50 Years Of Bullet Design Improvements
January 04, 2011
Innovative characteristics seen on today's big-game bullets include boattails, ballistic tips, and bonded cores.
All of you can generally describe a bullet's purpose: It projects the shooter's intent. Whether you're hunting (beast, bird, or man), defending yourself or someone else, or simply punching holes in paper, the bullet simply transmits the message you intend to convey.
Bullet design has progressed dramatically over the last 50 years, which is the topic of this anniversary issue's column.
Good design complies with the engineering tenet "form follows function," i.e., specific requirements translate into a unique design. Physical and system constraints limit design options, e.g., certain materials make the "best" bullets, and projectiles must be "spin-stabilized" by the rifling to be accurate. And, of course, as the designer strives to achieve optimum ballistic performance, the bullet's shape and construction must comply with the rigid laws of physics.
Because the bullet's ballistic performance is primarily related to its physical characteristics, the jackets must be absolutely concentric and exhibit no dimensional variations. Material properties and fabrication processes must not deviate so that every lead core weighs the same and the nose and base shapes and shank diameters are identical. For 50 years, the manufacturers have continuously strived to make their products as precise as possible.
However, the myriad design solutions to achieve other desired performance objectives have often varied significantly. For example, a varmint bullet's external and terminal ballistics requirements are simple (theoretically); they should travel 500+ yards in a straight line and explode immediately upon impact.
Speer's TNT and Hornady's SX bullets have thin jackets and soft lead cores. The TNT has a hollow point to ensure violent expansion. The Barnes Varmint Grenade also has a thin jacket, but the core is a compressed mixture of iron and polymer particles. The Hornady V-Max, Sierra BlitzKing, and Nosler Ballistic Tip bullets also feature polymer tips and boattail bases to maximize the bullet's ballistic coefficient, i.e., provide the flattest possible trajectory.
Target bullets have a primary performance objective--accuracy--so bullet makers are less concerned about how to design a better bullet and instead focus on improving manufacturing processes. Independent bullet makers like Berger and Shilen are familiar names on the benchrest circuit. Sierra Match-Kings have historically claimed top product for extended-range competition; however, Hornady's A-Max recently mounted a challenge to their dominance.
In the arena of hunting bullets, nearly everyone continues to try to develop better mousetraps. Today's buzzwords describing optimum bullet performance include maximum penetration, controlled expansion, and weight retention. The most recent popular products include bonded bullets and ones that are completely or at least partially "lead-free." But let me recap the earlier improvements first.
In the early 1960s, Hornady switched to a secant ogive nose shape to improve ballistic coefficient (BC), i.e., flatter trajectory. Then the company began to score the jacket internally to ensure positive and consistent expansion. Soon after, Hornady added an internal ring in the jacket to "interlock" it and the core to avoid separation after impact.
Hornady recently introduced Flex Tip bullets. Initially, they were rifle bullets for lever-action cartridges. They feature pointed ballistic tips made from a soft polymer so they can be safely used in tubular magazines. However, the tips also aid expansion, and Hornady soon offered handgun hunting and personal-defense bullets with this technology.
Speer introduced the Hot-Cor bullet with a flat base and tapered jacket in the early 1960s. Instead of inserting a cold-swaged lead core, molten alloy is injected into the jacket to ensure no air pockets or contamination form between the core and jacket that could cause instability in flight or core separation. The Mag-Tip is also a Hot-Cor design with a more streamlined nose profile and thicker jacket. Speer makes the popular Fusion bullet for ammo marketed by Federal Cartridge. Both Fusion and another new series of Speer game bullets will be offered as reloading components this year.
Sierra has made the fewest changes to its original design mantra--accuracy. MatchKing bullets hold seven places on the latest top-10 selling SKUs list. The GameKing product line, although it has evolved over the years to improve terminal performance, still adheres to the firm's focus on accuracy. They may have a hollow point or a lead tip. Jacket thickness and core alloy (i.e., hardness) will vary depending on the caliber and intended quarry. Most have a boattail to maximize flight performance. And they still kill game reliably. Plastic tips are only found on some of the BlitzKing varmint bullets.
Nosler introduced the Solid Base bullet (sans partition), and it was soon followed by the ever-popular Ballistic Tip. Both feature a tapered jacket and massive, boattailed base with a plastic cone added to the nose of the Ballistic Tip. Hornady's SST design was derived by adding a plastic tip and boattail to the Interlock design, and Remington's AccuTip bullets share similar features.
Non-Traditional Hunting Bullets
In a bonded bullet the internal core is chemically or thermally joined with the jacket. Contrary to what you may believe, bonded bullets have been around at least since the late 1940s. P.O. Ackley experimented with them about the same time John Nosler was developing his Partition bullet.
Bill Steiger introduced Bitterroot Bonded bullets in the late 1960s. Jack Carter marketed Trophy Bonded bullets soon after. The Swift A-Frame, introduced in 1984, is similar to the Nosler Partition; however, the jacket is pure copper and the forward lead core is bonded. Nosler added the AccuBond to its product line a few years ago, and it shares the basic Ballistic Tip design, but the jacket and base are much thicker and the core is thermally bonded to the jacket. The Hornady InterBond, Remington Ultra Core-Lokt, and Swift Scirocco II have similar designs (plastic tips and boattails) and construction features.
In 1989 Barnes introduced the X-Bullet, which is a pure copper bullet with a skived, hollowpoint nose. The idea was to provide controlled expansion and deep, straight penetration. Most of the time, the nose petals peeled back and remained attached as advertised, resulting in spectacular terminal ballistics.
Copper is less dense than lead, so the X-Bullet's overall length was greater than a traditional jacketed, lead-core
bullet of equal weight. So in order to not exceed maximum cartridge overall length (COL), the bullet had to be seated deeper. Likewise, shank length exceeded the typical bearing surface, and pure copper is more "sticky" than gilding metal. Both factors caused increased friction, i.e., more pressure. Understandably, handload recipes for comparable caliber/weight X-Bullets were significantly different.
Barnes XLC bullets featured a coating to negate these issues. However, a few years ago Barnes improved the original X-Bullet design and introduced the Triple-Shock (TSX) with a more pronounced boattail and multiple grooves spaced along the shank to reduce friction. This change was soon followed by the Maximum Range (MRX) bullet with a tungsten (heavier than lead) core to reduce overall length. Most recently, Barnes has added the Tipped TSX and the Multi-Purpose Green (MPG) to its ever-expanding lead-free product lines. Barnes still offers a few of the original copper-tubing-and-lead-core bullets for some of the old lever-action cartridges.
Other bullet makers offer similar bullets. The Nosler E-Tip and Hornady GMX have polymer tips and are made of copper alloys instead of pure copper. The GMX also has a grooved shank to reduce friction. Nosler has recently introduced a Ballistic Tip lead-free varmint bullet with a frangible-powder metal core that looks and performs like the regular "leaded" varmint Ballistic Tip bullets.
Then there are the bullets that combine a partial lead core with a copper or copper-alloy body. Trophy Bonded Bear Claw bullets have the lead core in the nose and were marketed by Speer. This year, they acquired multiple grooves, nickel plating, and a plastic tip and are branded as Federal's first component bullet. Winchester's XP3 design reverses the Trophy Bonded Bear Claw's arrangement, i.e., the lead core is in an aft cavity. Federal will also offer the Sledgehammer Solid (FMJ-FN with lead core, not plated) for straight and deep penetration in dangerous game animals that can bite back.
Just one, final comment and that's about enough--or I will surely have overstepped into the book writing realm. Today's shooters and hunters have literally hundreds of bullets to choose from, and the bullet makers are constantly developing even more to meet customers' desires. So have fun loading and shooting them!