WARNING This should be treated with the same level of respect you would give to any other firearm. Please keep this and all firearms stored securely away from children.
DISCLAIMER This book in no way condones illegal activity! It is your responsibility to determine the legality of your actions. I have no control over the workmanship, materials, tools, methods, or testing procedures employed; so I hereby disclaim any responsibility for consequences resulting from the fabrication of any item described in this book. I cannot and will not accept any responsibility for this information and its subsequent use. This book is sold for informational purposes only!
© 2010 by HMT, LLC all rights reserved
TABLE OF CONTENTS Section 22 Caliber Revolver The 22 Rim Fire About the gun Simplicity Ammunition Instructions Disassembled view of all components Bill of Materials Minimum tools required Using calipers to precisely layout hole locations The Cylinder Cylinder Scribing Pattern Center drilling & drilling cylinder The Frame Firing Pin Hammer Assembly Handle Brass Handle Template Setting the timing on the cylinder Spring Anchor Screw Testing Adjusting the firing pin Accuracy Handling Technique Appendix A –Milling Coordinates Cylinder Drawing Frame Base Drawing Front Yolk Drawing Rear Yolk Drawing Hammer Drawing Supplemental
Page 3 3 3 3 4 5 5 6 7 8 9 9 10 11 13 13 14 14 15 16 17 17 17 18 18 19 20 21 22 22 23
Page 2 of 23
22 CALIBER REVOLVER The purpose of these instructions is for the average person, with average skills and equipment, to construct a simple 22-caliber revolver. I have read a lot of books on how to make homemade guns and what I have found is that there are two extremes. At one end of the spectrum, you have the crudely made single shots that are impractical and more dangerous to the person firing the gun than to their target. At the other end, you have complex guns, like semi and fully automatics that require you to purchase specialized parts and materials, such as barrels and springs from a supplier. You must also have or have access to expensive machine tools. It takes an experienced machinist or gunsmith to make these firearms. What I have come up with is a good happy medium.
The 22 Rim Fire I designed this gun around the 22-caliber long rifle cartridge for several reasons. They are easy to get, most sporting goods stores carry them, and they are inexpensive. They are also easy to hide and if stored in a cool, dry place, they may last as long as 50 years. You can literally carry hundreds of them in your pocket. Also, they have a low chamber pressure, which makes them safer for use in homemade firearms. The term “Rim Fire”, means just that. A sharp blow to the rim at the base of the cartridge will crush the rim, igniting the explosive primer compound, which then lights the gunpowder.
About the Gun The “Pepper Box”style incorporates the cylinder and barrel into one unit. This means you are not saddled with a precise alignment of the cylinder to a stationary barrel. I have also eliminated the complex trigger system that revolvers utilize. As you know, in a conventional revolver, pulling back the hammer revolves they cylinder and sets the trigger and hammer in the firing position. In this design, you manually rotate the cylinder to each station. To fire the pistol, you simply pull back the hammer with your thumb, aim, and release.
Simplicity There are only two moving parts on this gun, the cylinder and the hammer assembly. There are 25 essential parts, only six of which you must make yourself. The other 19 parts can be purchased at a hardware store. Appendix A lists the suppliers where you can obtain all the materials and tools necessary. In fact, you may want to visit your local machine shop where they may have all the stock you need in their scrap. If you are an experienced machinist you should be able to complete this design in about six hours. If you are a novice to working with metal, expect to spend significantly more time completing the project. There may be a small machine shop in your area that would manufacture some of the more difficult Page 3 of 23
pieces for you for a fee. If not, these plans are designed to guide a complete novice through the fabrication process. The instructions in this manual are geared more towards dimensioned drawings, illustrations, and photos rather than text. I believe this will make it easier for the builder to understand, whereas an experienced machinist only needs the drawings. I suggest using cold roll steel (1018). This is not the best steel to use in firearms, but it is easy to obtain and inexpensive. It is also easy to work with and has performed just fine in the prototype. If you have never worked with metal in your projects, I suggest getting more material than you think you will need. That way you will be covered if you make a mistake or lose a piece.
Ammunition The first thing I would purchase is the ammunition. 22 Long Rifle Ammo is still easy to obtain. But this can and probably will change at any time. Without ammunition, your time would be better spent making a good solid club. You will also need ammo to test your gun when you are finished. Testing will be covered at the end of the instructions.
In Loading Position
In Firing Position
Page 4 of 23
Getting Started
Figure 1 - Disassembled view of all components
Before you begin … … Study the text, drawings and photos carefully before starting work on the parts in this manual. If you build each part in the order presented, you may find the project to flow more smoothly. To highlight the lines, you will scribe on the parts to make them easier to see, mark over the area to be scribed with a felt tipped marker.
The Instructions The instructions in this manual are presented mostly as visual (i.e. dimensioned drawings, illustrations and photos) rather than explanations that can be misunderstood. This way, the beginner will understand the processes better and the seasoned machinist will only need the drawings. Most of the bolts, screws, and washers will have to be modified from what is supplied as stock. For example, the 10-32 cylinder axle bolt has to be shortened.
Page 5 of 23
Bills of Materials QUANTITY
SIZE
DESCRIPTION
1
10-32 X 2 ½”
Socket Head Cap Screw
4
4-40 x ½”
Socket Head Cap Screw
1
6-32 x 1”
Socket Head Cap Screw
2
6-32 x ½”
Socket Head Cap Screw
1
6-32 x 5/8”
Socket Head Cap Screw
2
#8
Flat Washer
2
#6
Flat Washer
2
6-32
Nuts
1
1/8”x ½”
Roll Pin
1
6-32
Pan Head Screw
1
¼”dia. x ¾”long x .032”
Spring
1
8-32 x .437”
Round Nose Spring Plunger*
1
1 ½”x 1”
Bar Stock
1
¼”x ½”x 10”
Flat Stock
1
¼”x ¼”x 2”
Key Stock
1
½”x .032”x 10”
Brass Flat Stock
*This item must be ordered from McMaster-Carr (www.mcmaster.com) catalog part number (3126A76 as of 2009) List of suppliers where you can acquire tools and materials: www.grizzlyindustrial.com www.mscdirect.com www.use-enco.com
Page 6 of 23
Minimum Tools Required Small drill press and drill press vice Dremel motor tool with carbide burrs Combination square with center finder 6”calipers Files Belt & disk sander Compass Taps: 4-40, 6-32, 8-32, 10-32 #2 center drill Drill sizes #43, #36, #29, #21, #1, #2, 15/64” V block (if your drill press vice doesn’t have a V cut in the jaw) Hacksaw 4”bench vice Center punch Hammer Hex key set 4: C-clamp Felt-tipped marker Magnifying Glass Scribe
Page 7 of 23
Using Calipers to Precisely Layout Hole Locations A pair of calipers can be used to precisely layout hole locations on your parts in the following way. Set and lock the calipers to the dimension you want to scribe the line to. For a rectangular part, you will need to scribe two lines in order to locate each hole. Scribe each offset down the length of the part. At the intersection of the two scribed lines, use the center punch to fix the location for the center drill. Note: Use a magnifying glass to help precisely align the center punch with the intersecting scribed lines. Caution: The center punch should have a sharp point in order to get the best results.
Page 8 of 23
The Cylinder Cut the 1”bar stock to approximately 1 7/16”(3/16 longer than the 1 1/4”finished length). Make his cut as straight as possible. The extra material makes it possible to belt sand the cylinder to the correct dimension so you get ends that are parallel (Since it is difficult to make a perfectly straight cut with a saw). Once you have finished cutting the cylinder, square up both ends to the proper length (1 ¼”). Find the center of the cylinder with the center gauge on your combination square. Scribe two lines, perpendicular to one another, all the way across the diameter. This will form an X with the center of the X being the center of the cylinder.
Choose one of the scribed lines as a reference line. From the edge of the cylinder along the reference line, measure ½”along the cylinder to an adjacent point on the edge. From this point, draw another ½”line in the same manner moving in a clockwise pattern around the circle.
Figure 2 - Scribing Pattern – Refer to Figure 6 for full detail on Cylinder
Page 9 of 23
After you have all the ½”marks on one side of the reference line, use the center-finder to scribe the line all the way across the cylinder. Now the radials forming the pattern are all marked. Carefully center-punch the center of the cylinder Set a compass to 0.325”and scribe a circle from the center. Where the radial lines and circle meet, these are the locations of the holes. Carefully center-punch the hole locations. You should have something that looks like the following:
Next, center drill all the center punched locations & drill them to size according to the cylinder drawing. (Note: Make sure your drill press spindle is square to the drill press or the holes will be angled. Use a V-block in your vice to hold the cylinder straight.)
Figure 3 - Center Drilling & Drilling Cylinder
If you have access to a mill or have a milling drilling attachment for your drill press, see Appendix A for the coordinates for drilling the hole pattern from the center of the cylinder.
Page 10 of 23
The Frame There are three parts to the frame: the base and the two cylinder yokes. These parts are made from ¼”by ½”flat stock. Saw the parts slightly longer than indicated so you will have some extra material to file and disc sand to finished size. Be careful to keep the ends parallel and square. Layout and scribe the hole and slot locations using calipers. To make the slot in the frame base, drill a series of holes along the inside of the scribed location of the slot, using a bit slightly under ¼”inch. This will remove the majority of the material.
After drilling all the holes, use the dremel motor tool with a carbide burr to grind out the webbing between the holes and rough-cut out the slot. File the slot to the finished size. Note: it is important this slot is as close to the correct dimensions as possible. Use the same layout and cutting method to make the two cylinder yolks as described above for the frame base.
Page 11 of 23
After you have finished making the cylinder and frame parts, you have to assemble them to see if they fit correctly. The easiest way to assemble this portion of the pistol is to start with the cylinder axle bolt, then just stack on the front cylinder yoke, then front spacer washer, cylinder, rear spacer washer, then screw on the rear cylinder yoke. Note: it may be necessary to reduce the outer diameter of the #6 washers so they do not interfere with the bullet’s path. This can be achieved by fastening them onto a bolt with a nut until tight then rotating the edge in your belt sander.
Attach this assembly to the frame base using the 4-40 screws. If you have trouble getting any of the four bolts to line up with the holes in the frame base or rear cylinder yoke, just re-drill the misaligned holes slightly oversized. This should give you enough clearance for the screw to be tightened.
NOTE: The screws in the picture are counter bored for aesthetic purposes, this is not necessary
Page 12 of 23
Firing Pin The firing pin is made from the 6-32 x 1”socket head cap screw and two of the 6-32 nuts and washers. The firing pin must have a taper on the end that strikes the cartridge. This pin should not come to a sharp point as that could puncture the shell casing upon discharging the weapon. To install the firing pin, first install the washers and nuts all the way to the cap on the screw.
Hammer Assembly The hammer is cut from the ¼”key stock. Use the same layout and cutting method to make the hammer as described above for the frame components. Check to see how it fits into the slot of the frame base. It should slide into the slot easily, without binding. If it doesn’t, file the slot until it slides easily. The hammer assembly is held into the frame base with a ½”long 1/8”diameter roll pin. Screw the firing pin into the hammer and install the safety screw.
Page 13 of 23
Handle The handle is formed from a strip of ½”x .032”brass. To make it easier to form this handle, use the pattern shown here as a template. Note: Be careful when drilling brass as the drill tends to bind in the material. After you have formed the handle, place it in position on the frame base and mark the locations of the holes through the 6-32 handle mounting holes on the frame base. The following image is to scale, you can use it to help shape your brass handle, or adjust the shape to your liking.
Figure 4 - Brass Handle Template
Page 14 of 23
Setting the Timing on the Cylinder With the cylinder installed in the frame and the 8-32 x .437 spring plunger installed, use a felt-tipped marker to mark a band around the cylinder, in line with the spring plunger. Tighten the spring plunger until it depresses the ball slightly. Note: The spring plunger will tend to back out, you may want to consider using a jamb-nut to prevent this from happening, but it is not critical to the fabrication of the gun. Rotate the cylinder 360 degrees to scribe a line all the way around the cylinder. Rotate one of the chambers on the cylinder to top dead center position. Tighten the axle bolt. This will keep the cylinder from rotating while you are drilling the detents. Align the center drill top dead center on the cylinder over the scribed line. Clamp the vice to the drill press table.
NOTE: This is a good time to check that there are no obstructions to the chamber. With your #2 center drill, make a shallow indentation (just deep enough for the spring plunger to engage). Repeat this procedure for all six chambers loosening the axle bolt before moving to the next chamber each time. NOTE: After you have drilled three chambers, the ball will detent in the first hole you drill. This will automatically locate the remaining three detent holes.
Page 15 of 23
Spring Anchor Screw The spring anchor screw is made out of the 6-32 pan head screw. Shorten the screw to about 5/16”in length. Drill a 3/64”hole in the screw about 1/8”from the face of the screw head. Hook the hammer spring into the small hole at the bottom of the hammer assembly, then through the hole on the spring anchor screw. As you pull on the anchor screw, the hammer moves forward, toward the cylinder. With some tension on the spring, mark on the handle where you need the hole for the spring anchor screw. Drill this hole slightly over-sized so the anchor screw will slide in easily. Insert anchor screw through the hole and fasten the spring to the anchor screw and hammer.
Page 16 of 23
Testing Now that you have completed your gun, you will need to adjust the firing pin and test fire the pistol. The lower screw on the hammer assembly serves as the safety. When this screw is all the way forward, the gun should not fire. It is your responsibility to ensure the safety screw you are using is long enough to force a gap between the firing pin and the cartridge.
Adjusting the Firing Pin With the firing pin assembly installed in the frame base, remember you want the firing pin to hit the rim of the cartridge. To make the firing pin hit lower on the rim of the cartridge, back the firing pin out of the hammer. To make it hit higher on the rim, screw it in a little. Once you have the proper adjustment, tighten the nuts against the hammer to lock the firing pin into that setting. To test the pistol, carefully remove the lead bullets from six cartridge cases. To remove the lead bullet from a case, grasp the bullet with a pair of pliers and with your thumb, push on the brass case until the bullet dislodges. Dump the powder, leaving just the primer compound in the case. To load and unload these cases into the pistol, rotate the cylinder until the chamber is fully exposed to the loading port.
Point the gun in a safe direction, pull back on the hammer with your thumb, and then quickly release. This may take some practice. If the gun fails to fire, check the firing pin mark on the case rim. It may need further adjustment, or the spring tension is not quite right. If the gun fires, you will hear a small pop, like the sound of a cap gun. Rotate and fire all remaining chambers in the same way.
Accuracy The compact nature of this design does not lend itself to accuracy. Even with rifling the barrel is very short and would still be inaccurate. When range testing the prototype, I discovered the gun to be fairly accurate at about 10 feet holding an 8 inch diameter grouping at that range. Beyond that the accuracy falls off rapidly.
Page 17 of 23
Figure 5 – Handling Technique
Appendix A Milling Coordinates Milling Coordinates Referenced to Center of Cylinder
Hole
X
Y
Axle
0.000
0.000
1
0.325
0.000
2
-0.325
0.000
3
0.162
0.281
4
-0.162
0.281
5
0.162
-0.281
6
-0.162
-0.281
Page 18 of 23
Figure 6 - Cylinder Dimensions
Page 19 of 23
Figure 7 - Frame Base Dimensions
Page 20 of 23
Figure 8 - Front Yolk Dimensions
Page 21 of 23
Figure 9 - Rear Yolk Dimensions
Figure 10 - Hammer Dimensions
Page 22 of 23
Supplemental
Placing the jamnut on the spring plunger will prevent it from losing its adjustment. An issue that some builders have had trouble with, is the cylinder spacer washers. Be sure to make the rear spacer washer thicker than the case rim of the cartridge. (The thickness should be .047 – .050). If the rear cylinder spacer washer is too thin, it will not allow the cartridge to clear the rear yolk. Make the front cylinder spacer washer whatever thickness is required for a good fit. While carrying your pistol, you should always carry it with the firing pin over an empty chamber in order to prevent it from firing accidentally. Also, Ace Hardware is also a good place to purchase the hardware, i.e. the spring, socket head cap screws, and the .500” x .032” brass strap.
Page 23 of 23
