How to build heavy hunting arrows

Heavy hunting arrows are wildly popular these days.

Whether you want just an overall heavy arrow or you want to add weight specifically to the front of the arrow to boost an arrow’s FOC, there are products that can help achieve your goals.

Let’s start with heavy arrows. Arrow weights vary wildly across manufacturers and individual shafts, but, generally, the typical weight for today’s hunting arrows is between 7 and 9 grains per inch, depending on the spine.

Once you get to 10 grains per inch and over, now you’re talking about some serious heavyweights. Easton’s 5mm FMJ arrow shaft in a 340 spine weighs 11.3 grains per inch, for example.

A 30-inch bare shaft would weigh 339 grains. By the time you add an insert, vanes and a broadhead, you could easily have an arrow weighing more than 500 grains.

Whatever you do, don’t simply increase the spine of the arrow you’re shooting in order to get a heavier arrow. That same Easton 5mm FMJ weighs 10.2 grains per inch in a 400 spine. If a 400-spine arrow is what your setup calls for, don’t choose the 340 simply to get more weight.

Stick to the spine recommendations for your draw weight and arrow length, since that will give you the best performance.

Now let’s take that heavy hunting arrow and add on a heavy broadhead. The 100-grain broadhead is considered standard, so maybe you increase to a 125-grain head, or maybe even 150 or 175. The Northern Broadheads Wide Cuts weighs in at a whopping 175 grains.

Northern Broadheads Wide Cuts 175-grain

But before you install that heavy broadhead into your heavy arrow, let’s swap out the standard aluminum insert that comes with your arrows for a brass one. Gold Tip’s standard, Accu-lite threaded insert for its .246 diameter arrows weighs 11.4 grains. But Gold Tip also makes a brass insert for its .246 arrows that weighs 100 grains. Simply swapping inserts boosts your arrow weight by 88.6 grains.

Gold Tip .246 Brass Insert

Black Eagle offers a stainless steel insert weighing 28 grains for its Spartan arrows to which you can add brass weights that weigh 30 or 75 grains. Those weights are the same diameter as the insert, and they have a threaded post which screws into the back of the insert. And they’re made so you can stack them, one behind the other.

Black Eagle Spartan 30-grain Brass Insert Weight

Other arrow and component manufacturers offer a variety of heavy inserts and insert weights to add weight to the front end of your arrows to boost the FOC. That stands for “front of center,” and it refers to the percentage of arrow weight that’s at the front end of the arrow.

Boosting an arrow’s FOC can help it stabilize in flight and to punch through hide, bone and tissue.

Understand, however, that when you increase the weight up front, you weaken the arrow’s spine. Most manufacturer spine charts make spine recommendations based on 100-grain points. If you use a 175-grain head with a 100-grain insert, you will want to go with a stiffer arrow.

So let’s take that 30-inch, 340-spine Easton FMJ that weighs 339 grains for the bare shaft. We will add Easton’s 75-grain stainless steel insert, and then screw in a 175-grain Northern Wide Cut. Before fletchings, we’ve got an arrow that weighs 589 grains and has an FOC of about 20 percent.

That’s a heavy arrow.

Lancaster Archery Supply has a full line of hunting arrows you can look through to compare weights and find the one that’s as heavy as you want it to be. We’ve also got a full line of arrow components that you can look through to find the inserts and points that will work for your arrow build.

Bowhunting Tech Tip: Arrow Spine vs. Arrow Weight

In this video, LAS TechXpert P.J. Reilly addresses the difference between arrow weight and arrow spine.

An arrow’s spine determines how much the shaft flexes when it leaves a bow. Archers want their arrows to flex some, but not too much.

Arrow weight refers to how much the arrow actually weighs. That weight can change as you look at arrows of different spines, but simply choosing a different arrow spine in order to change your arrow’s weight is not a good idea.

We sometimes see bowhunters opt for weaker arrows when they want to cut arrow weight, or choose stiffer shafts if they want a heavier arrow. Either can cause problems with accuracy, especially if a fixed-blade broadhead is added to the shaft. Such broadheads tend to magnify flight problems.

Lighter arrows fly faster than heavier ones, but heavy arrows generally result in better penetration. Depending on what they’re hunting and where, bowhunters might prefer a heavy arrow or a light one.

Bowhunters choosing an arrow should stick with the spine recommended by the manufacturer. That recommendation will be based on draw weight, arrow length and point weight.

If bowhunters want to change their arrow’s weight, they can opt for heavier or lighter shafts without changing spine. They can also increase or decrease point weight, but then that could affect the manufacturer’s spine recommendation.

What is Kinetic Energy and Why does it matter?

What better time for a physics lesson than the start of the fall bowhunting seasons?

If you’ve never heard the term mentioned, you should familiarize yourself with it before you head out into the field with a bow and arrow in pursuit of wild game.

Kinetic energy.

What is it?

According to physicsclassroom.com, kinetic energy is “the energy of motion”  ‑ or, the energy possessed by an object in motion.

The amount of kinetic energy a moving object possesses depends on two factors – its weight and its speed.

The heavier an object is, and the faster it’s moving, the greater its kinetic energy.

In the bowhunting world, archers should be concerned about the amount of kinetic energy (KE) carried by their arrows as they hit game animals.

An arrow needs sufficient KE to punch through hide, tissue and possibly bone. And generally speaking, the bigger the animal, the greater an arrow’s KE needs to be to carry it through the vitals.

KE, incidentally, is measured in foot-pounds.

You can think about KE this way. Let’s say a ping-pong ball and a golf ball both traveling at 30 mph hit you in the head. They’re both about the same size traveling at the same speed, but the golf ball is heavier, and is obviously going to hurt more. Its KE is much higher than the ping-pong ball’s.

To calculate your arrow’s KE, you will need to weigh it as you’d shoot it. That is, weigh your exact hunting arrow, with the broadhead attached.

You want to come up with your arrow’s weight in grains, so adjust your scale accordingly.

Next, shoot your arrow through a chronograph to come up with its speed.

Once you have the weight in grains and the speed you can complete the following equation:

Velocity squared times weight divided by the constant 450,240.

(The constant number is derived from the conversion of grains to pounds, while factoring in the effect of gravity on mass.)

So let’s say you have an arrow that weighs 400 grains that flies at a speed of 290 feet per second.

Your equation would look like this:

290 x 290 x 400 / 450,240 = 74.72 foot-pounds of KE.

What do you need to get the job done in the field?

There are a number of charts that recommend a certain amount of KE for game animals of different size.

Generally, the recommendations are as follows:

Kinetic_Graph

 

What can you do to boost your arrow’s KE?

For starters, you want to make sure you are maximizing the available KE by tuning your bow so your arrows fly straight. A fishtailing arrow won’t fly as fast as it could. And make sure you’re using razor-sharp broadheads. The more energy it takes to push an arrow through an animal, the faster it’s going to slow down.

You can shoot a heavier broadhead. That’s going to slow down your arrow a bit, so you’ve got to repeat the KE calculation to make sure you’re getting a benefit from the switch.

You can switch to a heavier arrow shaft. It’s also going to fly slower, so be sure you recalculate your KE.

And make sure you don’t change the arrow’s spine when you switch to a heavier shaft.

(Click here for a discussion about arrow spine vs. arrow weight.)

Compound bow shooters can increase the draw weight of their bows by turning the limb bolts clockwise, provided they’re not already at the maximum weight limit.

Be sure to turn the top and bottom bolts exactly the same. That is, if you put half a turn into the top bolt, do the same to the bottom.

Recurve archers who shoot takedown bows might want to switch to limbs with a heavier draw weight.

Increasing draw weight increases arrow speed regardless of the bow.

Of course, that can make your bow difficult  – if not impossible – for you to draw, so proceed with caution.

Know your KE before you hit the woods this season. It can mean the difference between success and failure.

Arrow spine vs. arrow weight: Don’t be confused

In the Lancaster Archery Supply Pro Shop, we hear it all the time.

“I want to switch to a lighter arrow to get more speed.”

That’s usually not a problem, as long as you don’t confuse arrow weight with arrow spine. Too often, that’s exactly what archers do. Someone shooting a bow with a 70-pound draw weight and a 29-inch draw length will grab a 400-spine arrow to replace the 340-spine arrow they’ve been shooting. They think that’s the right way to reduce arrow weight.

It’s not.

When we talk about an arrow’s spine, we’re talking about how much it flexes. We’re talking about its stiffness. Every arrow should flex when it leaves the bow. But it should only flex a certain amount. If it flexes too much – weak spine – then its flight will be erratic. If it doesn’t flex enough – stiff spine – then the arrow will have no forgiveness. Consistent accuracy usually suffers in either case.

Choosing the correct arrow spine for your setup depends on your draw length and draw weight. Draw length is important, because that determines how long of an arrow you need to shoot. And the longer a shaft is, the more it’s going to flex. Draw weight is factored in, because that determines the amount of force pushing the arrow.

Every arrow manufacturer has a spine-selection chart, so you know which shaft to choose for your draw weight and arrow length. (Some even factor in the bow’s speed rating, since faster bows exert more force on an arrow.) And every shaft bears its manufacturer’s spine rating.

Unfortunately, the numbering system for spine ratings is not uniform from manufacturer to manufacturer. So don’t assume the numbers you see on shafts across manufacturers are comparable.

Beside or below the spine rating, most shafts usually also are stamped with their weight in grains per inch. And this is where archers can get confused.

Let’s take the Easton Bowfire, for example. The 330 shaft weighs 9.6 grains per inch. The 400 shaft weighs 8.5 grains per inch. Logic might tell an archer that, in order to lighten their arrows, they should switch from a 330 to a 400. Bad move. The 400 arrow is lighter, but it’s also weaker, and so tuning could be a real problem.

If you want a lighter arrow, stick with the recommended spine rating, but switch to a lighter shaft. Again, that 330 Bowfire shaft weighs 9.6 grains per inch. A 330 Easton Hexx, however, weighs 7.9 grains per inch. Same spine – lighter shaft.

Just for comparison, take a look at these arrows. All measure 29 inches from the insert-end to the bottom of the nock throat. All include 100-grain points, and three Blazer, 2-inch vanes. And all are the correct spine for the archer shooting a 70-pound bow, according to the manufacturer’s chart.

Shaft                                Weight

340 Easton Full Metal Jacket     482.2 grains

330 Easton Bowfire              433.6 grains

330 Easton Hexx                 382.1 grains

So you can see here, there are opportunities to change the weight of the arrow, without deviating from the spine chart.