If you’ve ever stood in the aisle of a gun store staring at shelves of ammo, wondering which box you should be adding to your stash, you’re not alone. The options for ammo are practically endless: target rounds, defensive loads, hunting ammo, match, it goes on forever. If you’ve ever wondered, what is bullet grain, or needed some assistance understanding how to determine the best bullet weight for building up your ammunition stores, you’ve come to the right place.
It’s Always Purpose-Driven
The ammo you use is just like the guns you run: purpose-driven. When you’re selecting a gun, you should first consider what it will be used for. Guns are tools, which means they should fit the task at hand even if that task is plinking at the range. After all, you wouldn’t use an AR-15 as your daily carry gun, right?
Before you attempt to decipher the difference between various bullet weight options, ask yourself what you’re using the ammunition to do. Is this ammo being used in your EDC (Every Day Carry)? Do you need cheaper ammo for high-round-count training?
General types of ammo include:
- Target rounds (Full Metal Jacket, Total Metal Jacket, and other non-expanding options)
- Defensive rounds (Hollow Point, Jacketed Hollow Point, and various expanding loads)
- Hunting rounds (Soft Point, Hollow Point, and those specifically geared toward game animals, which have different anatomy than human threats)
- Match rounds (Open Tip, Boat Tail Hollow Point, and other loads designed for consistent, precise performance)
As you can see, there appears to be some crossover in bullet type among the loads. In reality, they’re all different, partly because a round of ammo is more than only its bullet.
Anatomy of a Round of Ammo
A single round of ammunition has multiple parts, all of which work together to get the job done. Components include:
- Case
- Primer
- Propellant (Powder)
- Projectile
These components are not all created equally which is why 9mm 115 FMJ (Full Metal Jacket) rounds from two different companies won’t deliver identical results. Every part matters. This is also why you need to zero optics and train with iron sights using your intended load when you’re focused on self-defense, hunting, or competition. You will not get consistent results by mixing brands, even if the general descriptions appear to match. Sometimes the variation will be minimal and sometimes the difference will be glaring.
What is Bullet Grain?
Bullet weight is measured by grains. This might be shortened to “gr” on the box of ammo. Higher numbers equate to heavier bullets, and vice versa. It might seem reasonable to translate “grain” as having to do with the propellant in the round, but this measurement has nothing to do with gunpowder.
From a technical perspective, one single grain is equal to 1/7000 of one pound. To give you a rough idea of what that means, 9mm bullets range from as little as 50 grains or as many as 200. That demonstrates the extremes, though; the majority of popular 9mm ammo falls more in the 115 to 185 grain range. For comparison’s sake, a 1979 quarter weighs approximately 84.8 grains and a AA battery weighs 385 grains. If you’d prefer ounces, a 124 grain 9mm bullet weighs about 0.28 ounces, which can be contrasted with the standard Keurig cup, weighing in at 0.5 ounces.
After realizing just how small bullets really are, you might be wondering how they can possibly be effective. Basically, it comes down to the aerodynamic design of the bullets, the impetus created by the propellant, and how much the barrel length helps or hinders velocity and energy. Is there more to it? Yes, but for now let’s stick to the highlights.
Heavy or Light Bullets for Self-Defense?
There is no single answer to whether you should use lighter or heavier bullets for defensive purposes. The various components mentioned above work together to deliver different results, so it’s more about the specific load. It might seem logical to assume a heavier bullet will have the most extreme effect on the threat, but that isn’t necessarily true.
The 45 ACP is a good example of a heavyweight bullet that moves a bit sluggishly and, as a result, doesn’t always deliver for overall performance. Bullets traveling at slower speeds also drift and drop more quickly, meaning they lose velocity and energy, fail to impact targets with as much overall power, and don’t create as large or devastating a wound cavity. That is not to say there aren’t effective 45 ACP rounds on the market for defensive purposes, but only that the average factory load is not going to create the terminal performance many gun owners want out of a defensive load. Some factory loads are specifically designed for superior performance, such as those from Hornady.
For comparison’s sake, take a look at these ballistics testing tables evaluating different calibers of Hornady Critical Defense:
| Caliber/Load | 380 Auto 90 grain FTX | 9mm Luger 115 grain FTX | 45 Auto 185 grain FTX |
| Total Penetration | 10.25 inches | 11.25 inches | 13.75 inches |
| Max Cavity | 1.6 inches | 2.25 inches | 2.25 inches |
| Depth to Max Cavity | 2.0 inches | 2.25 inches | 3.5 inches |
| Initial Penetration | 0.5 inches | 0.25 inches | 0.75 inches |
| Retained Weight | 89.0 grain | 115.0 grain | 184.0 grain |
| Retained Weight % | 98% | 100% | 99% |
| Expanded Diameter | 0.51 inches | 0.55 inches | 0.66 inches |
| Velocity (feet per second) | 1000 feet per second, muzzle | 1140 feet per second, muzzle | 1000 feet per second, muzzle |
To get a more visual understanding of the data, take a look at the ballistics diagram below.
As you can see in the table above, the maximum cavity using both 9mm and 45 Auto (Auto being the same ammunition as ACP) was 2.25 inches. However, the 9mm created its maximum cavity more quickly than the 45 Auto. If you’re more confused now than before, you’re not alone. This example is simply to show you that bigger is not necessarily much—if at all—better, and to do your homework on your chosen caliber and ammunition.
As you can see in the table above, the maximum cavity using both 9mm and 45 Auto (Auto being the same ammunition as ACP) was 2.25 inches.
Does Trajectory Matter?
As you might expect, heavier bullets have more of an arcing trajectory than lighter bullets. Their additional weight drags them down to earth more quickly than their lighter counterparts. Does this automatically mean a lighter weight bullet is the best option? No. As with choosing any load, you need to consider its purpose.
If your carry gun of choice is chambered in 9mm, you might choose target rounds that weigh only 115 grain and defensive loads that weigh 147 grain. The target loads suit your needs because they’re affordably priced, feed consistently in your gun, and provide relative accuracy during training. Your heavier defensive loads may or may not deliver greater overall terminal performance than loads with 115 grain bullets. As mentioned before, you must consider the round as a whole rather than only by its bullet weight.
The trajectory does matter and is dependent on what you’re doing with the ammo in question. If you’re trying to ring steel at 50 yards with your 9mm, you’re going to be interested in a lighter bullet capable of a flatter shooting trajectory. However, if you are focused on self-defense, you’re unlikely to be so concerned with longer-range shots.
Does the Gun Matter?
Yes, it matters what gun you use with a specific round. From its barrel length to its recoil spring, The design of the gun affects how well it cycles certain loads as well as how accurate your shots will be. This means that just because a specific round works well for your friend doesn’t translate to it also being a top performer in your gun.
Barrel length is frequently mentioned when getting into ballistics. It’s accurate to say a snub-nosed revolver, or another handgun with an extremely short barrel, will not produce the same velocity and energy as a full-sized handgun. However, sometimes the differences in velocity produced using different barrel lengths is negligible. Don’t assume an extra 0.5 inches will result in an incredible increase in velocity.
What is the grain of a bullet and the bottom line on bullet weight?
Here is the bottom line. The bullet grain you should be getting depends on your gun and your needs. In addition, certain manufacturers produce higher-performing rounds, so it pays to do your homework. Once you believe you’ve found the right round for your purposes, try it out at the range (that goes for defensive loads, too). Familiarizing yourself with your ammunition is a wise idea, as is training with the defensive ammunition you intend to use in your carry gun. After all, when your life is on the line, you need to be able to rely on your gun and ammo to perform as expected.
