ARROW LETHALITY
Part
III: Turning "Hits" into "Kills"
BY
Dr. Ed Ashby
The hit looked good. After a short wait, the blind was abandoned
and the blood trail located. Drop by
drop the trail was followed, but the trophy was never found.
For the last thirty‑eight
years I have bowhunted big game. I have
heard countless versions of this scenario.
Sadly, it is more common now than when I first started. In Part II of this series we examined some
of the results of the Natal Study. In
Part III we will look at the development of much of today's equipment in a
historical perspective framed by the information from the Study.
Some of the information
presented here is a summary of information presented Part II. Here it is presented in a more 'readable'
form, without the technical supporting data.
The selection of the
broadhead and arrow one hunts with is the key 'secret' in converting hits into
kills. Next to hunting skills, it is
the biggest determinant of bowhunting success.
When I began bowhunting,
there were only a few commercial broadheads.
All were rigid broadheads, based on designs centuries old. The majority were single blade heads. Some were small three-blade heads. Few were of other designs.
Only a handful of
contemporary bowhunters had ever taken 'big' animals. Pope and Young had taken Grizzly and Brown Bear, Lion and Cape
Buffalo. Howard Hill had taken an
impressive array, including Elk, Moose, Bears, Bison, Lion, Leopard, Cape
Buffalo, and Elephant. Bob Sweinhart
took all of Africa's big five.
Soon, Ben Pearson took a
Polar Bear. Fred Bear took Brown and
Polar Bear. Then Fred ventured to
Africa, taking Lion, Cape Buffalo and Elephant.
All of these hunters,
except Fred, had used conventional single blade broadheads. Fred used his original
"Razorhead." It was a single
blade head but with a small 'bleeder blade' insert. The bleeder blade was made of a hard, brittle, carbon steel,
similar to the old 'blue steel' razor blades, hence the name.
Fred often said, "The
purpose of the bleeder blade is to open a larger hole in the skin on
entrance. It's designed to break on
impact with any firm resistance. The
main blade carries on, working like any other broadhead."
Fred felt that opening a
large entrance hole reduced the drag on the arrow shaft, giving better
penetration. He felt it also gave a
better blood trail. The purpose of the
bleeder blade was not to increase the cut area of the broadhead, not to make it
a 'multiblade' broadhead.
Still, the Razorhead was
responsible for ushering in a whole new era in broadhead design. The multiblade broadhead.
They were touted as
offering 'increased cutting area'. They
did cut a larger hole, but the increased tissue resistance of the multiple
blades resulted in less penetration.
The rigid multiblade head
was closely followed by the 'replaceable blade head'. These featured multiple blades of thin stainless steel, attached
to a steel, alloy, nylon or polymer resin 'body'.
Their blades were
designed, not to shatter, but to remain intact. They were to be replaced after each shot, negating the need to
resharpen. Like their rigid
predecessors, they offered increased cut area, but at the cost of increased
tissue resistance.
It soon became difficult
to find quality single blade broadheads.
Ben Pearson's fine Deadhead fell by the wayside. Only the Black Diamond and the Howard Hill
broadhead could be located in archery suppliers inventory.
I, and many others, soon
discovered that no multiblade broadhead
penetrated bone well. The
resistance was simply too great.
The replaceable blade
models often broke when bone was hit.
Even when they did penetrate, they tended to bend, often shedding blades
in the process. Blades which survived
were nicked, bent and severely dulled.
The thin blades were often damaged even when no bone was hit.
Concurrent with the
arrival and wide spread use of these broadheads, numerous researchers noted an
increase in the number of animals being hit and not killed. But these broadheads were not the only factor
contributing to the increase in lost animals.
Coinciding with their
proliferation was the development of the compound bow. It's contribution to wounding was not a
direct result of its design but was simply a bi-product.
The compound bow's 'let off'
produced a less violent thrust to the arrow shaft. Compound shooters soon discovered that lighter arrows could be
used with the compound bow.
The lighter arrows
resulted in increased arrow speed and flatter trajectory. The flatter trajectory made it easier to hit
an animal. But the lighter arrows
caused a loss of momentum. This reduced
penetration.
I have no intent to
degrade the compound bow. It is an
engineering marvel, capable of transmitting more energy to an arrow, of a given
weight, than any equivalent conventional bow.
It has opened the joys of bowhunting to many who are not able to learn
to shoot a conventional bow of adequate weight for big game hunting.
The problem came in the
misuse of the compound bow's available energy.
Instead of using the extra energy for increased arrow momentum, many
bowhunters chose to use lighter arrows in order to get higher arrow speeds.
Speed was in vogue. Arrow shaft materials became ever
lighter. Broadhead manufacturers made
ever lighter, and more fragile, broadheads.
The use of thin replaceable blades became the norm.
In the search for even
more speed, overdraw bows became common in the hunting field. They made it possible to use shorter, still
lighter, arrows. Some as light as 300
grains were being used.
Arrow momentum was
drastically reduced. Combined with the
tissue resistance to the multiple blades, penetration was greatly reduced, and
wounding became a common occurrence.
Lets now look again at the
facts which emerged from the study of killing and non-killing hits on real
animals in the Natal Study. The
facts are: There is a direct correlation between the depth of arrow
penetration and percentage of killing hits.
The deeper an arrow penetrates, the more likely it is to kill. There is no correlation between
broadhead size, number of blades or 'cut area' and the percentage of killing
hits.
Given a well placed
hit with a sharp broadhead, broadhead failure and inadequate penetration are
the only two things which cause failure to kill.
Broadheads must
remain undamaged. Many broadheads are
fragile, bending or breaking on impact with even light bone. A rigid single blade broadhead is the least
likely to be bent or broken. A broadhead
which is damaged gives inadequate performance.
It frequently fails to penetrate well.
It frequently fails to kill.
Replaceable blade heads
are four times more likely to be damaged than a rigid single blade
head. Rigid multiblade heads are over three
times more likely to be damaged than rigid single blade heads.
Single blade heads
penetrate both soft tissues and bone better then any multiblade head. This holds
true regardless of the presence or absence of any 'bone breaker' tip.
When a bone is hit, heads
with four, or five, blades penetrate better than heads with three blades. Where only soft tissue is hit, three-blade
heads out-penetrate those with four, or more, blades. Neither penetrates as well as a single blade head.
Single blade broadheads
hitting the spine have a 'kill rate' of over 80 percent. Multiblade heads, whether replaceable blade
or rigid, scored a 0 percent kill rate for spine hits. (There were roughly an equal number of spine
hits with each type of broadhead).
When a rib is hit on
entrance, a single blade broadhead is three times more likely to kill than a
three‑blade head. It is twice as
likely to kill as a head with four, or more, blades. On a broadside shot hitting the shoulder blade, a single blade
head is three times more likely to kill than any multiblade head.
Single blade broadheads
are more than twice as likely to produce an exit wound as a multiblade
broadhead. This results in a better
blood trail, particularly if the entrance wound is high, as in a shot taken
from a tree stand.
When a sharp
broadhead remains intact on a well placed hit, failure to kill is due to
inadequate arrow penetration. Taking all hit placements, arrows with
single blade heads average 41 percent more penetration than three blade heads
and 34 percent more than four blade heads.
Those are the hard,
cold, facts. They are actual
measurements from a large number of hits on real animals.
Good single blade
broadheads out-perform multiblade heads under all conditions. Well, there is one possible exception: a gut
shot. I say 'possible' because I simply
don't have enough data on gut shots to say for sure.
Fortunately, there has
been a resurgence in 'traditional' archery in the last decade. A number of major manufactures now feature
traditional equipment in their product lines.
With this renewed interest
in traditional archery came a revival of the single blade broadhead. Along with the Black Diamond and the Hill
broadhead, both of which never ceased production, there are now many others
available. Some of the finest single
blade broadheads ever made are available to today's bowhunter.
Just what is a 'good'
single blade broadhead? I have several
criteria. The blade must have
reasonable metal thickness. It must be
of good quality steel, neither bending nor breaking when hard bone in
hit.
I prefer carbon steel with
a Rockwell hardness from forty‑nine to fifty‑five. It is still sharpenable with file or
stone. It will break before it will
bend and, if of reasonable thickness, it's awfully hard to break.
I prefer a broadhead which
is long and narrow in shape. Both Hill
and Sweinhart felt that a single blade broadhead 3" long and 1" wide
offered the best penetration. Pope and
Young used heads of similar dimensions.
The longer the cutting
blade for any given width, the better, so long as rigidity of the head is
maintained. As we shall see in Part IV,
the ratio of length to width is important in using arrow momentum for maximum
penetration.
The ferrule should taper
long and smooth into the blade, with no abrupt junctures. Just as with the blade, the longer the
ferrule's taper, the better it uses arrow momentum, and the deeper it
penetrates.
My favorite broadhead is
the 190 grain Grizzly. I routinely narrow these to 1" (or less) cut
width. The length is left at three and
one-quarter inches.
Next to broadhead
design, total arrow weight and shaft diameter are the most important features
in penetration. Pope and Young recommended ten grains of
arrow weight for each pound of bow draw weight. For the heavy bows they used, they weren't far off.
The figures on arrow
weight are less conclusive than for broadheads. It is difficult to get enough facts to reach definite
answers. To be valid, all the shots
must use the same broadhead, shaft diameter and momentum, but be with arrows of
different weight.
What information is
available suggest that minimum arrow weight should be at least 650
grains for 'standard' big game animals.
With a strong broadhead, this normally gives enough penetration
when bone is hit.
My standard hunting arrow
is 785 grains. The shafts are of
compressed cedar. I have nothing
against the more modern shaft materials.
They just don't have sufficient spine and weight in a shaft diameter as
small as I want, and I will get to shaft diameter in a moment.
I can get the desired
weight, stiffness and diameter with 'modern' shaft materials by using double,
or triple, shafts (one shaft inside another).
It is a device I have used when making 'super heavy' arrows for the
biggest of animals.
On the truly big animals,
I find that an arrow weight of 900+ grains is required, with a small diameter
shaft, to consistently get enough penetration. This, even when using modified broadheads and conventional
bows from ninety to well over a hundred pounds draw weight.
Shaft diameter is the
other important factor in penetration.
When broadhead and momentum are equal, a shaft larger than the broadhead
ferrule gives 33 percent less penetration than one equaling the ferrule's
diameter. It will penetrate 40 percent
less than one with a shaft smaller than the broadhead ferrule. My shafts are slightly smaller in diameter
than the ferrule of the broadheads I use.
So how can you judge if
your broadheads and hunting arrows give adequate performance? Here are two 'test' I can recommend. They apply to all animals up to, but not
including, the 'super big'. Every
reliable killing combination I have tested could pass them.
(1) You should consistently
get total penetration on broadside chest shots (an exit wound). (2) Your arrows should be able to consistently
penetrate through the shoulder blade and several inches into the thorax, with
broadhead undamaged.
Broadheads and arrows for
the 'super big' animals are an entirely different subject, as is hunting
them. For what it is worth, my goal on
BIG animals is consistent penetration to the fletching on chest shots, with broadheads
remaining undamaged.
If you want to turn your
hits into kills, my advice is:
Use any bow you like, compound, recurve or longbow. Hunt with the heaviest draw weight bow you
can handle (and 'handle' is the key word here).
Select a quality
single blade broadhead of a long and narrow shape. Mount it on as heavy a shaft, of as small a diameter, as your bow
will shoot with reasonable trajectory.
As we shall see in Part IV: The Physics of Arrow Penetration, extra
arrow mass does a lot to offset lower bow draw weight or arrow velocity.
Use a minimum of
650 grains total arrow weight for most big animals and 900 grains if after the
'super big' animals. Don't worry about
arrow speed. Practice until you can
place your arrows in the 'kill zone' at the range you intend to shoot.
Study your quarry's habits
and practice your hunting skills. The
heavier arrows do cost you some 'range'.
Get close to your game before shooting.
Get your broadheads really sharp.
That, in total, is my
personal formula. It usually
results in finding the quarry, quiet dead, at the end of a rather short blood
trail. Is it 100 percent
effective? Almost. Out of several hundred animals hit with such
an arrow and broadhead, only two failed to end up hanging in my camp.
One was a Minnesota black
bear. Within 20 yards of where it was
hit, it plunged over a steep bank and into a dense cedar swamp with chest deep
water. I never located him.
The other was a mule
deer. The blood trail ended, just five
feet from a 'Jeep trail', in a puddle of blood, a 'body print', tire tracks and
human foot prints. He ended up in
someone else's freezer!
In the next installment of
this series we will examine the physical laws which govern arrow penetration, assuming
one uses those good broadheads that will remain undamaged!
Copyright 1996, Ed Ashby