Ruminations on Archery Ammunition: Once, not too long ago, in the annals of firearms history there was a group of “experts” who proclaimed “No one can reasonably expect to hit a single man at 100 yards with a gun on the first shot.” Of course, the men who proclaimed such idiocy had never considered the idea of a rifled barrel or aerodynamically shaped projectiles. In the quest for the ultimate in accuracy and long range performance, most firearms manufacturers now focus on tightly controlled land and groove diameters, consistent barrel profiles, bore finish, action bedding and good muzzle crowning. Projectile manufacturers concentrate on jacket/core concentricity, weight and shape quality controls. In the firearms world, it is widely recognized that projectile spin rates dramatically affect accuracy. Spin rates, depending on the weight, length and velocity of the projectile, have been categorized thoroughly. That fact lays in firearms manufacturers standardizing barrel twist rates for the most commonly used projectile weight in any given caliber using standard velocities. Applying this hard-won knowledge to archery only makes sense to me. Why do we not see published charts with columns containing arrow weight, launch speed and optimum fletching offset or helical twist? It continually astonishes me when I hear or read an otherwise knowledgeable archer make a statement like “you are not a shooting machine” or “you will never notice the difference” or “there is no such thing as perfect arrow flight” when discussing arrow straightness or fletching twist rates. It also strikes me as strange how those same folks will rush to a Hooter Shooter and go to the trouble of “tuning” arrows by rotating nocks to achieve the best groups possible and ignore the evidence of what they are attempting to work around…“spline”. In this case, spline being defined as a line extending the length of the shaft, usually a material over-lap construction defect occurring during shaft manufacture that makes one side of the arrow stiffer than other locations around the shaft circumference. If our archer is determining shaft spline location he is attempting to apply a “solution” or “work-around” to a manufacturing problem within the shaft. I submit that if a group of shafts exhibit spline location preferences when grouping at 20 yards, the existence of that spine or hard lengthwise portion of the shaft of necessity implies imperfect wall concentricity and/or density. The stiffer portion of the wall must, by definition, be heavier than other portions of the shaft. Therefore, these heavy, lengthwise internal phenomena must negatively impact in flight rotational stability. That instability will most probably not be compensated for by the action of fletching. I would presume that given enough tail drag and spin even the most poorly constructed arrow shaft will fly to “acceptable” accuracy standards at twenty or so yards. If, in the world of firearms projectile industry, jacket and core concentricity were not important, why would there be so much attention focused in that area? If one compares time-of-flight to the target at 100 meters between a round leaving the venerable 30-06 and an arrow launched from a 70 pound draw compound bow, the arrow has a much greater opportunity to be negatively impacted by this type of inconsistency. I submit these built-in irregularities are the primary cause of poor long range accuracy in modern archery ammunition. If one accepts the realities of the existence of spline in most carbon arrow manufacturing processes, one must also accept that the measurement of spine (the resistance of a shaft to flexing) on any given arrow of this type could only be taken as an average of measurements around that shaft and it is a far less than a perfect way to categorize the stiffness of a set of shafts. I would also beg to differ with some folks’ opinion that static spine and dynamic spine “have nothing to do with one another”. To the uninformed a statement like this is obfuscation at its worst. To the informed, the opinion is ludicrous. It is well known that information regarding the dynamic properties of a given material can readily be extrapolated from static testing. It may be true that complete understanding of stress fatigue failures can only be obtained through dynamic testing but data collected from static testing is well proven to be an excellent guide in selecting suitable materials for any given application. This all leads me back to “You’ll never know the difference.” Really??? Today, folks with firearms make successful hits on very small targets at ranges exceeding one mile. It was only a few years ago that some thought it impossible to hit those same targets reliably at 100 yards. In this era of highly advertised, very profitable carbon composite arrow shaft construction, I wonder how so many otherwise intelligent archers ignore the virtually perfect lack of spline in modern aluminum alloy arrow shafts. Are archers as a group so easily stampeded by advertising into the “latest and greatest” craze? It would appear to be so. How is it that only one company can make the claim that their archery ammunition products have won EVERY Olympic medal in modern history and the basis of those victories is rooted in a super consistent alloy tube? I also wonder why, in an age of chronographs, high speed videography, personal computers and spread sheets; we still have no reliable data regarding weight, length, speed and rotational velocities of arrow projectiles and how best to stabilize them? For you folks shooting wood, remember, God loves you too!
interesting concept, but . . . I believe the answer is "variables". A manufactured bullet is loaded into a cartridge case with no variables thus making the flight predictable at a given speed. You have no spine to deal with, no length variables, no vane variables, or tip/broadhead variables. Each Firearm bullet is the same for all intents and purposes. While I'm sure that a complex algorithm could be produced to capture many of the arrows variables, it would be quite complex. Sometimes efficiency begs for the ol'trial & error method. Even with the advanced bullet ballistics calculators available today, you still work up a load by putting some bullets into a target. I am well versed in firearms ballistics, but am new to archery.
These are two of many terms used in the description of arrow properties. “Spline” is the term (originating during the widespread use of wooden shafting) that describes the stiffest side of the shaft (usually a grain orientation). “Spine” is the term coined by Easton Technical referring to the deflection, in thousandths of an inch, of a shaft when suspended between two points and a specific weight is hung in the middle. The points holding the shaft are 28 inches apart and the weight being 1.94 pounds (31 ounces). Nice photo though!
Got one of those word checker things in my Smart Phone (oxymoron), the thing really torques me sometimes.
I appreciate your thoughts on working up a load for your firearms; however, projectile weights, lengths, launch velocities and twist rates are all part of the equation making the difference between a two inch group at 100 yards and a load printing a one inch group at 200 yards. There are great numbers of variables in hand crafting ammunition for a firearm. Just case variables alone include case wall thickness, concentricity, neck length, sizing die diameter, primer pocket depth, flash hole position and cleanliness, brass hardness and manufacturer choice (brass composition). The quantity of data may seem overwhelming but that is what the study of maximum accuracy potential is all about…sorting out that which doesn’t work. So much of the archery industry is obscured by myth, legend and a predominant concept that quantifying the information is impossible. The other oft repeated mantra goes something like “You’ll never know the difference.” I find it hard to swallow that the same approach used with firearms should/could not be applied to archery. I would not be surprised to learn that great amounts have time have already been invested in the pursuit…but the data is closely guarded. If you were given the clear choice of an archery ammunition combination that would reliably group one inch at twenty yards and another that you had to struggle with to keep under three inches, which combination would you choose? Stupid question, huh? My main point is that at one time the consensus of the “scientific” intelligencia was the Earth was flat. Then a crack-pot bone-head ignored popular opinion and proved them wrong. I am by no means Columbus; however, I am a bit bone-headed. I know because my mother told me so. It would just be nice for people to apply a little more brain power to cantilever spring powered projectiles. Oh, and a more appropriate description of the photo contributed by Mr. James would be “male splined (plural) shaft”.
Konrad, "sorting out that which doesn’t work". At what speed? Fletched with what? Tipped with what? At what spine and of what material? "I find it hard to swallow that the same approach used with firearms should/could not be applied to archery". What firearms approach do you refer to? I know of no data that produces the " clear choice" you refer too. I like the way you think, Challenge everything.
I submit that a starting point would be a specified launch velocity, arrow weight, sectional density, and spine selected by a manufacturer of repute with a combo-point (the most aerodynamic field type tip). Marking the shaft in the fashion seen in old rocket testing film and applying varying degrees of offset and measuring the rotational velocities imparted to our “standard” shaft with the use of high speed video would also be a start in quantifying the effects of angle of offset and fletching type. Measuring and recording the groups produced at a range of fifty yards (a range which most diligent archers can attain a good level of proficiency) and comparing those groups with changes made to ONE component or variation at a time will lead to repeatable results and conclusions regarding those changes. Perhaps, the launch device could even be an adjustable pneumatic type similar to that of a typical aircraft catapult thereby able to duplicate differing types of cam, cantilever spring (limb) and riser designs. This type of device would also eliminate rest and release variables. Just because quantifiable data is not easy or quick to come by would not make the endeavor impossible (or any less fun).
I'm still dealing with the difference between aluminum and composite shafts. I'm told that aluminum bends so its no good but the other guys say that carbon breaks and will put your eye out. RC
As with so many things in life, there are compromises with either material. Easton (the brand I choose) makes an extremely consistent alloy product. There is virtually no spline in new shafts; however, dents can weaken aluminum tubing and glancing blows can bend them as well. I am of the opinion that attempting to straighten alloy shafts work hardens one area of the shaft wall and thereby imparts spline to the shaft. This makes that particular shaft react differently than others in your quiver. I scavenge the inserts, uni-bushings and nocks and break the bent shaft so there is no confusion If you take care of your alloy shafts, the aluminum will tend to work harden on its own just from the flexion caused during normal shooting. The spine, given enough shooting…i.e. thousands of times will tend to drift upwards. This in and of itself is not that big of an issue for the average archer but may effect long range accuracy. Incidentally, Easton guarantees the straightness of their Super Slam XX-78 shafts for two years with normal use. Of course this does not include impact damage or poor technique extracting your arrows from the target. The primary sales objection heard with our current speed-crazed industry is in the weight of alloy shafting. Here is where I point out the not so coincidental new trend in carbon composite shaft manufacturers’ general increase in the grains per inch of many hunting shafts. A primary benefit of carbon composite shafting is manufacturers’ ability to produce a shaft of proper spine, decent weight and straightness AND small diameter. Small diameter produces lower drag both in the air and when penetrating targets. Carbon’s deficits are high price, poor wall concentricity (i.e. spline) and straightness. Facts that all carbon composite shooting archers need to know are: A: The binding material (essentially an epoxy compound) degrades when exposed to heat over 300 degrees Fahrenheit and weakens the shaft. B: While a composite shaft will try to return to its original shape after glancing blows or hard impact, fractures in the binding agent and/or the fibers themselves can produce conditions potentially dangerous conditions for the shooter and those nearby. Easton Technical suggests careful inspection of each composite shaft prior to EVERY shot by twisting and listening for cracking sounds. I have also found that cleaning each shaft with a couple of strokes from a hand towel quickly reveals cracking and splintering as those splinters will catch the threads of the cloth. In my opinion, perhaps the best of both worlds is the alloy shaft with carbon composite sheathing but…did I mention the price??? In any of the cases outlined above, careful inspection and discarding suspects immediately is the best approach. Just be aware of each construction methods’ benefits and limitations when choosing your ammo. You will be safe if you follow the manufacturer’s spine suggestions for your draw weight, length and point weight. It is your responsibility to inspect and discard any rounds that are damaged. I hope this discussion helps a little. K
