Archery/build-your-own-classic-crossbow.md

It was the "hot setup" during the Crusades... and it's going through a new revolution today.

# The Classic Crossbow: You Can Build

<img>A close-up view of a crossbow bolt.</img>

**ABOVE:** Our fieldpiece looks—and functions—like many of the more expensive manufactured crossbows. **RIGHT:** The front sight is a strap of aluminum fitted with a bead. The **BELOW** is the rear sight. **FAR BELOW:** A forward mount when the string is being drawn. FAR BELOW: This prototype has no trigger safety, but one can be added.

An archer might consider it kin to a firearm—a shooter, on the other hand, most likely would think it a stock-mounted bow... and you wouldn't need a poll to know the general public's feeling! It looks sinister enough.

In short, there's not much doubt that the modern crossbow suffers an "identity crisis," but—regardless of the mystery that still surrounds this weapon—it's becoming increasingly popular among hunters and targeters alike... and that trend hasn't gone unnoticed by MOTORS!

With such avid bowhunters on the staff, and a research department eager to take on such an interesting challenge, it wasn't too surprising to find us working on a project that we figured might be of interest to the field: designing and building a quality crossbow from scratch... testing its range, accuracy, and performance... and then comparing its performance to that of traditional recurve and compound bows.

## A QUICK ANALYSIS

The contemporary crossbow shares little beyond a basic design with its forebear, the medieval arbalest. Though both launch arrows, they differ in their construction: the former is vertically fixed to a stock, the superiority of modern materials—along with the improved lightness of modern power sources—the use of such lightweight plastic alloys, etc., have made this weapon has turned what was a crude but effective weapon of war into an admirable piece of fair-weather sport.

Over the past few years, crossbow design has received considerable attention from various manufacturers, with the result that the modern crossbow is now capable of shooting the gamut from a paramilitary-looking assault piece to an artistic expression of classical physics. And although these developments have made some models in some cases, they're beyond the ability of all but the most expert craftspeople to duplicate.

We chose the path of least resistance and used only standard components denominators in our design. The stock of our crossbow consists of a center spine covered on each side by a strengthening flange. The barrel is formed as a combination barrel (or chase in crossbow terminology), trigger housing, handgrip, and stock extension.

The bolt, or pin, is set into the nose of the foresock, and the two-piece trigger mechanism, cut from 1/4" plate steel, is pinned between the flanges at either end. The bolt seat just below the receiver. Walnut stock inserts were trimmed and shaped to mate with the stock...

<img>A close-up view of a crossbow bolt being inserted into the stock.</img>

Your Own!

on either side of the shoulder extension.
Since the string does contact the barrel and is thus subject to friction, we added a pair of shoulder extensions to our stock to reduce string wear and increase bolt velocity. Though these could also be made of walnut, we used Delrin (a Du Pont acetal resin) because of its light weight and flexibility.
Our crossbow's open sights consist simply of a front frame made of aluminum strip, and an alloy rear ring mounted to the receiver. Such a design has two advantages: each of these brackets provide sighting beads, and the rear unit can be lowered or raised as necessary to zero the piece at a specific range.

As far as aiming goes, a telescopic rifle sight is inappropriate on a crossbow for three reasons. First, the weapon's effective range is less than 50 yards or so in all but the most skilled hands. At that distance, beads and the practiced naked eye should be sufficient. Second, a fired bolt's trajectory is such that, beyond 15 or more yards, it will have traveled well past the point of impact many inches from the line of sight (see sidebar)...and since most scopes are calibrated for 100 yards, this may be restrictive or the zeroing-in process tedious. Finally, a scope narrows the field of view and adds weight as well.

You'll notice that we've noticed that our photos show two different crossbows. The first, detailed in this article, is a functional, no-gadget rendition that's not overly complicated but is still capable of being used as a fine fieldpiece or target piece. The second is a multiuse version that has some interesting features, but for the most part it's best suited to target shooting or hunting with a bow.

It sports a folding front handgrip, a removable shoulder stock extension (which allows the long arm to convert to a hand piece), and a double trigger system with an all-positive trigger safety. (This last item, by the way, can be added to our standard crossbow if desired.)

PIECE BY PIECE

You might be interested to know that we spent about $102 making our fieldpiece; that's three bolts ($3 each), one $10 1/4" aluminum flat stock (available at a scrap yard or a metals distributor); $8 in Delrin; $6 for the walnut billet; about $7 in assorted bolts; and $2 for some miscellaneous hardware--and here's the kicker--$67 worth of prod and Dacron bowstring.

Admittedly, it would have been nice if we'd been able to build our own short bow by using common materials...and believe us,

NOTE: Though we did build and test both of our crossbows, the potential for injury from any weapon is always high. This is why any whoever builds and uses this tool does so at his or her own risk.

NOSE DETAIL

<img>A close-up view of a crossbow nose detail.</img>

The takedown version is either a pistol or a long arm.

TRIGGER AND SAFETY DETAIL

<img>A close-up view of a crossbow trigger and safety detail.</img>

COCKING LEVER

<img>A close-up view of a crossbow cocking lever.</img>

(1) 1/4" x 3/4" MACHINE BOLTS

(2) 1/8" x 1/4" x 3/4" FLAT STEEL HANDLES

(3) 1/8" x 1/4" x 3/4" FLAT STEEL COLLAR

(4) 1/8" x 1/4" x 3/4" FLAT STEEL HANDLE

(5) 1/8" x 3/8" x 3/4" STEEL STRING CATCH

(6) 1/8" x 3/4" EXPANSION PINS

(7) 1/8" x 3/4" MACHINE SCREWS

(8) 1/8" x 3/4" MACHINE SCREWS

(9) 1/8" x 3/4" MACHINE SCREWS

(10) 1/8" x 3/4" MACHINE SCREWS

(11) 1/8" x 3/4" MACHINE SCREWS

(12) 1/8" x 3/4" MACHINE SCREWS

(13) 1/8" x 3/4" MACHINE SCREWS

(14) 1/8" x 3/4" MACHINE SCREWS

(15) 1/8" x 3/4" MACHINE SCREWS

(16) 1/8" x 3/4" MACHINE SCREWS

(17) 1/8" x 3/4" MACHINE SCREWS

(18) 1/8" x 3/4" MACHINE SCREWS

(19) 1/8" x 3/4" MACHINE SCREWS

(20) 1/8" x 3/4" MACHINE SCREWS

(21) 1/8" x 3/4" MACHINE SCREWS

(22) 1/8" x 3/4" MACHINE SCREWS

(23) 1/8" x 3/4" MACHINE SCREWS

(24) 1/8" x 3/4" MACHINE SCREWS

(25) 1/8" x 3/4" MACHINE SCREWS

(26) 1/8" x 3/4" MACHINE SCREWS

(27) 1/8" x 3/4" MACHINE SCREWS

(28) 1/8" x 3/4" MACHINE SCREWS

(29) 1/8" x 3/4" MACHINE SCREWS

(30) 1/8" x 3/4" MACHINE SCREWS

(31) 1/8" x 3/4" MACHINE SCREWS

(32) 1/8" x 3/4" MACHINE SCREWS

(33) 1/8" x 3/4" MACHINE SCREWS

(34) 1/8" x 3/4" MACHINE SCREWS

(35) 1/8" x 3/4" MACHINE SCREWS

(36) 1/8" x 3/4" MACHINE SCREWS

(37) 1/8" x

# The Crossbow: Fact and Fiction

Just how effective is a crossbow? To an-
swer that question, several of MOTHER's staffers took to the field with our project pro-
type equipped with a 175-pound bolt... the heavier calibre (which with a 75-pound bow weighs about 840 pounds) was also tested (a quality commercial crossbow) rated at 175 pounds... a recurve bow rated at 54 pounds, full draw (20" draw)... and a 70-pound bow rated at 36 pounds. We measured weapon range, accuracy, and penetrating power... but, ultimately, we were struck by the sheer effectiveness of the crossbow's prop niche in the ar-
mament of modern warfare.

Now we weren't interested in testing head-
to-head with the Barnett offering, and we couldn't fairly put a hand-bow against anything else. But we did want to see what we had made a series of test firings with our standard model at distances of 10, 20, 30, 40, and 50-meter marks. Each group con-
sisted of five shots fired from each barrel of our overall (126.2 grain field point) Eason 14" aluminum bolt, and the resulting patterns
were measured and recorded. The cross-
bow's ability to deliver consistent results over a wide range of velocities is a major advantage for this weapon, and a shooter's training must used to establish a direct line of sight at a given point on the target. The deviation of the points of impact from the centerline of the target was noted. Wind conditions were fairly calm throughout the test.

The chart below encapsulates our findings.
A crossbow designed to eliminate overhead costs has a respectable pattern, even out to 50 yards. (We suspect it would do the same beyond that point, but that considered expert's range.) In addition to its accuracy, the weapon's barrel would have to be drai-
ned in order to hit a target in a level line of sight... but the same situation existed in
the case of the more traditional/hand-bolt.武器. While the crossbow may not be as fast as some of the weapons we tested, since all the bolts buried themselves - some in the flitching- in the 12" of extruded polypropylene we used for our standard barrel... it does offer an effec-
tiveness in draw weights between the tradition-
al bow and the crossbow (and accounting for the standard arrow's additional mass), which is more than 125 pounds compared to overall, the ex-
tra power probably offers little, but taxes
string, bolts, and cooking convenience heav-
ily. And while it may be less expensive than being even less desirable unless it was matched with a short, light bow. Our take-home poinl
model uses a 75-pound bolt and a 6" alu-
minum barrel. A 6-1/4" compared to the larger weapon's
8-1/2" fine for targeting shooting, but not really useful for hunting.

In addition to its accuracy, string life can be extended and ball velocity increased slightly by applying a fabricative wax to the string and the barrel's shoulder sides.

As for windage control, if you want to burst a romantic balance, we'll have to conclude the facts: Although a crossbow has the advan-
tages of compactness and mechanical cock-
ing ease (it can be held at full draw without strain), it is not as accurate as a conventional bow in proficient hands... can't be loaded and fired quickly... and it doesn't even approach the overall effectiveness of a long-range rifle. In fact, it is a vital sporting tool that's slowly but surely coming into its own once again.

## FIELD TEST RESULTS

**MODEL:** TESTED: Horizontally, aluminum frame,
wristlets: Deinum shoulder slides
**PROD:** Barnett Commando, heat-pressure cured
mercury, 170-pound draw
**WEIGHT:** 1 pounds, 5-1/2 ounces

<table>
<thead>
<tr>
<td>RANGE</td>
<td>AVERAGE DROP</td>
<td>AVERAGE WINDAGE ERROR</td>
<td>PATTERN</td>
<td>NOTES</td>
</tr>
</thead>
<tbody>
<tr>
<td>10 yds.</td>
<td>e+*<br>18 yds.</td>
<td>8<br>11-1/4"</td>
<td>1/2"<br>3/4"</td>
<td>full penetration<br>zero trajectory point</td>
</tr>
<tr>
<td>30 yds.</td>
<td>17-1/4"</td>
<td>3/4"</td>
<td>-<br>light pattern</td>
</tr>
<tr>
<td>36 yds.</td>
<td>6</td>
<td>8-1/2"</td>
<td>-<br>windless bolt wobble pattern improved</td>
</tr>
<tr>
<td>40 yds.</td>
<td>2-1/2"</td>
<td>4/10"<br>8-1/2"</td>
<td>-<br>windless bolt wobble pattern improved</td>
</tr>
<tr>
<td>50 yds.</td>
<td>83%</td>
<td>8-1/2"</td>
<td>e+*<br>better pattern improvement<br>excellent penetration</td>
</tr>
</tbody>
</table>

* Zero trajectory point
† Barnett Commando comparison

<img>A diagram showing two views of a crossbow trigger assembly. The top view shows the trigger mechanism with a metal blade cutting edge. The bottom view shows the trigger mechanism with a smooth operation.</img>

TRIGGER AND SA

(continued from preceding page)
we tried! But the laminated aluminum prods
we used didn't have adequate draw
strength or the resilience to stand up re-
peated use, possibly because we weren't able
to duplicate the heat-and-pressure curing process used by Barnett International.

At any rate, we were pleased to learn that
Barnett International (1967 Gann H.W., P.O.
Box 934, Edina, FL 33596) will sell prods,
bolts, and other accessories to any-
one who orders the company's $90 postal catalog.

To ease construction, we outlined the
crossbow's major parts on graph paper
within a grid, which will allow you to make up-scaled templates for the pieces. But play it safe by matching the templates per-
fectly before cutting them out. After de-
scribing their outline... and be even more careful when actually cutting the aluminum stock, since [1] the pieces must join closely,
[2] they must fit together with no gaps left
with the file,... and [3] the center pin(s) will fit
into holes cut into both ends of each piece.
The trigger guard--should not be any thinner than .762 inches...

The best way to trim out the parts accurately,
by the way, is to use a hand saw equipped with a metal-cutting blade. Because the smooth operation of the trigger and string
smooth depends on great measure upon the per-
fect fit between these two components...
we suggest that you postpone drilling the flank pieces until you've bored your .964" post
holes according to the center points indicat-
ed on your template. When you're ready to
complete, clamp the aluminum center spin-
cer into one of the flanks and recheck the align-
ment of your template cutout from the trig-
ger housing until corresponding holes in
the other flank piece.

Overall Length: 31"
Width: 9"
Weight: 8 lbs.
Power Stroke: .964"
Sights: Open; adjustable rear post
Bolt: Exeter; 14" aluminum; .254 grams overall including .09 gram flattop

<img>A diagram showing two views of a crossbow trigger assembly. The top view shows the trigger mechanism with a metal blade cutting edge. The bottom view shows the trigger mechanism with a smooth operation.</img>

TRIGGER AND SA

<img>A diagram showing the layout of a crossbow stock with various parts labeled.</img>
**CENTER SPINE**

**FLANKS**

With that done, use No. 6 X 3/4" machine screws as temporary locating pins for the two bored components, and clamp them together in the stock. When you're satisfied that all three parts are evenly mated, drill the final member. Since the post screws are required, you'll need to operate with larger bits according to the design of the screws and nuts you've chosen.

The steel trigger components have to be painted by 1/6" of their length before being installed within the stock. Once this is done, those parts can be drilled where indicated with a 1/8" bit, and the 1/6" X 3/4" screws used to attach them. The pivot pins must be centered. The pivot pins ride in 9/64" sockets drilled into the right side, you might want to use the trigger guard to limit your course of pull so as to open up more accurately.

As we mentioned before, you can install a trigger safety mechanism according to our detailed instructions. This will help keep your safety on and prevent any accidental discharges. You can also use a small compression set-in slot cut through the central spine.

Before assembling the stock for good, you'll want to begin by inserting the trigger guard into the frame's outer edges. The rough work can be done with a grinder or file, and the metal then can be smoothed out with emery cloth. After that, you can sand down for last time after you've bored and pinned everything together and completed the cosmetic work.

The rear portion of the project includes setting the rear tang (the spring-steel leaf that holds the projectile snug against the barrel), adding the wooden (or Delrin) slide to the frame, and installing a rubber recoil cushion that insures the shooter's comfort. (These pieces can be cut to shape using the template as a guide, then rounded with a sanding block or glued to the aluminum stock prior to being finished with varnish or tung oil.)

The front sight is a piece of 1/16" X 5/8" X 1/2" steel rod bent at an angle between frames for installation within the stock. Once it's installed, it's fastened to the top of the fire stock with two No. 6 X 1/4" machine screws, and a short length of Dacron string is attached as a bead. Though we used a machined ring at the rear (to provide a housing for an experimental scope sight), you can make an external sighting point by drilling a hole through the tapping holes on top of the receiver to accept a 632 socket-head cap screw about 1/2" in length. This can then be adjusted up or down depending on whether you use a prod with a draw strength of 175 pounds ... but even if you choose a lighter bow to lengthen string life, you'll probably need some sort of adjustment. You can make one by bending four sections of 1/8" X 1/4" flat metal to create a two-wormed, bolt-together yoke that uses mechanical stops to hold it in place. A pair of slots in the stationary part of the lever hook into a 5/8" X 3" steel rod fitted into the crossbow's forestock (this should be done immediately after installing the prods). Then, another set of slots cut into the "short" jack arms catch the string. The fulcrum's just a metal collar that can be bolted back into its optimal position.

The prods are held in place by a 1/4" X 3/4" X 1/4" block of aluminum faced with a strip of hard rubber. The rubber provides additional cushioning, and the metal block is fixed tightly against the bow's face by a 1/4" X 3/4" cap screw threaded into a tapped hole at the nose of the stock.

Once the prods are installed, you'll have the pleasure of stringing it. First, you'll need what's called a buster string along with the regular Dacron cable. This set of strands is too long than service strings and thus can be slipped onto the prods and tied off at each end. Then, take your bows back to the cocked position so real string can be looped in place. When that's done, both strings can be released with the trigger guard being pulled back slightly so as to simulate in which case it should be "dry fired," since that practice can split the prods.

It should be obvious that your fini shing job has a lethal potential and should be handled with the same caution that you'd give to any longbow or firearm. Don't load it until you're ready to shoot it because you could find yourself in field behind your target get to safely absorb any overshots. Too if you're interested in exploring the crossbow's capabilities further, check out these links below before you buy it - it could save you lots of money later. Meanwhile, you might want to look over our other subtopics concerning this article to see what kind of information would expect from your modern-day archer!

**EDITOR'S NOTE:** If you're interested in making this project featured here (or smaller take-down version) but would prefer detailed step-by-step instructions, a set of building plans, or even an actual kit available at a cost of $10 plus $1.00 for shipping and handling from Mather's Planes, Crossbows, P.O. Box A East Flat Rock, NC 28726.

<page_number>9</page_number>

CENTER SPINE

TRIGGER AND SAFETY COMPONENTS

FLANKS

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