How to Choose the Right Rifle Cartridge for Your Hunting Needs

The Ins & Outs of Hunting Ammo Selection

by John Warren

At least once a week, someone is in my DM’s asking, “What’s the best caliber for hunting x animal?” Choosing the perfect rifle cartridge can seem like a complex task. With a plethora of options available, it’s essential to understand the factors that should influence your decision. This article aims to guide you through the process, helping you select the right rifle cartridge based on your specific needs and preferences. It is important to note that there is no perfect cartridge despite what the forums tell you; each one has pros and cons.

*Note: There are many projectile types, but in this article, I am discussing modern hunting bullets with high ballistic coefficients.

Understanding the Basics of Rifle Cartridges

Let’s take a moment to learn the basic terminology before we begin the selection process.

• Caliber: This term refers to the diameter of the projectile (bullet). It’s commonly measured in inches or millimeters. For example, a 308 caliber bullet is .308”. It is also important to note that different cartridges can have the same projectile diameter. The 30-06, 300 Win Mag, and 30-30 all have the same .308” bullet diameter. What makes these calibers different from one another is bullet weight and the amount of powder used.
• Casing: The casing is the brass container that holds the powder charge behind the projectile. Its shape and length vary depending on the specific cartridge desired.
• Cartridge: The cartridge is the complete package – a bullet of a specific caliber housed in a casing. For example, a 300 Winchester Magnum is a .30 caliber bullet inside of a .375 H&H Magnum casing that has been modified to accept a .30 caliber projectile.

The Physics of Recoil & Size Relationship

Recoil is the backward force you feel when you fire a rifle. It’s a result of Newton’s third law of motion – every action has an equal and opposite reaction. Large, heavy bullets fired at high speeds result in more significant recoil, which, when not managed properly, can affect your marksmanship.

Debunking Common Misconceptions

When discussing cartridge selection, people usually have three standard lines of thought.

• Size is king: A larger caliber isn’t necessarily better. It’s crucial that a rifle fits the shooter. There is a point of diminishing returns. When a lightweight rifle is chambered in a caliber with a high recoil impulse, your ability to employ the rifle comfortably is diminished. Nobody wants to get beaten up by their rifle every time they shoot it. Put another way, it diminishes your chance for a first-round vital zone radius hit.
• Speed is king: While speed can result in flatter trajectories and more kinetic energy on target, it has a cost you pay for in barrel life and recoil.
• Magnum is king: I love magnum calibers, especially the 300 Win Mag, but non-magnum cartridges can be just as effective, especially with modern hunting bullets. Both the 30-06 and the .308 have killed a lot of two and four-legged critters in their day.

Key Factors for an Ethical Harvest

For ethical and effective hunting, consider these factors:

• Penetration: The bullet should be able to reach and pass through the animal’s vitals, causing maximum damage. Penetration requires momentum. Speed is a factor, but we calculate momentum as the product of an object’s mass and its velocity, so speed alone won’t do it. We should also consider the projectile shape, material, as well as target density
  • An easy way to think about this is that a truck moving at 1 meter per second has more momentum than a tennis ball moving at 30 meters per second.
• Placement: The location of the shot is paramount. Even a high-power cartridge won’t guarantee a quick kill if the shot is outside of the animal’s vital zone radius.
• Effective Wound Channel: This refers to the damage caused by the bullet as it passes through the body. A well-chosen bullet will create an effective wound channel via expansion, leading to a quicker kill.

Choosing the Right Rifle Cartridge for You

When selecting a rifle cartridge, consider:

• Purpose: What game are you hunting? The size of the animal will influence the bullet size you need. You wouldn’t take a shot at an elk with a .22 caliber. There are some general rules of thumb that I will discuss later on.
• Recoil Tolerance: Everyone has a different tolerance for recoil. Choose a cartridge that you can shoot comfortably and accurately.
• Availability: New ammo pops up every month, and its availability can vary significantly. Switching over to a newer cartridge, like 6.5 PRC took me a long time. My thought is that if I can’t walk into a Bi-Mart in the middle of nowhere and buy a box of ammo, then I won’t use it.
• Budget: How much a box of ammo costs is a huge deal, especially in the current market…thanks covid. Newer cartages with modern projectiles that are made in low volumes will cost more per box than those that have more time on shelves.
  • Economies of scale say that the more of a product a company produces, the more likely it is to cost less per unit. Once many people own a product, the market becomes saturated. To keep selling, companies often lower prices as an additional value.
  • A caveat to that is learning to reload, but that is a whole other topic of discussion.
• Opinions: Don’t let others’ opinions sway your decision. Choose what works best for you but be realistic.

Modern Hunting Cartridge Comparison

Something to note about recoil impulse: you can help lessen the recoil impulse with a muzzle brake, suppressor, or by adding weight to your rifle. It’s all about balance and what you are comfortable behind shot after shot.

Thoughts and Rules of Thumb

There are many conflicting opinions on the subject of cartridge selection, but most experts can agree on two points.

1. Shot placement is king. Placing a projectile within the animal’s vital zone radius surpasses almost all other areas of terminal performance.
2. Bullet to bullet, a higher velocity impact will be more lethal than a lower velocity impact.

My rule of thumb on an ethical distance is threefold: bullet expansion, energy, and time of flight. A bullet must be able to expand fully, retain at least one ft-lb of energy per average pound of animal and take less than one second to reach the target.

Obviously, other variables factor in, such as environment, marksmanship ability, and recovery. But when I build a rifle, that is what I use to set the threshold distance. Most bullet manufacturers say that a bullet requires a minimum velocity of around 1,800fps and should not exceed a maximum of 3,000fps to expand effectively.

Consider This: If I were hunting Rocky Mountain or Roosevelt Elk in my home state of Oregon and only had a 6.5 Creedmoor, I would look at the following.

At 700 yards, a 140gr 6.5 Creedmoor Berger Target Hybrid with a muzzle velocity of 2,850fps will retain a velocity of 1887fps. That is more than enough for expansion, but the energy on target is only 1,107 ft-lbs. A bull elk averages 800-1,200 pounds. I would caution toward the higher number, meaning we do not meet the second criterion. So, 700 yards is too long of a shot to be ethical with this caliber.

If we move the range to 600 yards, we have a velocity of 2,011 fps. Our energy is 1,257 ft-lbs. And our time of flight is 0.75 seconds. In a vacuum, this would be what I would consider the ethical threshold. Nondeterministic variables such as wind, shooter, and variations in muzzle velocity will chip away at that range quickly. Depending on how much you train, you might only be comfortable taking a shot at 500 yards, your distance may be shorter, but you get where I am going. Animal hide thickness is also a factor. For something like a black bear, I would 2x the energy needed. Below is a range card for the previously discussed cartridge.

Threshold Distance vs. Viable Distance

I know…This article is supposed to be about choosing a rifle cartridge. But with how the internet is, I need to clear something up. Just because the bullet can, does not mean you should. The threshold distance lives in a vacuum. It is a starting point that only includes numbers.

Viable distance is all about maximizing the percentage of a first-round lethal hit on a target. Meaning your projectile hits the vital zone and expands with enough energy to be lethal. It includes the environment, the rifle system, the nature of the target, and the shooter’s ability to hit a target accurately. I will discuss the difference between these in detail in another article.

Caliber/Animal Brackets

The above are guides, not commandments.

The Best Caliber for Hunting

Remember, the best rifle cartridge is the one that suits your specific needs. Personally, I build rifles for specific species separated by size. If I am hunting antelope or deer, all the factors above dictate that I can use a smaller caliber, like a 6.5 Creedmoor, and be ethical out to a respectable distance. State hunting regulations will often dictate the minimum caliber allowed for a particular species, so make sure you always abide by those.

In the comments, let us know what you use, what you hunt, and why!