I answered a question recently which cleared up some misinformation that I realize I’ve heard many times over the years, so I think it is worth posting about. I hope I can clear up what is apparently a common misconception as so many people are rushing out to stock up on guns and ammo in stores and online.
When buying ammunition, many people believe that the grain weight (gr) listed on the box refers to different powder charges and, therefore, power levels. This is not true. The grain weight listed refers ONLY to the weight of the projectile itself – the bullet that leaves the barrel when fired.
The confusion is understandable. It is easy to see how someone would assume that “grains” means “grains of gunpowder” or something. Grains, however, are archaic units of measurement of weight/mass, not a number of flakes of powder. One grain is 1/7000 of a pound, supposedly the weight of a single grain of wheat or barley. What is more confusing is that gunpowder charge weights are measured in grains as well, but this isn’t published on the box, as different formulas of powder can have very different weights for the same level of performance.
Any given cartridge can use projectiles of various weights, but the overall “power” of the cartridge often has little to do with the bullet weight. “Power” is determined mostly by the maximum pressure the cartridge can safely achieve. So a lighter bullet can be fired at a higher velocity than a heavier bullet within that same safe pressure range, and the added velocity of the lighter bullet (or reduced velocity of the heavier) will likely make the different weight bullets very close in “power” to one another.
An excerpt from the Hornady catalog, showing available 9mm FMJ projectiles.
For example, 9mm Luger (AKA 9mm Parabellum, 9x19mm, etc.), is the most popular and common handgun cartridge there is. 9mm loads are available in a wide variety of bullet weights, but the most common are 115 grain, 124 grain, and 147 grain. As you can see from the image above, these bullets are different lengths (the heavier ones are longer of course), but they are the same diameter (9mm, or .355 inches). Again, the grains listed is only the weight of the bullet, and doesn’t say anything about the “power.” You don’t have any “power” until you’ve loaded the bullet into a cartridge case with a powder charge and primer. The barrel length of your gun also affects power. Longer barrels allow bullets to accelerate for longer under pressure, up to a point when all the powder has burned. You can have, for example, a very hot-loaded, powerful 115-grain load, or a very light-loaded, mild 147-grain load. The maximum “power” of any given cartridge will be more or less the same with a max load of any weight bullet, with slight variations.
When purchasing factory ammunition, the overall power of most bullet weights will be more-or-less the same. The lighter bullets will move faster and the heavier bullets slower. You will usually only see a noticeable difference in power if you move up to +P loaded cartridges, or down to anything marked “reduced recoil.” When it comes to full-metal jacket (FMJ) target loads, the difference isn’t important for most purposes for most shooters. If you’re just looking to shoot at the range, you don’t really need to be concerned. Get whatever is cheap and reliable.
If you’re buying premium hollow-points for self-defense, it might matter a little more. Certain bullet weights might provide better performance in certain guns. Proper hollow-point expansion requires a certain velocity. That being said, if you’ve got a common defensive gun using a common defensive cartridge, performance will probably be just fine. The best loads on the market, such as Federal HST and Speer Gold Dot, are designed to perform properly in all common barrel lengths. Many are marked on the box whether they are intended for short-barreled, compact guns. Finding optimum performance requires a little bit of research on the various tests that have been performed in different sized guns, but again, the differences are not usually very pronounced.
So why are there so many choices? For practice ammo, some people prefer to train with a load that performs as closely as possible to that which they carry. Choosing the same grain weight usually helps with that. Sometimes different bullet weights will differ slightly in point-of-impact on the target, or might have slightly different feeling recoil. Additionally, as I stated before, there are slight performance differences with different weights, different loads, and different barrel lengths. As people demand the best performance, small changes do matter. It is the same reason that there are so many very similar guns on the market. Sometimes small differences matter, even if they are subjective. Additionally, if you have a suppressor, heavier bullets (like 147 grain 9mm), may be subsonic in your gun and thus quieter.
Most people using a handgun for defensive purposes don’t need to worry too much about different weights. Just stick with the standard weights available and they should work as desired if you’re using a reputable, high-quality defensive load. When in doubt, just get the middle weight in the range (like 124 grain in 9mm). It matters a lot more with rifle rounds. Different guns may have wildly different levels of accuracy with different bullet weights depending on many factors. After all, the shooting with rifles is usually done at much greater distances. AR-15s, for example, come with varying twist rates on the rifling, with some bullet weights being more suitable for certain rates of spin than others for best performance. Further, with hunting, different sized game may require different bullet construction for the most effective, ethical kill.
But what about the different levels of “power” in handgun loads? Why do I keep putting “power” in quotes? It is true that different loads can have varying levels of power, but what “power” is when it comes to self-defense with a handgun is very misunderstood. I will have another post in the future explaining what you need to know about the myths of handgun “stopping power.”
As always, Piece be With You.