How to Choose the Best Hunting Arrow - Heavy vs. Light
Curt Wells and Randy Ulmer [video] explain the importance of momentum and penetration when choosing heavy vs. light arrows for bowhunting.
Whether you bowhunt with a recurve bow, a longbow, or a compound bow, choosing the best hunting arrow is critical to success. That arrow must be the correct length, straight, and stiff enough to fly well out of your bow.
Just as critical is arrow weight because that affects penetration and bowhunting is all about achieving two-hole penetration, profuse bloodtrails, and quick, humane death.
The eternal debate over which arrow is better - light and fast or heavy and slow - will never end, but it's really very simple physics. Heavy arrows penetrate better.
The first reason why it's important to choose the best hunting arrow is because once an arrow leaves the string it ceases to be propelled. Force, in the form of drag, immediately begins to work against the arrow, causing it to decelerate.
That force has a greater effect on the faster arrow (see Newton's Second Law of Motion) so it decelerates faster than the slower arrow. When an arrow hits an animal, the difference in deceleration can be dramatic because the heavier arrow will have a slower deceleration rate, thus penetrating deeper.
The Best Hunting Arrow Is?
If this were not the case traditional archers seeking maximum penetration would shoot the lightest arrows they could find, when just the opposite is true.
Yet another testament is the poor arrow penetration often seen on hunting shows on television. My guess is it's the result of some bowhunters who believe the best hunting arrow is a light arrow. Unfortunately, when bowhunters only focus on maximum arrow speed they often end up on a misguided quest.
Most bowhunters cite kinetic energy when referring to the penetration potential of their bow setups but it's really momentum that determines how well an arrow will drive through an animal. Let's look at the numbers in the table below, which compares three bow set-ups, a compound with a light arrow, a compound with a heavy arrow, and a comparatively slow traditional bow with an ultra-heavy arrow.
|Arrow Weight ||Arrow Speed ||Kinetic Energy ||Momentum |
|350 gr. ||340 fps ||89.75 ft. lbs. ||.527 Slug/ft. per. sec |
|480 gr. ||290 fps ||89.54 ft. lbs. ||.617 Slug/ft. per. sec |
|750 gr. ||175 fps ||50.95 ft. lbs. ||.582 Slug/ft. per. sec |
Note the high-speed setup generates nearly equal kinetic energy to the compound with the heavier arrow, but the momentum is significantly higher with the heavier, slower setup. Most notably, and maybe even a bit surprising, the very slow and very heavy traditional arrow creates much less kinetic energy but still generates more momentum than the compound setup with the light, fast arrow.
Why Momentum Matters
So what is the right arrow weight? That's a question that must be applied individually based on your draw weight, draw length, and species of game being hunted. A deer hunter can get away with a lighter arrow when the shot is perfect. But what if it isn't? That is when you need all the momentum you can muster.
Personally, I believe the best hunting arrow/broadhead combination in one that weighs at least 400 grains. My typical arrow for most species weighs around 450 grains but for 2015 I'm increasing my arrow weight by shooting a 29-inch Easton Deep Six XD shaft with a 100-grain Rage Hypodermic broadhead and a Lumenok for a total arrow weight of 488 grains.
At my draw length of 30 inches and with a draw weight of about 67 pounds, that arrow is generating more than enough momentum for any North American big-game species.
If you have a shorter draw length, and/or you shoot less draw weight, choosing a lightweight arrow shaft to gain speed is actually counterproductive when it comes to penetration.
I know that doesn't sound logical, but think of the traditional archer shooting a heavy, slow arrow that passes completely through a 1,500-pound bull moose. If you're not confident that your lightweight, fast arrow can do that, then you're not shooting the best hunting arrow.
Strive for Maximum Penetration
The only tangible disadvantage to a heavier shaft is the increased trajectory of the arrow in flight. That makes yardage estimation more critical but a good rangefinder mitigates the trajectory problem. Experienced western bowhunters, who tend to shoot game at longer distances, often opt for a heavier shaft because it is less susceptible to wind drift and it hits harder when it does connect.
Certainly, there are many factors, like bow tune, fletching and broadhead design, that determine how well an arrow performs in flight and on impact.
Still, some ask if their arrow zips through a deer now, why do they need more penetration? The answer is, you choose the best hunting arrow and broadhead combination not for what it will do when the shot is perfect, but for what it can do for you when your shot isn't perfect.
There's no such thing as overkill.