Bonded Bullets: What are they and when should you use them?

     When hunting any game species regardless of its size, it is of paramount importance that the hunter not only choose an appropriate caliber and cartridge, they must also choose an appropriate bullet design because not all bullets are created equal. In fact, modern bullet manufacturers provide shooters with a wide range of jacketed bullet types and designs in numerous different calibers and weights and thus, with careful selection, a hunter can choose a bullet appropriate for hunting game species ranging from rabbits to bears. However, in order to humanely dispatch an animal, the bullet the hunter chooses must have the integrity to penetrate the animal’s body and reach its vitals and thus, bullet manufacturers address this issue by creating bullets with various types of internal construction.

 The different types of rifle bullets –

     In fact, modern jacketed rifle bullets are generally divided into two categories consisting of those with round noses and those with pointed noses (called Spizters) and each type is specifically designed to perform at different muzzle velocities. Of course, when a hunter refers to jacketed rifle bullet performance, what he really means is the muzzle velocity at which the bullet expands, the rate at which it expands, its final diameter after expansion and, its weight after expansion. Thus, for small game species such as varmints where explosive bullet performance is preferred in order to generate very high levels of hydrostatic shock, hollow point spitzer bullets are often chosen. But, when hunting medium to large game species, both round-nose and spitzer bullets with soft noses (exposed lead points) are the best choice due to their controlled rate of expansion.

 Why choose an expanding bullet? –

      So, why should you choose an expanding rifle bullet rather than a “solid” rifle bullet? Well, the answer to this question is that expanding bullets create a larger temporary wound cavity as well as a larger permanent crush cavity which, in turn, results in greater lethality for a more humane kill. But, the problem with designing an effective jacketed, soft point, rifle bullet is that the bullet must be designed to expand reliably over a wide range of muzzle velocities and, the way that bullet manufactures do so is to vary the thickness of the copper jacket at different points along the bullet’s ogive (the curved section of a bullet) with the thinnest point located at the tip and the thickest point located at the base. Thus, upon impact with a game animal’s body, the pressure generated at the tip of the bullet forces the exposed lead core down into the copper jacket which then causes the jacket to rupture and peel back toward the base of the bullet.

 Non-bonded cores vs. bonded cores –

     However, in many bullet designs, inertia causes the lead core of the bullet to separate from the jacket and slide forward upon impact which, in turn, leaves an empty space at the base of the bullet that reduces the bullet’s weight and thus, decreases its depth of penetration. Consequently, you will often see bullet manufactures and outdoor writers refer to a bullet’s “retained weight”.

     But, the large majority of conventional jacketed rifle bullets are made by inserting a cold lead alloy core inside of the copper jacket prior to forming and these cores are generally lubricated prior to insertion in order enable the assembly machines to handle them without stoppages. However, even if the lead cores are not lubricated, a thin layer of lead oxide starts to form on the surface of the core as soon as it leaves the mold and, in most cases, either the lubricant or the lead oxide layer is responsible for the separation of the bullet’s core from its jacket upon impact.

     Consequently, modern bullet manufactures address this issue in various ways such as forming either a partial or complete partition inside of the copper jacket below the bullet’s ogive or by bonding the bullet’s core to its jacket which can be accomplished in one of several different ways. For instance, some bullet manufacturers first melt the lead core alloy and then pour the molten alloy into the jacket before the final forming process while others use an electrochemical process similar to plating while others use an undisclosed process. However, regardless of the process used, the end result is that the bullet’s lead alloy core physically adheres to its jacket which prevents separation of the two components.

Advantages and disadvantages of each type of bullet –

     However, the process of bonding the bullet’s core to its jacket also incorporates an extra step in the bullet forming process which, in turn, increases its cost. In addition, in order for a given bullet design to provide a shooter with dependable accuracy, each bullet manufactured must be identical. But, due to the extra step involved in manufacturing bonded bullets, there is a greater likelihood of introducing slight variances in each bullet. Yet, due to their greater integrity, bullets with bonded cores are able to penetrate more deeply; especially when encountering bone.

     On the other hand, bullets that lack bonded cores are less expensive to manufacture. Also, due to the fact that fewer steps are required to manufacture them, non-bonded bullets can sometimes be slightly more accurate than those with bonded cores. But, at the same time, bullets that lack bonded cores can, and often do, experience core separation upon impact and thus, they often penetrate less deeply than bullets with bonded cores due to their lesser retained weight.                                                                                                                                 

 When to choose each type of bullet –

     So, when should you choose one type of bullet over the other? Well, bonded bullets are a better choice when hunting large game species with relatively thick skins and dense muscle tissue such as moose, bison, or bears as well as many African game species. In addition, they are also a better choice when a hunter is forced to take a less than optimal shot so that the bullet is forced to first penetrate bone before reaching the animal’s vital organs.

     In contrast, non-bonded bullets are often a better choice when hunting smaller, light-bodied, thin-skinned, game species such as deer and antelope because it is far easier for a bullet to reach the animal’s vitals. However, they also often perform well when hunting larger, heavier, game species when the shot is placed is behind the shoulder rather than through the shoulder. But, non-bonded bullets are much less forgiving when used to hunt big game animals and thus, less-than-ideal shot angles often result in insufficient penetration.

 Conclusion –

     So, in conclusion, a bonded bullet is simply a bullet in which the manufacturer has used one of several different methods to physically bond an internal lead alloy core to an external copper jacket in order to create a jacketed bullet with a greater degree of integrity in order to increase the bullet’s retained weight after expansion for deeper penetration. Therefore, due to their greater expense, many hunters only choose bullets with bonded cores when hunting large game species with relatively thick hides and dense muscle tissue or, when they believe that they may be forced to shoot their chosen quarry at a less than ideal angle so that the bullet will be forced to penetrate bone before reaching the animal’s vital organs. However, despite their greater expense, bonded bullets do offer hunters an increased level of performance over those with non-bonded cores and thus, they are worth considering even when hunting light-bodied, thin-skinned, game species.

Written by,

Bill Bernhardt

Outdoor Professional

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