Strolling down the ammunition aisle at your local gun shop will reveal a multitude of different brands, loaded with a near-dizzying variation of projectiles. It can be downright confusing, especially if you are unfamiliar with the various construction methods and their applications.
The simple round lead ball, used as the projectile of choice for centuries, slowly morphed into the more common, elongated design we're all familiar with. Almost as a parallel development — and largely because the lead bullets couldn't handle the increased velocity — smokeless powder and the jacketed bullet came on the scene at the latter part of the 19th century. This was an absolute game-changer. The idea was simple and genius at the same time: a jacket of copper — harder than lead, but soft enough to engage the rifling properly — surrounds a core a lead. Fouling (leading) of the barrel was greatly reduced, and the expansion of the bullet upon impact with a game animal was slowed a bit, giving good penetration. It is this design — the cup-and-core bullet — that originated in the 1880s, and remains with us to this day.
Many of the most popular bullets — the Remington Core-Lokt, the Hornady InterLock, the Sierra GameKing, Nosler Ballistic Tip and Winchester Power Point — are constructed in this manner, and have served us well for decades. That's not to say that they don't have their own set of shortcomings; as the velocities increase, and/or if the bullet has a low Sectional Density value, jacket-core separation becomes a challenge. But, if of appropriate weight for caliber, they are a good choice for general hunting.
John Nosler learned that lesson the hard way; he had cup-and-core bullets loaded in his .300 Holland & Holland, and as he was hunting moose in the 1940s, he saw that his bullets were failing. They simply couldn't handle the strain of high impact velocities on a moose's shoulder and had expanded rather prematurely, and he set out to build a bullet that wouldn't let him down.
In order to prevent premature expansion, Nosler decided he'd use two lead cores, separated by a partition of copper jacket; the Nosler partition was born, and along with it the premium bullet market. It's a flat-base spitzer design, and brother, it works. Though it turns 70 years old this year, the design is, was and will be a winner in the field, suitable for nearly any game animal for which an expanding bullet is suitable.
There were several other historical attempts at achieving that perfect balance of expansion and penetration. The Winchester Silver Tip (the original under that name) used a hard, alloy cap over the exposed lead nose to slow expansion and guarantee penetration. The Speer Grand Slam used lead cores of differing hardness in order to hold things together. Bullet companies produced projectiles with thick jackets; the amount of exposed lead at the bullet's nose was increased and decreased. But the next major innovation came from a removal of one component.
Mr. Randy Brooks — then owner of Barnes Bullets — was sitting and glassing for brown bears in Alaska, when he had the genius idea of removing the lead core entirely. A bullet comprised entirely of copper was a radical idea, and it came with its own set of complications. I did not have good luck with the original Barnes X, but I can certainly report better results, both in accuracy and terminal performance, with the TSX and TTSX.
Being all copper, a bullet of a particular weight will be longer than the same bullet that uses a lead core, and the center of gravity does in fact shift a bit rearward, but one thing is for sure, they hold together and penetrate deep, retaining a good percentage of their weight. Barnes ushered in the monometal expanding bullet, and it's a sub-market that is thriving to this day. The Federal Trophy Copper, the Hornady GMX, the Nosler E-Tip, The Cutting Edge Raptor, the Norma Eco Strike and the Peregrine BushMaster are all examples of good monometal bullets. Lead-free ammunition is required by law in California, and by choice elsewhere, and I guarantee the design is here to stay.
Meanwhile, engineers continued to work to perfect the cup-and-core bullet. The separation problem was solved by bonding the lead core to the copper jacket, either by soldering the two, or using a chemical for the bonding process. This definitely slows down the expansion process, and helps the bullet to retain its weight after impact. Early on, Bitterroot Bullets brought this process to the forefront, but it has most certainly caught on.
The Swift A-Frame (a modern version of the Partition) has its front core bonded to the thick jacket; the Swift Scirocco II is a boat tail spitzer, with a polymer tip and a very thick jacket. Both offer wonderful structural integrity. The Nosler AccuBond is of similar design to the Scirocco, as is the Hornady InterBond, and Federal's Trophy Bonded Tip.
There are other designs, each with a different concept. The Cutting Edge Raptor bullets is purposely designed to have the front section of the bullet break into frangible blades, which cause a star-pattern of impact trauma, while the rear section of the bullet continues to penetrate at caliber dimension. The Peregrine BushMaster uses a hollow cavity, topped off with a bronze plug set flush with the meplat. Because air can't easily be compressed, the impact causes the sides of the bullet to expand reliably. I've used these bullets on all sorts of game, up to and including Cape buffalo, with stellar results.
Then there are the 'expanding solids', which are a twist on the older non-expanding bullets usually reserved for the thick-skinned dangerous game. The Woodleigh Hydrostatically Stabilized Solid uses a small cup at the nose to create a cavitation bubble to destroy blood-rich tissue, yet maintains the structural integrity of a monometal solid bullet. I've used this bullet on game from warthog and reedbuck to buffalo and elephant, and the design works as advertised. The NorthFork cup solid uses a similar-looking design for a tiny bit of expansion up front, yet the serious penetration that the monometal solids deliver. They worked perfectly in Australia on big-bodied water buffalo.
How does a hunter choose from among these designs? Which will be the best choice for his or her hunting application? Well, for sure, the bonded core designs, famous for their high weight retention, won't be a necessity if shooting prairie dogs is your thing. The light, frangible cup-and-core varmint designs are definitely the way to go for you. On the flip side of that coin, the hunter preparing for a brown bear hunt or a Cape buffalo safari would be best served by a tough bonded core or monometal bullet of good Sectional Density. Should you have the slightest hesitation using your .270 Winchester for an elk rifle, a premium bullet should allay your fears. Choose a load built around a heavy-for-caliber monometal or bonded core, and your elk should be in the salt. For the deer hunter, the traditional cup-and-core bullets have worked well for generations, but there's nothing wrong with hedging your bets with a premium bullet, should a funky shot angle present itself. You'll invariably need to try some examples in your particular rifle — to assure that the barrel and the load are agreeable — but if you head to shop for ammunition well-informed, you'll be a happier hunter once the trigger is pulled.