CHAPTER 2: LENGTH, STRAIGHTNESS, & MASS
PROPER LENGTH OF AN ARROW
Safety first! Arrows that are too short for your bow setup are a serious hazard. Even an arrow that is just long enough is too short. The best safety practice is to make sure your arrows sit at least 1" forward of your arrow rest when the bow is at full draw.
A little bit of extra arrow length gives the arrows an important margin of safety. An arrow that is too short can lodge behind the arrow rest at full draw. If this happens and you don't notice it before you fire the bow, the arrow could buckle and snap upon release ... possibly sending shards of carbon into your bow hand or arm. This is called an obstructed path shot ... which is a very very bad thing. See our Arrow Safety Warning page for the gruesome details.
Unfortunately, some shooters (and shops) deliberately cut arrows too close to the arrow rest, usually to minimize arrow mass and get the fastest possible arrow speeds. But this practice regrettably comes at the expense of safety. The extra 1-2 fps you gain by cutting arrows "just long enough" isn't worth risking an arrow shaft stuck in the forearm. So never shoot arrows which are too short.
On the other hand, shooting an excessively long arrow isn't so smart either. If your arrow length is excessive, your arrow will have additional (and unnecessary) mass and the additional length will increase the arrow's spine requirements (more on this in Chapter 3). Basically, extra long arrows significantly decrease your arrow speeds and limit the performance of your bow.
So choosing a safe yet optimally performing arrow length is very important. If you have a modern center-shot cutaway riser bow which is already setup, finding your optimal arrow length is easy. Simply draw an arrow back to full draw and hold, while another person (safely standing to the side of course) takes a Sharpie marker and makes a mark on the arrow approximately 1" forward of the arrow rest. Then measure the arrow from the groove of the nock (like in Chapter 1) to the mark on the arrow, and you've got it. Unfortunately, this doesn't apply to everyone ... especially those with older bows or traditional bows. So let's look at this in more detail.
ARROW LENGTH MISCONCEPTIONS
Some archers believe proper arrow length should be equal to bow's draw length. This is a dangerously incorrect rule-of-thumb. In some cases, proper arrow length may equal the bow's draw length. But modern compound bows tend to require less arrow length, while older compound bows and traditional bows require more. So DO NOT assume your draw length and proper arrow length numbers directly correspond. In most cases they will not.
BOW TYPE & RISER STYLE CONSIDERATIONS
There are several factors to consider here. So we'll start with the big one - riser type (the riser is the "handle" portion of the bow). Some years ago, as traditional magnesium molded risers gave way to the production of CNC machined aluminum, we were blessed by the welcome innovation of the center-shot cutaway riser (Figure A). The center-shot cutaway riser has a much wider arrow shelf, and the center section of the riser is shifted well to the side. This allows the true center-shot of the bow (where your arrow rest should line up left and right) to be spaced far enough away from the riser's edge as to allow feathers and vanes to easily pass by the inside edge without any contact with the bow. A brilliant idea! Almost all new compound bows are now this style.
A basic molded riser (Figure B) does not have this feature. If you have an 80's or early 90's vintage bow, you almost certainly have this type of riser. In a non-cutaway bow, the actual center-shot of the bow is very close to (if not right against) the edge of the riser. This type of riser typically uses a flipper/plunger style rest mounted right against the side of the bow, where a cutaway riser generally cannot.
It is important to identify what type of bow you have. If you have a modern cutaway bow (Fig A), your proper arrow length is often less than than the bow's AMO draw length. If you have an older non-cutaway bow (Fig B), your proper arrow length will be more than the bow's AMO draw length.
CLEARANCE FOR BROADHEADS
With a traditional molded riser bow, arrows must be AT LEAST as long as the bow's draw length if you ever intend to use broadheads or other tips larger than the diameter of the arrow. Since the arrow rides along close to the riser, there isn't enough room to draw back a broadhead over the arrow shelf such that one of the blades doesn't snag on the edge of the riser as you're coming to full draw. So if you have an older bow without the benefit of a center-shot cutaway riser, choosing your arrow length is easy. In this case, we recommend you order arrows 1/2-1" longer than the bow's actual adjusted draw length. And regardless of what kind of riser you have, if you intend to shoot specialty small game hunting tips (Judo Points, Snaro's, Condor Tips, Turkey Guillotine Heads, etc.) which are unusually wide, you will definitely need arrows that are slightly longer than the bow's draw length. Even a center-shot cutaway bow doesn't have sufficient clearance to draw that type of tip beyond the outer edge of the riser.
Now, if you shoot a modern bow with a center-shot cutaway riser, the choice isn't so simple. Since a center-shot cutaway riser allows clearance for common broadheads to be drawn back beyond the outer edge of the riser, you can shoot a considerably shorter arrow. The shorter an arrow is, the lighter it will be and the faster it will fly. We'll discuss the issue of arrow weight vs. speed in much more detail in Chapter 5. But ultimately, the position of your arrow rest determines the minimum arrow length for a modern center-shot cutaway bow. In most cases, trimming your arrows 1-1.5" beyond your arrow rest will make for an ideal arrow length on your modern cutaway bow.
ARROW REST TYPE & POSITION ON CUTAWAY BOWS
Some arrow rests mount more rearward than others, permitting the use of shorter and shorter arrows. There's even a device known as an overdraw, that's specifically designed to relocate and reposition the arrow rest rearward - just so a shorter arrow can be used. However, with the increasing popularity of lightweight carbon arrow shafts, overdraws aren't really necessary any more, and are rarely used on modern hunting rigs. But some type of modern arrow rests still function much like an overdraw - locating the rest position closer to the shooter.
The diagram below illustrates how the position of the rest changes the bow's necessary arrow length. With a standard TM Hunter prong style rest, the proper arrow length is usually 1-1.5" less than the bow's draw length. With a Whisker Biscuit or similar rest which mounts just behind the riser, proper arrow length is usually 1.5-2" less than the draw length. And with a Muzzy Zero Effect or other far-rearward mounted rest, proper arrow length can be as much as 2-2.5" less than the bow's draw length. However, it should be noted that most arrow rests can be mounted and adjusted in different positions. Consider this as an estimation only.
Again, the most reliable method is to actually draw back an arrow and measure (as described above). Once your draw length is set perfectly and your arrow rest is mounted in its permanent position, determining your optimal arrow length is easy. But if you don't have a field-ready bow to measure, you can make a reasonable estimate based on the bow's draw length and type of arrow rest installed. Remember to error on the side of caution. In one way, a new arrow is like a new 2x4. One that's a little long can always be shortened - but not the reverse. Once you cut a stock length arrow, the deal is done. Custom carbon arrows are not returnable to stores. Once the arrows are trimmed to the length you specify, they're forever yours.
ARROW LENGTH EFFECTS ARROW SPINE (STIFFNESS)
Before you make up your mind about your arrow length, there's one more detail we'll need to consider. The length of your arrow is a factor in determining the proper stiffness, or spine, for your perfect arrow. The longer your arrow is, the more limber it will act when shot. The shorter your arrow is, the more stiff it will act when shot. We'll cover this issue in more detail in the next section, but you should be aware that shooting an extra long arrow often results in a double-whammy regarding arrow weight. If you shoot an excessively long arrow, not only will the excess shaft weight result in a heavier and slower flying arrow, but the added length may necessitate changing to an even heavier/stiffer arrow spine. For those of you looking to bulk-up your carbon arrows to gain a little KE (more on this later too), a little more arrow length may be a good thing. But most shooters want to get as much snap as possible out of their high performance compound bows, so keeping an eye on excess arrow weight is a big consideration.
Nitpicker's Note : We realize static spine and dynamic spine aren't the same thing. We'll get to that too. :)
CHOOSING TO TRIM YOUR OWN ARROWS
When you purchase your new set of arrows, you have two choices regarding arrow length. Most raw shafts come in stock-lengths of 32-34", so that they can be trimmed to make a proper AMO length arrow to suit virtually any bow. You may choose to receive your arrows UNCUT (full-length) OR you may receive your arrows already trimmed to length and inserted. There is no added charge for trimming and inserting your arrows, but here are a few things to consider before you decide.
Carbon arrows should only be cut with a high-speed abrasive-wheel saw. Attempting to trim your new carbon arrows with your hacksaw or your plumber's tubing cutter will result in splintered fibers and a weakened arrow shaft. Using a good quality arrow saw is best. However, with a little patience, you can get a respectable cut using your Dremel Rotary Tool with an abrasive cutting wheel attachment. So if you're the "handy" type, you may wish to order arrows full-length and trim your own. Metal inserts will still be included (but uninstalled) with full-length arrow orders.
If you would rather avoid the handyman hassle and you're already sure of your arrow length, we would be happy to professionally trim and insert your new arrows free of charge. In this case, once your arrows arrive, you'll be ready to shoot as soon as you open the box. We even include practice tips installed in every arrow. However, before you select this option, you should double-check your measurements for accuracy. Again, it's always safer to measure twice and cut once, as once your arrows are trimmed to the length you specify, they cannot be returned for an exchange or refund. However, unaltered full-length arrows, still uncut and without inserts installed can be returned.
ARROW STRAIGHTNESS AND THE ± 0.0$ FACTOR
Most carbon arrows are advertised to have a specific straightness tolerance between .001" and .006". The straighter the arrow, the more expensive they will typically be. Before we get too deep into this topic, it's worth noting that there doesn't seem to be an accepted universal method for HOW arrow straightness is measured. Per ATA/ASTM standards, arrow straightness should be measured along the full length of the shaft minus two inches. But as we understand it, this is NOT how things actually go inside the industry. On a number of occasions, we have heard arrow companies accuse each other of cheating their straightness measurements - either by measuring only short sections of their arrows, or by obtaining their straightness numbers via undisclosed measurement methodologies. If you think the bow business is cut-throat, you should witness how the arrow companies go at it behind closed doors. To avoid being shanked at the next trade show, we'll stay neutral, and assume that everyones' arrow straightness numbers are reasonably honest and comparable.
With that said, let's examine the typical straightness "classes" of arrows. Most standard-grade carbon arrows have an advertised straightness of .005-.006". These shafts are usually marketed exclusively to the hunter and beginning archers. For the purposes of big game hunting and general target use, standard-grade shafts are more than adequate. A typical human hair is about .004"-.006" in diameter. So even a basic carbon shaft of .006" straightness is quite good, and straighter than you could possibly perceive without specialized equipment.
But ... making and selling arrows is a very competitive business. So most arrow shaft manufacturers also offer a mid-grade shafts which will have an advertised straightness of around .003-.004", and "pro" grade shafts claiming a straightness of .001-.002". And as you might expect, these premium grade arrows fetch a premium price. If you're the kind of buyer who always goes for the good stuff, then by all means, buy the straightest shaft you can find. But before you shell out the green for a ±.001 shaft, there are couple things you should know.
First, the difference in a ±.006" shaft and a ±.001" shaft is more razor-thin than you might think. Carbon arrow shafts are constructed by taking very thin layers of carbon sheets and rolling them up into perfectly straight tubes (usually 6ft. long or so), much like you might roll-up a big map. Once wound, the carbon tubes are then heat-treated to bond all the layers together. When the heating process is complete and the carbon tubes cool down to room temperature, they are cut into sections (raw shafts). Some of the shafts, particularly those that come from the center of the roll, retain their ±.001" straightness while other sections distort slightly from the heating/cooling process.
As we understand it, the results vary from run to run and day to day. In most cases, even the manufacturer doesn't know how the day's crop of shafts will come out. But once the shafts are made, the manufacturer measures the straightness of each shaft and sorts them accordingly for banding and sale. One sort may be named and marketed as one arrow, another sort as something else. For example, the Beman Bowhunter ±.006" @ $64.95 p/dz and the Beman ICS Hunter ±.003" @ $89.95 are just two different sorts of the same shaft - same raw materials - same construction technique. Same is true for the popular Gold Tip Expedition ±.006", Gold Tip XT ±.003", and the Gold Tip Pro ±.001". They're literally cut from the same cloth.
Small variations in the daily manufacturing environment (humidity, pressure, air convection patterns, etc.) along with tiny deviations in the characteristics of the raw materials ultimately determines the straightness of the finished product. On one particular day, the manufacturer might yield an entire batch of ±.001" shafts, or an entire batch no better than ±.006", or even a mixed bag of straightnesses, all from the very same processes and materials. The finer tricks of the trade are carefully guarded secrets, as the art of consistently building straighter arrow shafts is literally a technical exercise in splitting hairs. But make no mistake, arrow manufacturers would rather avoid the ±.006" days. The more ±.001" days a manufacturer has, the more money they can make. Why? Because straighter shafts, whether they cost more to manufacture or not, are worth more in the marketplace. So don't be fooled into thinking that your set of $129 ±.001" pro-grade shafts are somehow fundamentally better constructed, stronger, or made from finer materials than a basic $69 a dozen ±.006" hunting shaft. In most cases, they're just a few thousandths of an inch from being the exact same product.
STRAIGHTER ARROWS SHOOT STRAIGHTER, RIGHT?
From a pure physics standpoint, yes! Arrow straightness certainly does matter. Straighter arrows undeniably fly more accurately. In long-range laboratory conditions with a mechanical shooting machine, the straightest arrows with the best spine consistencies will always group best. But try to keep this issue in reasonable perspective. You are not a mechanical shooting machine. You don't shoot in laboratory conditions, and you probably don't shoot at extreme distances (100+ yards). The straightness difference in a ±.006" arrow and a ±.001" arrow is literally the width of a single human hair. So realistically, the ±.001" arrow probably has more to do with selling arrows than shooting arrows. The truth is, only a handful of the world's archers actually have enough shooting skill to differentiate between a very good ±.003" arrow and a "pro grade" ±.001" arrow. And within the typical bowhunting range, any difference would be practically imperceptible.
Nonetheless, bowhunters tend to attribute their successes or failures to their equipment rather than to their actual skills. So owning and shooting a set of professional grade ±.001" arrows may provide some bowhunters with an edge in confidence, even if the actual technical advantage is negligible. If you're one of the many archers who believe that success is only one more purchase away, buy whatever arrows you like. Just remember that super-straight arrows won't correct poor shooting form. In the end, the benefits of a good practice regimen and proper bow tuning will FAR outweigh the benefits of shooting expensive arrow shafts.
ARE CARBON ARROWS STRAIGHTER THAN ALUMINUM?
Yes and no. While a carbon arrow's advertised specs may be no straighter than a typical aluminum shaft, carbon arrows resist distorting and "bending out of shape" much better than aluminum arrows. Though an aluminum shaft may BEGIN with a similar ±.003" straightness, its straightness quickly deteriorates through normal use and handling. So after a few months of use, your aluminum arrow set may contain a few arrows that are at original specs and some that are grossly out of straightness. Carbon arrows generally do not retain this kind of "memory" after being stressed (bent). So your carbon arrow set stays much more straight and uniform - even with heavy use. Some archers even joke that there are only two states of a carbon arrow: straight or broken, but never bent. While that's not entirely accurate, it does help to illustrate the point.
ARROW WEIGHT: GRAINS NOT GRAMS
The actual weight of your finished arrow is also very important. Arrows which are too heavy will fly too slowly and with too much loss of trajectory. Lighter arrows fly more quickly, but arrows which are too light can damage your equipment. So you'll need to know a thing or two about arrow mass and industry safety standards. How heavy should your arrows be? Well, let's start at the top.
First thing ... the weight of an arrow (as well as projectiles in most shooting sports) is customarily measured in GRAINS. Grains (gr) and grams (g) are totally different units of measure. So don't confuse them. The grain is a British system unit - based on the weight of a grain of barley. A gram is an entirely different unit of measurement. So let's just try to just forget about grams for now.
A grain is very small unit (only 1/7000th of a pound), so if you would like to have the ability to accurately weigh your own arrows, you'll need a specialized scale. You can purchase an archer's scale that's specifically calibrated in grains for under $50. However, when you order custom arrows from Hunter's Friend, your arrow set will arrive already weighed and certified by one of our professional arrow builders.
ARE LIGHTER ARROWS BETTER?
This is a hotly debated topic that we'll cover in more detail in Chapter 5. But the fact is, lighter arrows fly faster with less loss of trajectory. A faster arrow won't necessarily penetrate better, but it will make it to the target more quickly. For some bowhunters and 3D shooters, this is a great benefit. A bow that shoots very fast is often described as "shooting flat." The "flat" part is a reference to the natural rainbow-shaped parabolic flight-path that all arrows invariably take. A faster arrow travels with less perceptible arc, so it is described as shooting "flat," although "flatter" might be the more accurate word. Either way, a fast flat-shooting arrow is something many shooters seek in a bowhunting or 3D rig.
In the current archery market, speed sells. Right or wrong, it's a fact. Like in many industries, archery manufacturers are under constant pressure to make things go faster. As a result, each year brings a new bumper-crop of even lighter arrow shafts, better string materials, more efficient bow designs, friction-reducing components, etc. Again, there is some disagreement on this issue, and we'll hammer out the pro's and con's in Chapter 5, but the main idea is, lighter arrows go faster - sometimes dramatically faster. Heavy arrows go slower. So if you want your bow to shoot "flat," lightweight arrows are going to be a must.
IS THERE A LIMIT? HOW LIGHT IS TOO LIGHT?
Shooting an arrow that is too light can be dangerous, both to you and your expensive compound bow. Shooting an underweight arrow has a similar effect as dry-firing your bow. Without sufficient arrow weight, the string and limbs of your compound bow move too quickly and violently. It's like putting your car in neutral and flooring the gas pedal. The bow needs the resistance of the arrow to slow it down - so it doesn't "rev" out of control.
Of course, an underweight arrow will fly like a rocket - generating unbelievable speeds. But anyone who does this is just asking for trouble. Modern compound bows aren't toys. They generate a tremendous amount of energy and should be treated with the same respect you would give any dangerous weapon. The vast majority of serious compound bow failures are not caused by manufacturer defects, but rather by dry-firing the bow or shooting dramatically underweight arrows. For your personal safety, and the longevity of your bow, we strongly recommend you follow the IBO or AMO Standard regarding minimum arrow weight.
The International Bowhunting Organization (IBO) sets a 5 grains per pound standard that's pretty simple to follow. Arrow weight should never be less than 5X the bow's draw weight. So a 60# bow should shoot no lighter than a 300 (5 x 60) grain arrow. Simple enough! Another authority in the archery industry, the Archery Trade Association (formerly the AMO), also publishes an arrow weight recommendation chart called the AMO Minimum Arrow Weight Chart. The AMO chart is a bit more complex and takes more variables into account (brace height, bow efficiency, cam design, draw length, etc.), but it is less widely used. Some manufacturers ask you follow one standard, some the other. And depending upon your particular bow setup, the IBO and AMO recommendations may or may not be the same. Check the literature that came with your bow to find which standard you should follow.
However, since the IBO Standard applies at most 3D courses, many competitive shooters setup their arrows to weigh exactly 5 grains per pound. This keeps them just within the rules while providing the fastest possible arrow speeds. However, bowhunters usually choose arrow weights between 5 and 9 grains per pound. Later on in this guide we'll use an online arrow weight calculator to build a simulated set of arrows, so you can make sure that your arrows will be the appropriate weight for your bow before you actually order them.
ARROW WEIGHT: FISH & GAME LAWS
When carbon arrows were first introduced in the archery market, their critics (mainly competing manufacturers who didn't make carbon arrows at the time) launched anti-carbon arrow advertising campaigns to dissuade archers from giving up their heavy aluminum arrows for lightweight carbon shafts. These ad campaigns claimed carbon arrows were dangerous, they would splinter and break, they were inaccurate, wouldn't penetrate well, they would ruin your meat, they could cut your hands during field dressing, etc. Of course, as we soon learned, all that corporate blathering was a distortion of the truth - and today carbon arrows continue to command an increasingly dominant share of the hunting arrow market.
The carbon arrow concept has prevailed, but there have been casualties in the Aluminum vs. Carbon War. Several states still have hunting laws that reflect the early misconceptions about using lightweight carbon arrows for big game hunting. For examples: Washington State bowhunters must shoot arrows that weigh at least 6 grains per pound (rather than the 5 gr/lb recommended by the IBO), Alabama bowhunters must shoot at least 100 grain tips in their arrows, and Connecticut bowhunters must use arrows that weigh at least 400 grains regardless of their bow's draw weight. And while these antiquated restrictions may not exactly warrant an uprising, they are a part of each state's effort to ensure ethical bowhunting practices. So we strongly suggest you check your state regulations before ordering your hunting arrows, and respect your state's rules and regulations. And be advised that your state's rules and regulations may change from year to year. As a sportsman, it's your responsibility to know the (current) law and be sure your equipment is in compliance from season to season.
ARROW WEIGHT: MANUFACTURERS WARRANTIES
Virtually all manufacturers rate and advertise their bows' IBO SPEEDS using test arrows that weigh exactly 5 gr/lb (IBO standard). And if you want to make your bow shoot even close to it's advertised IBO speed, you have to setup the bow to shoot at or near 5 gr/lb. So it would be logical to conclude that every bow manufacturer accepts 5 gr/lb as the minimum safe arrow weight. But this isn't necessarily the case.
Look at the photo on the left. How could this 70# bow ever shoot close to it's 300 fps IBO speed if the manufacturer clearly marks the bow to require a minimum 420 grain arrow? Odd, eh? This kind of manufacturer recommendation is kind of a marketing paradox. What they're saying is, "This bow can shoot 300 fps with a 350 grain arrow ... but YOU aren't allowed to make it shoot that fast." As ridiculous as that sounds, several manufacturers pull this little fast one.
To save a few dollars in warranty repairs and to pad their liabilities should a catastrophic failure occur, a few manufacturers will sneak in a 6+ gr/lb minimum recommendation on their limb sticker or in their manual. Tricky, tricky! And some people follow it; others ignore it. But with all that said, if your bow has such a notation for heavier arrows, we suggest you contact the manufacturer to question the warranty implications before shooting arrows lighter than the official minimum. In all other cases (modern compound) a 5 gr/lb minimum is probably safe to assume.
CHAPTER 2 SUMMARY
Before moving on, you should be clear on the following:
- What type of riser does my bow have?
- Can I shoot an arrow that is SHORTER than my bow's draw length?
- Does my arrow rest function as an "overdraw", allowing the use of shorter arrows?
- What is the minimum safe arrow length I can shoot in my bow?
- What are the only proper ways to trim a carbon arrow?
- Can I return arrows which have been trimmed to length?
- What level of arrow straightness do I need?
- What is the IBO Standard regarding total arrow weight?
- What is the minimum arrow weight my bow can safely shoot?
- Does my state have any specific hunting restrictions on arrow weight?
- Does the manufacturer of my bow make any specific recommendation regarding arrow weight?