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Understanding "Bonded" Bullets—Dispelling the Myth
There are several different processes of electro and/or electro chemical bonding of the bullet jacket to its core, but we will not discuss those processes here, other than to state that such processes are used to bond a bullets jacket to its core material.
Just because a bullet was manufactured via one of the "bonding" processes, does not magically make that bullet better than a normal "cup & core" pressed bullet for any and all purposes—not even close. I often get emails (which is why I am writing this article) from customers who want a bonded bullet for this or that application and only a bonded bullet will do, which means they lack understanding.
If bullet construction (i.e. hardness, malleability, etc.) is properly designed for a range of impact velocities into a range of known mediums, (flesh, bones, guts, etc) it matters little that the core material is bonded to the jacket. As an example, the Speer Gold Dot 90 grain .355 inch dia., (380 Auto bullet) bullet is "bonded" as are all Gold Dot bullets. The same diameter 90gr. JHP bullet made by Sierra is standard cup and core swaged/pressed construction, but when we fire either bullet into ballistic gelatin at the velocity ranges of our 380 Auto +P or "Standard Pressure" ammo, those two bullets act nearly identically. This happens because even though they are made by different manufacturing processes, they are both utilizing materials that match the expected impact speeds with the expected mediums. The shooter gains no advantage by using the bonded bullet over the cup & core bullet IN THIS PARTICULAR EXAMPLE and the medium (probably a human) receives no more damage with one projectile over the other, within the expected velocity range. Yet people who do not know any better, simply insist on having that magic "bonded" bullet....
Another example would be the Sierra 180gr. Spitzer flat base .308 bullet when fired from an 06. I have killed or seen killed dozens of black bear, deer, hogs, elk, etc. with this bullet at impact speeds of 2750 fps to 2100 fps and within that velocity range on medium to large game animals, the bullet never fragments or "fails" in any way. It simply mushrooms nicely, holds together and penetrates deeply enough that I have never recovered one from a black bear shot at any angle. I could not ask for better performance from a big game bullet, whether it is "bonded", partitioned, or sprinkled with Holy Water. Yet this Sierra bullet is an old technology, cup & core bullet. The added benefit of this bullet is that it is cheap to purchase, which means I get to shoot a lot of them without going broke and lots of shooting at lots of targets, is a very good thing. However, when this same Sierra bullet is fired from one of the various 300 magnums at a muzzle velocity of 3100 fps and the impact distance is close enough that the bullet is exceeding 2750 fps when it hits a game animal, the bullet will SOMETIMES rupture and fragment and therefore not penetrate as deeply as may be desired in SOME cases on a large animal such as elk, but on a smaller deer, it does not matter if the bullet ruptures as a thin bodied deer does not require much penetration to be killed. A "bonded" bullet will also come apart in degrees if the impact velocity is greater than the material of the bullet is designed to withstand for the medium it strikes.
In short, ANY bullet, regardless of "bonding" (bonding of any type) or partitioning or any other type of construction, must be made of the right combination of materials to withstand the range of impact velocities into the range of mediums you are going to shoot. "Bonding" is just one tool, that if properly matched with other criteria, gives some useful options to bullet construction, but standing alone, in-and-of itself, "bonding" means very little.