field Editor. “Tester John Blauvelt and I shot the Hydro Solids in 9.3x62 Mauser, the metric equivalent of the .375 H&H. They went through everything we could put in front of them. Everything.”

Mike Holm, Federal Premium’s Product Manager, said hunters have long relied on solid, non-expanding bullets that blow through bone and thick hide when targeting the largest and most dangerous game.

“The new Woodleigh Hydro Solid offers that same unstoppable penetration while also creating a massive wound channel and large entry cavity that won’t seal,” said Holm.

Technology and performance

The new Woodleigh Hydro Solid offers the unstoppable penetration of a solid, non-expanding projectile while also creating a devastating wound channel and large entry hole that won’t close. The solid copper-alloy bullet uses an advanced design with a concave nose positioned ahead of a flared pressure ring.

Combined, these attributes create a low-pressure “cavitation bubble” that destroys tissue around the bullet and stabilise its line of travel through heavy bone. A special polymer cap protects and stabilises the bullet until impact. The nose cap also ensures reliable cycling. The bullet features a grooved shank for match-grade accuracy and is loaded in a Federal Premium nickel-plated case for reliable, easy extraction.

Calibre range for the HSB

Since its initial appearance, further calibres have been added to the list to meet demand. Today the Woodleigh HSB is available in a wide range of rifle calibres from medium calibres: .7mm, .308, .303, .338, .358, 9.3 and .375 to larger calibres: .450/400 3”, .416, .404 Jeffrey, .450, .45/70, .458, .465, .470, .500, .50 Alaskan, .505 and .577.

In line with good practices and where magazine rifles are involved, it is recommended ammunition loaded with HSB bullets be cycled prior to firing, adjusting seating depth as necessary to ensure proper chambering.

Suitability for lesser calibre rifles

The Hydro allows game to be taken with calibres that may normally be considered under-powered. For those of us who are sensitive to recoil, this is very important as it should help with more precise shot placement. Many women have successfully taken buffaloes and scrub bulls in Australia’s Top End with lighter calibre rifles such as the .308 Win or .30-60 Springfield, using 180gn and higher hydrostats. In the NT, feral camel and donkey culls have been undertaken humanely by landowners and professional hunters using similar calibre rifles and ammo.

Potential target game

Australia: thick skinned wild boars, bulky sambar deer and red deer, scrub bulls, feral camels and donkeys, and Asiatic water buffaloes. Africa: Cape buffaloes, wildebeests, elands, kudus, oryxes, sables and other similarly built hardy game ‑ bearing in mind when on a safari hunt you must pay for any lost or unrecovered wounded animal. America, Canada and British Columbia: moose, elks, caribou and other deer species and large game. Similarly, with other parts of the world and game.

Our own invention

The Hydrostatically Stabilised Bullet is simple in design and appearance yet complex in its structure and composition. It was developed in Australia in collaboration with Hargo Engineering owner Frank Gogol, whose cutting-edge repetition engineering company was instrumental in the development of the acetal bullet tip and the bullet’s overall production. In addition, Geoff McDonald, of Woodleigh Bullets, a keen hunter and bullet/ballistic expert, was involved for its extensive testing and marketing, along with individuals and entities.

Those who have used the Woodleigh HSB in their hunts and others who have acquired the Woodleigh Bullets Loading Manual would be aware of its existence and potential. However, judging from feedback received from various gun dealers and shops, and interaction with shooters in general over a period of months, its presence is still not widely known.

Key features

●Can be loaded similarly to a round-nose, soft-nose (RNSN) projectile without dropping black powder grain.

●Makes less contact with the walls of the bore due to its bore rider design with driving bands, resulting in reduced pressures and a longer barrel life.

●Resists deflection through heavy brush and bone.

●Hydrostat leaves a permanent open cavity or channel.

●Exceptional penetration through tough muscle, tissue and bone structure.

●Acetal tip survives recoil and friction pressures but disintegrates completely on impact, which prevents a feeding problem into the rifle and improves the ballistic coefficient.

●Composition makes it very tough, accurate and environmentally safe.

Subscribe to Australia’s favourite hunting magazine here: https://membership.ssaa.org.au/forms/hunter

National E-newsletter

The SSAA National E-newsletter is a subscription email service available FREE of charge to SSAA members. It includes current and upcoming news, views and events about firearms ownership, sport shooting and recreational hunting issues, important SSAA news, special offers and time-sensitive news.

Facebook Feed

National Membership

[email protected]

+61 (0) 2 8805 3900

PO Box 282, Plumpton NSW 2761