ACS Bow Testing

Shooting the ACS CX Longbow

By Dr. Ed Ashby

Roswell, New Mexico. UFO enthusiast world wide will recognize the name and location. They regard the purported crash of an alien spacecraft near Roswell as one on the major events; and major government ‘cover-ups’; in the annals of alien lore. Was alien technology literally dropped to earth in the high desert country near Roswell, NM, on that hot summer’s night in 1947? I think I may be beginning to wonder if it is true!

What has brought about this questioning? Well, it has to do with a bow. Not just any bow. One of O. L. Adcock’s ACS CX bows. Recently, I’ve had the privilege of doing a respectable amount of shooting with the first of O. L.’s ACS longbows to make its way to Australia. Though it is not my bow, I did manage, not too easily I might add, to convince Cher to allow me to borrow it for a few test shots. (And it did take more than a little convincing to let me test “her bow”.)

In case one fails to see the connection between the ACS CX and the crash of an alien space craft, O. L. Adcock hails from no less than Roswell, New Mexico. I might add that what I found in the ACS CX does, truly, appear to be out of this world. Let me explain.

This narrative is not intended to be a ‘bow performance report’. That has previously been done – and the ACS limb design was found to be an almost unbelievable performer, in terms of its mechanical efficiency. It outperformed most every recurve bow previously tested, not to even mention other longbows. Its mechanical efficiency (how well it transferred the energy stored in its drawn limbs to the arrow) even equaled that of many of the modern compound bows.

This report is about the experience of shooting an ACS CX. The time I spent with the ACS CX was far from a definitive test, in the engineering sense of the term. What I was most interested in was its ‘shootability’, especially under field conditions.

Yes, I did look at the draw force curve, and it is as uniform as I have ever seen in a bow. The draw is as sweet and smooth as a bow gets. But … there is more to a hunting bow than just numbers.

First, a bit about the nomenclature. The ACS stands for “Adcock Cross Section”, and is the term that O. L. has applied to his extraordinary bow limb design, which I’ll describe in more detail later. The CX stands for “Carbon Extreme”, because the limbs utilize carbon fiber facing and backing. It is, however, neither the facing and backing material nor the limb’s core materials which, in large measure, sets the ACS CX’s performance apart from other bows. It is the limb’s design; the Adcock Cross Section.

From a bowhunter’s perspective, I found the performance level of the ACS CX staggering. On the bow I tested, I draw only 55 pounds, at my 27″ draw. As most will know, after a quarter century of intensive field testing of terminal hunting arrow performance, I have become convinced of the many virtues of hunting with an arrow of high mass.

I did my shooting test of the ACS CX with a set of six heavy hickory arrows, of a tapered profile. With 160 grain field points, the set of six arrows averaged a mass weight of 782 grains. These arrows are of the same mass weight as those I normally use off my 70 pound draw weight longbow.

After shooting several groups at 20 meters (a distance I consider to be my maximum hunting range), from numerous ‘hunting positions’, using both the ACS CX and my 70 pound longbow, the next test I did was to do some shooting at a 40 meter target. I was literally astounded when the ACS CX appeared to be shooting substantially flatter at 40 meters, with the heavy arrows, than was my 70 pound longbow.

After rolling a few of the arrows across the Ohler 35P chronograph I could see why! The ACS CX, at only 55 pound draw weight, averaged a 4 feet per second faster launch velocity than did my 70 pound longbow! The particular 70 pound longbow I was testing against is a ‘modern’ longbow, slightly reflexed and deflexed, with Tonkin Cane core and fiberglass facing and backing.

Though the level of performance of the ACS CX bow is truly outstanding for a longbow of 55 pound draw weight, it was not that which impressed me the most. What I was most impressed with was the fact that, even though it has very slender, thin limbs; I could shoot well with it!

A very pragmatic bowhunter; that’s how I think of myself. Yes, there are qualities I look for in my hunting bows, but I’m not wrapped up in the bow; neither its looks nor the arrow speed it can generate. For me, the bow’s purpose is to deliver the hunting arrow. I want it to do that with a monotonous regularity, under the full variety of hunting conditions; while requiring as little from me as possible. I use longbows, recurves and compound bows in my studies, and I am anything but a ‘bow freak’.

Handling characteristics, things often intangible, are for more important to me than the raw energy output potential of a hunting bow. I have always been blessed with the ability to go up in bow draw weight to make up for any lack of mechanical efficiency in my bows.

In a ‘serious hunting bow’ I value quietness and handling ease. There must also be a smoothness of draw that gives a fluid feeling; a feeling which makes a rapid shot, or ones at moving targets, feel totally ‘natural’. Hand shock must be negligible, so that follow through does not feel interrupted; and the bow must “fit me”, and fit with all the nuances of a custom fitted double rifle or shotgun. But the one thing I must have in my hunting bow, above all else, is “forgiveness”.

I shoot a bow a lot, and have been shooting them for near a half century, yet I have what must, surely, be one of the world’s worse finger releases. This is an affliction that, during my early years of bowhunting, I struggled fiercely with. It was Ben Pearson who first showed me a solution that worked for me.

Ben’s cure was simple, direct and effective. He told me to work up to a heavier draw weight bow; one having a long overall bow length; and to shoot a bow whose limbs had a high mass, especially towards the limb’s tips.

The longer length makes the string angle less acute when the bow is drawn, and the ‘finger pinch’ is less. This helps reduce the tendency to drag a finger off the string. High limb mass, and especially mass towards the tips, does, however, result in some loss in a bow’s mechanical efficiency. The lower mechanical efficiency requires that, to get equal arrow speed with a bow of that design, one must use a significantly higher level of draw weight, but this bow design makes the limbs very stiff; very difficult to ‘twist’, or, more precisely, to flex, laterally.

The logic behind Ben’s cure was precise. The higher ‘holding weight’ of the high poundage traditional bows tends to literally rip the string from one’s fingers, minimizing the amount of string and limb torque caused by a poor release. High mass in the bow’s limbs gave them the strength to recover from a poor release, literally forcing the string back into alignment with the arrow quickly when the bowstring is released. The somewhat slower forward movement of the higher mass bow limbs also provides slightly more time for the string to recover from the influence(s) of a poor release, before the arrow leaves the string. All these elements work in accord to negate the effects of a poor release on the arrow’s flight.

The final element in Ben’s recommendation was follow-through. Forget about the bad release. Use a bow design that helps counter and correct the bad release’s effects and then concentrate on developing a good follow-through. In other words, stay on target until the bow has had time enough to correct for the bad release and the arrow has left the bow.

The solution worked very well and, through the years, I came to prefer that all my serious hunting bows have limbs that are narrow and thick. Under the pressures of a hunting situation it is often difficult to do everything ‘textbook’. There is no doubt in my mind that forgiveness in my hunting bows has, in many instances, turned what would have otherwise been a marginal, or even miserably deficient, shot into one that was more than “close enough to kill”.

In my many field studies, of necessity, I am forced to use a wide variety of bows. It has been a consistent experience that I can not, due to my poor release, shoot any bow with a holding draw weight much below 70 pounds very accurately, ‘off the fingers’ (and this, along with their acute string angle, is the reason that I cannot shoot compounds accurately with a finger release, and am forced to use a release aid). It was my meeting with the ACS CX that has now called this preconception of mine into question.

The ACS CX has very thin, light and quick limbs. Unlike any other ‘mid draw weight’ bow, possessing those design features, that I have ever shot before, I found that I could shoot this 55 pound bow at least as accurately, if not slightly more so, under field conditions, as I could any of my heavier draw weight bows, from 70 pounds on up.

The reason for this is the, somewhat radical and revolutionary, constantly changing radius of curvature of the ACS CX’s limb design. In cross-sectional profile, the limbs have an arch to them, with the limb’s facing being concave and the backing being convex. The degree of arch increases progressively as it approaches the limb’s tips. This arched cross-sectional configuration of the limbs markedly increases their rigidity, both longitudinally and laterally, without adding anything at all to the mass of the limbs.

The design of the ACS CX’s limbs makes them very stiff towards the limb tips. All else being equal, having stiffer limb tips translates into higher bow performance.

The only flaw I could find at all about this particular bow it is that the grip did not fit me well. Rather understandable. Cher’s hand span is only slightly more than half as great as mine!

Is the ACS CX truly revolutionary? Is it the natural progression of man’s technology, a result of new materials and applications? Or … could it just possibly be … that they really do incorporate extraterrestrial technology? I’m not even certain that I want to know the answer to that question, but, as all the bows I’ve ever owned have had female personalities – and female names – if I ever do get an ACS CX of my own, I think I might just have to name it ‘Venus’; or, perhaps, after one of the ‘alien’ female Star Trek characters!

It has been a long, long, long time since I truly lusted for a bow; but the ACS CX? The thought of using a bow with a 15 to 20 pound lighter draw weight; possessing all the shooting and handling qualities I so value in a hunting bow; and that would still produce the tried and proven, devastatingly effective, arrow momentum levels of Lady, my much loved 94 pound longbow with which I’ve taken well over 300 big game animals, worldwide? I’m beginning to fear that I might just have to plead guilty!