Introduction to Archery: Terminology, Definitions, and Specifications

I’ve posted reviews on here about both my Hoyt Charger and my Prime Rize. In those posts, I bounced around a little between straight up reflections on the equipment I use and background information on some of the terminology and specifications I was describing. Many people who were reading those posts probably wanted to skip right to the gear talk, while others could probably use a primer on the lingo, so I decided to separate the posts and create one that is just a backgrounder on the terminology you will encounter when beginning archery.

I shoot mainly compound bow. I have a longbow made by Rudder Bows, but I have to admit I don’t shoot it as much as I should. So this post mainly focuses on compound bow archery, with a slant towards bowhunting applications.

Parts of a Compound Bow 

Compound bows take the standard components of a bow and add some pieces of technology to make them more efficient at storing and releasing energy. Longbows and recurve bows have two or three main parts: a string, limbs, and a grip.

Parts of a longbow. Source: Michigan Hunter Ed Course

Compound bows have a riser (the vertical part you hold, with the grip), limbs (the pieces that attach to the riser and hold the cams), cams (the wheels at the top and bottom of the bow), a string (the part the arrow attaches to), and cables (the pieces that connect the cams to each other or to the limbs). The cams are what give compound bows the ability to shoot with much more power than the shooter actually holds – like any pulley system, they increase the efficiency of energy storage and reduce the amount of effort the user needs to put in. There are different styles of cams that all have their own advantages.

The axle-to-axle (ATA) length is the distance between the tips of the limbs, at the points where the cams attach. The brace height is the distance from the riser to the string when the bow is at rest. Bow speeds are measured in feet per second, and manufacturers use a standardized setup to compare speeds across different bows (IBO speed). The draw weight of a bow, in pounds, refers to the power a bow can transfer to an arrow and push it off the string. So a 40# (pound) bow will shoot with less power than a 70# bow. Hunting regulations will stipulate how much power a bow needs to have for particular species. For example, to hunt whitetails in Ontario, the bow needs to have about 40# of power, whereas to hunt moose, it needs 50#.

Compound bow measurements. Source: Hunter's Friend.
Compound bow measurements. Source: Hunter’s Friend.

Arrow Selection

(This section is an excerpt from a more thorough post about arrow selection.)

The first thing you need to know when selecting an arrow is what spine you need. Most choices in arrow selection come down to personal preference, but not spine. Arrow spine refers to the stiffness of an arrow, and it’s critical for the safety of your bow and for accuracy that you choose the correct arrow spine.

Imagine you drive a truck into the end of a horizontal telephone pole. Imagine  you drive the same truck into a tooth pick. Finally, imagine you drive it into a 2×4. While perhaps a little rough around the edges, this analogy is meant to explain what happens if you shoot an arrow that is too stiff or too weak for your bow. When the bowstring pushes the arrow off the end of the bow, the arrow flexes, stabilizing throughout the course of its flight. Simply put, if your bow is too weak, the arrow can`t flex enough; if your bow is too heavy, the arrow flexes too much. At worst, these situations could damage your bow, but they will certainly reduce the consistency and accuracy of your shooting. The rule is that heavier bows require stiffer arrows.

Every arrow manufacturer has a way of designating the spine of their arrows, and while the system used to measure spine stiffness is standardized, the systems used by manufacturers to represent spine is not. Easton’s system is generally the easiest to understand, because they use the direct measurement for “arrow deflection“, which is the way spine stiffness is calculated. With Easton arrows, the lower the number, the stiffer the arrow. 20151218_232210So a 70# bow might shoot a 340 spine arrow, while a 60# bow might shoot a 400 spine arrow. All arrow manufacturers will have charts (Easton, Carbon Express, Gold Tip) to help you identify the correct arrow spine based on your bow specifications (e.g. poundage, draw length, and arrow length). Be sure you understand how your specifications affect spine selection. Click here for a great resource to explain some of the finer points in arrow spine.

Is Speed Important?

Speed is one of the most hotly debated topics in archery and bowhunting, and it’s probably one that new bowhunters will encounter. I discussed the issue of speed more thoroughly in my post about arrow selection, but here are the basics: it’s an important component in the equation to calculate an arrow’s kinetic energy (KE), which is what ultimately kills animals (the other component is arrow mass). So it’s true that a faster bow will transfer more energy to an arrow and therefore increase KE; however, speed is absolutely not the most important part of choosing a bowhunting setup and ensuring your arrows are effective at killing.

No matter what, bows are shooting arrows at subsonic speeds, meaning that the sound of a bow shooting reaches an animal before the arrow every time. To put this in perspective, consider that a bow shooting an arrow at 280 fps is considered a great hunting setup. Now remember that sounds travels at 1,116 fps. In general, do I want a fast bow? Sure. Am I willing to sacrifice all the other factors that I consider when selecting a bow to get one that’s a bit faster? Not a chance.

How To Prioritize Considerations

When choosing a bow, people prioritize different things, and no one is right or wrong, so it becomes difficult to take someone’s word on why one particular bow is the best. You should choose a bow based on the optimal combination of factors for your preferences and priorities. You need to shoot a few and decide for yourself what is most important to you because there will always be trade-offs. Essentially, it comes down to what feels the best, and then identifying why it is that that bow feels best: is it the weight, the draw cycle, the balance, the release, the back wall? The combination of these and other factors will make a bow feel good for you, and the most important thing in choosing a bow is finding the right combination of specifications and features. You need to be sure of your equipment and your ability with it.

If you are interested in how my particular priorities led me to select a bow, check out my Prime Rize post.

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