Introduction: Build the Matrix "Auto-Shotgun", a Cool Nerf Version.

About: Me? I just love building this, fixing that, and on the rare occasion creating stuff. I really enjoy repurposing the things I find and collect while working. Pre-enrolled into the Ohio State Engineering Sc…

Second Note-  I know I look pretty shaggy in the video. I had just finish building, hadn't shaved in a few days and was too exited to show off my gun to go make myself look better.  Also, I apologize for fliping the bird.  I lost my index finger in a table saw accident at work so I have to point with my middle finger. 
  Hello Nerf enthusiasts and Cos-play actors, Makers, Movie lovers, Freaks, Geeks, and Mystique's.  Welcome to instruction in the building of a functional Nerf version of the auto-shotguns used by Mouse in the movie The Matrix.  Ever since I was introduced to the art of Nerf modding, I knew this was something I had to do as these are my favorite movie guns.  Although I could have simply made replicas of these guns, the fun part for me was figuring out how make a working version.   

  These guns were custom built for this movie by John Bowring, a builder of weapons used in movies.  If you've ever seen a movie gun that made you say "wow, that's cool..." , chances are that this guy built it.  These are cam driven, 25 round, rotating drum, automatic shotguns.  What this means (I'm pretty sure anyway) is that the trigger activates a motor, located at the top of the gun, which turns the drum.  Behind the drum is a spring loaded firing-pin that strikes each shotgun shell as the drum turns.  Firing rate is determined by the speed of the motors that turn the drums. The genius of these guns, besides how awesome they look, is the simplicity of the whole system.  Our versions of these guns are, by comparison, much more complicated; but as you can see, very do-able and worth the time put in to building them. 

  It was both a blessing and curse that these guns were only onscreen for a few seconds. You only get a visual of the front half of the gun, so what's the back half supposed to look like....?  Answer: Whatever I want it to look like, or more accurately, whatever I need it to look like. The most difficult part of this project was incorporating the automatic mechanism of the Nerf Vulcan into the body of the Nerf Firefly, kind of like Dr. Frankenstein's monster.    

  Here's a quick overview of what you will be doing to complete this project.  We will be removing the automatic firing mechanism from the Nerf Vulcan.  Redesigning the body of the Nerf Firefly to accommodate  this mechanism.  Building a trigger to activate it.  Building a drum to house the ammo chain from the Vulcan.  Finally, relocate and build a housing for the light that was in the Firefly.  Simple, right?

  Take your time with each step and focus on the details, making everything fit together smoothly, before moving on to the next step.  I will say that having a 3D printer would have made building this gun much easier and more accurate, but I don't have one. 

  This project took me a while and, although the focus was not on making an exact copy, is very involved.  It does require some electrical and mechanical know how.  Being an unconventional build, some of the way things fit together will be up to your judgement.  I will be guiding you through the process of constructing the pieces to the best of my ability and hopefully in the end, you will have a truly unique Nerf weapon.

Step 1: Tools and Supplies

Firefly gun, and Vulcan gun


- drill, large variety of bits, one 3/4" spade bit and one 5/8" spade bit, and one 1" spade bit
- sodering iron, solder
- hobby knife
- jig saw
- dremel
- wire strippers
- screw driver
- compass
- pencil
- hot glue gun, glue


-4"  PVC
- bondo
- spraypaint
- super glue
- wire nuts
- electrical tape
- masking tape
- fine sand paper
- 10" foundation tube
- 1/4 plywood
- screws

Step 2: Inner Workings

This is the internal workings of the Vulcan. This picture is meant as a reference to the various parts I'll be talking about in the next several steps.  I have numbered the important parts for easy reference.

#1  Electronic switch
#2  Electronic switch
#3  On/Off switch
#4  Battery terminal
#5  Battery terminal

Step 3: Dr. Frankenstein's Monster

As the title says, we're going to do some unconventional surgery to combine two Nerf guns to create a Monster Nerf Gun.

  First open the Vulcan, there are a million screws, save them in a safe place.    Once done, removing the automatic mechanism is pretty straight forward.  Be sure to keep all the attached wiring, switches, and battery terminals intact.  You will need to disconnect the on/off switch from the body but again, make sure to keep the wiring intact. 

  One thing I found out about the wiring is that it's thin and the solder points are weak, so it might be a good idea to label the wires and connecting points in case you need to re-solder them.

  Next, open up the Firefly and remove, but save, everything. 

  Now comes the scary part, in order for us to incorporate the parts from the Vulcan, we have to cut away a significant part of the Firefly body.  It was hard for me to do, I thought, "I can't believe I"m destroying a perfectly good Nerf gun".  It has to be done though, so take a deep breath, and exhale.  Everything will be OK.

  If you need a guide line, take the Vulcan mechanics and use it to draw a cutting guide out of a piece of cardboard.  This works well for the general outline, and to remove the bulk of what will be cut out of the Firefly body.  After making this general cut and removing the bulk , I would repeatedly try inserting the PVC into place with both sides of the Firefly body put together.  This will help you see in more detail where you need to cut, and grind. Your goal is for the PVC to sit nice and level, with as little gap along each edge as possible.

Step 4: New Housing for the Mechanics

I opted for a fairly simple housing for the mechanics.  A length of 4" PVC works nicely when modified a bit.  I considered making a housing out of acrylic, but this works well and I think it really looks good with the Firefly.
   A quick cardboard cut out can be made for measurement purposes if you need it.  
Measure for a square cut-out on the underside to allow the motor to stick through, and a square cut-out on the top to allow the "on/off switch mount" to stick through.  The cut out on the top does not need to be as large as the one I made, but I wanted to be able to see most of the mechanics after it was all put together.
  After you make this opening, cut out a piece of PVC slightly larger than the opening, from another piece of PVC.  This will be the cover for the opening in the top.  Drill a small hole in each of the four corners and screw the cover into place over the opening.
  This is all that really needs to be done to accommodate the Vulcan mechanism, although you will need a slit cut down the top side connecting with the on/off switch mount cut out.  This slit will allow you to slide the mechanism into the PVC.  See the pictures for better understanding of this.
  A quick note about the " on/off switch mount".  If you're not planning to put your Vulcan back together, cutting this switch mount off will make the whole thing fit into the PVC much better. It's not needed for our gun to fire, especially since the on/off switch won't be mounted there anymore.

Step 5: Aligning the Mechanics

  By this point you hopefully have the Firefly cut down right and the PVC sitting in it well. 

  One of the reasons I chose the Firefly was that it had a drum guide right on the front of it already.  When I laid down the PVC with the Vulcan mechanics in it into the Firefly, the drum guide was just a little bit high to fit.  I wasn't going to let a little height difference put me off, so I cut a little out of the drum guide.

  I'd like to be able to tell you exactly what length to make it, but it's dependent on your cuts to the Firefly body, and how high or low your PVC tube sits in it.  To measure the amount you need to cut out, set the PVC tube with the mechanics into place and add the chain gear.  Slide the PVC forward until the chain gear touches the drum guide.  Measure the relative offset, and that's the amount you want to cut out of the drum guide.

 To put it back together I used a splint, made of a small square of PVC, a couple screws, and some Liquid Nails.  Its getting old saying this but,  check out the pictures.    

Step 6: Wiring Your Gun

  Before you mount these components, I found it very convenient to separate them first.  I mean that literally, mark the wires with different color tape or numbers, then cut the wires in the middle between each component.  This will allow you to mount each at your leisure, and it will let you move each part of the gun around without having them attached to each other.  Trust me, you will need this flexibility.   We'll reconnect the wires when we close the gun up for the last time.

  The easiest way to do this will be for me to run you through the circuit, from the negative battery terminal to the positive battery terminal, pointing out component locations as we go.

  OK, well the battery terminals will both come right out the bottom through a hole of your making or, as I have done, through one of two existing holes that originally held a small strap anchor.  Having the Firefly in front of you, you know what holes I am referring to.

  From there, the negative terminal wire runs directly to the motor in your PVC tube.  From the motor, the positive wire will run to the first electronic trigger switch.  The first switch is mounted on the left half of the Firefly body.  In the next step I'll explain the electronic trigger switches and their placement in detail.

  From the first switch, the wire runs to the on/off switch.  I mounted the on/off switch above and behind the trigger on the left half of the body.  This makes turning the gun on and off easy with the thumb of my right hand.  If you're left handed, I would mount it on the right half of the body.  As you can see in the pictures, I cut a small square hole with my rotary tool, poked the switch through, and hot glued it into place.

Step 7: Remaking the Trigger

  This trigger assembly is completely custom.  It has to activate both the trigger switch and the safety switch of the Vulcan at the same time for the Vulcan mechanics to activate. 

  How I achieved this was to mount both switches side by side,  one on the left side of the Firefly body, one on the right.  They are situated in a niche already existing in the Firefly body, about three inches behind the trigger.  The switches are positioned facing towards the trigger, with the tiny circuit board facing up.  The niche fits the electronic switches almost perfectly, but you will need to make a cut out on the top for the tiny circuit board attached to the switch.  Be sure to put the two halves of the Firefly back together with the switches in position, do this to make sure the switches sit exactly side by side.  Make any adjustments necessary and then hot glue them into place.

  In order for the trigger to strike both switches at the same time, a "T" must be made on the end of the trigger.  It can be made out of any scrap piece of plastic you have.  Make sure that there is enough length on the trigger so that it strikes the switches when pulled back on.  To measure this, put the trigger into place on one side of the Firefly, in the fully engaged position (pulled all the way back).   From there, measure back to the electronic switch and cut.  Then attach your "T" piece with superglue.

Step 8: Map Out and Cut the Drum

  OK, Finally.  In this set I can give some exact numbers for you to use.  My drum has 24 shell in it, one less round than what comes on the Vulcan belt, so cut one off.  The reason for this is to make the math and measurements easier.  Now, a little math.  360 degrees divided by 24 shell equals one shell every 15 degrees.

  Our drums outer circumference will be 10 inches so cut 2, 10 inch circles from your 1/4 inch plywood.  Mark out 15 degree lines using your protractor.  I found it easiest to draw a straight line on the wood first, then set your protractor point on the line somewhere and draw the circle.  This leaves you with a line exactly through the middle of your circle, which will make measuring your 15 dregree lines easier and more accurate.

  Now, Take the dart chain and hold two shells over the circle near the outer edge.  Move them toward the center of the circle along two of the radius lines.  When the lines appear to go through the center of each shell, this is where you want to drill the shell holes.  With your compass, draw a circle at that point.    Copy this on the other piece of wood.

  At the point where this circle intersects the 15 degree radius lines you will want to drill a hole.  Use a 3/4" spade bit to drill the holes one one f the pieces of wood, this will be the front of your drum.  Use a 5/8" spade bit to drill the holes on the other piece of wood, this will be the rear of your drum.

 Now, using your compass, draw a circle 1/4" in from the shell holes, and one 1/4" out from the shell holes.  With your jigsaw, neatly cut along these lines.  When you are finished, you should have two large nearly identical rings, with 24 holes in each. 

Step 9: Finishing the Drum

From the 10" cardboard foundation forming tube that you have, cut a 3" section.  This will be the outer skin of the drum.

  With the two wooden circles cut and all of the smaller holes drilled, putting the drum together is a simple matter.  There will only be 24 round holes so one of the rounds on the Vulcan chain will have to be cut off, at that point the chain shells can be inserted into the 24 holes.

  The front holes should be a tight fit and the chain shells should be mounted flush with the front of the wood circle.  The rear wood circle will be slightly loose, but that's OK. 

 Put down a bead of glue on the edge of each wooden circle and then wrap the 3" cardboard ring around the drum.  Cut any excess off and then tape the circle into place.  When it's dry, you'll have a 24 round drum that should rotate perfectly with the gear of the Vulcan mechanics. 

 Apply a coat of bondo to the entire outer surface.  It should only be a few minutes until the bondo is dry.  When dry, sand it all down smooth, as shown in the pictures.  I had to repeat this a few times to achieve a totally smooth surface.  It also helps to spray on a coat of primer between coats of bondo.  This makes it easier to see low spots where more bondo is needed.  

Step 10: The Front Face

  This part of the gun is very important.  It acts as a guide for the drum to turn on, and the front face where the barrel is attached.  You want this front face to overlap the drum slightly, but not the bullet holes.  Mine came out to 8"  but measure the inner diameter of your drum just to be safe.
  When you are pretty sure of your measurement, draw a circle on a piece of 1/4" plywood.  Now, on the top of that circle draw a very large triangle.  Cut this out and, with the drum on your gun, hold it up to the front.  Does it slightly overlap your drum, but not the bullet holes?  Is the triangle large enough to meet the front of the Firefly shell?  When you can say yes to these questions, draw a second circle about an inch smaller in diameter on this piece and cut it out.  You should end up with an 8" ring with a large triangle on top.   
  Now you have the basic shape of your front face, and it just needs to be fine tuned.

  Cut another 3" piece from your foundation tube. Now cut across it at one point so that you can adjust its circumference. Line this up along the inner edge of the face and mark it where it reaches about 3/4 the way around. Glue this piece to one side of the face just inside of the inner edge, with the gap centered at the top.

Step 11: Mounting Front Face

  I found mounting the front face to be an in exact process and someone else may now of a better process, don't be afraid to expierement.  First hold the face up to the front of the gun and mark two spots where a screw could pass through the face and into the plastic of the gun.  Drill two pilot holes through these two spots on the wood. 
  Now screw two screws through these holes so that they stick out the other side about 1/4".  Hold the face up to the front of the gun again, and line it up to where it needs to meet the gun.  Press the screws into the plastic slightly so that it leaves two small indents.  Drill two pilot holes in these indents.
  Your front face should screw right onto your gun now, so do that.  Check it out and make sure its straight and that it lines up well with the drum.  Make any alterations nessesary.
  When it's all lined up, mix some bondo, and fill in the gap between the gun and the face.  when thats dry, sand it down to a smooth transition from gun to face.

Step 12: The Barrel Mount

We need to make a mount that will hold the barrel in place on the front face of your gun.  For this we'll use some more bondo.  Take the Vulcan barrel and wrap a piece of wax paper around it.  Use a piece of scotch tape to hold it in place.   Now tape a peice of wax paper to your desk or work bench or whatever surface you are working on, though it must be a flat, level, smooth surface.  Mix a rather large amount of bondo on your wax paper.  Use a putty knife to spread bondo all the way around one end of the barrel, and about 3-4 inches up from the end.  Now pool the excess bondo still on the wax paper, into a 4-5 inch circle.  Mash the end of the barrel with the bondo on it into the center of the circle on your workspace.  It should stand up on it's own, just make sure it's standing up striaght. 

  When that is dry, you should have a rough form of your barrel mount.  Using your rotary tool with a sanding attachment, smooth down the rough surface and your barrel mount is ready to be fitted to the front face of your gun.

  This Is where a 3D printer would be nice so if you have one, do it up!

Step 13: Mounting the Barrel to the Face

  With the face mounted to the gun, measure the distance from the inner diameter of the face to the center of one of the bullet holes.  Remove the face and put it face down on your work space.  use this measurement to mark the spot where you will drill a hole for bullets to pass through.  Use your drum to find this location on the face.  Center it as much as is possible, but don't worry if it's slightly off.  Using the 1" spade bit drill your hole.

Now position the barrel mount on the front of the face, drill a few pilot holes, and screw it to the face.

  This pretty much wraps up building the gun.

Step 14: The Flash Light

  As I said in the introduction of this instructable, there is a motor placed on top of the drum which turns it.  Since we are using the Vulcan mechanics to turn the drum and generate air we don't really need that motor, but for the sake of appearance I needed to put something up there. 

The Firefly has a light in it that illuminates the glow in the dark darts, so I decided to use that light and its existing wiring to make a tactical flashlight where the motor would be.  For this, I used a Morton salt container which is the right size and shape for what I wanted.  The lid also has a nice little hole in it perfect for the LED that indicates when the light is on.  (If you choose a different container to use, you will need to make you're own alterations as you see fit.)  You're going to need to cut the wires that go to the light and LED in order to put this light together, so tape and number each wire so you know how to reconnect them.

Putting this light together is pretty simple. First I cut the bottom of the container out, leaving a small rim around the edge.  The I used my rotary tool to grind the down the corners of the reflecting mirror of the Firefly light, so that it will fit inside the container.   Use some bondo to keep the light in place and seal the end of the container around the light. 

On the lid side, put the LED through the hole and wrap some tape around it.  The tape will keep the LED clean of the bondo you will use to fill the small indentation in the lid.  When it's dry, sand it down smooth, but keep the tape on the LED. 

Put some tape over the front light and reflector, and put the container back together.  Paint the whole thing.

When its dry, open it up, position it on the top of the gun where the tactical rail is.  drill a small pilot hole through the inside and into the gun.  Screw it to the gun. 

Now reconnect all of the wires.

Step 15: Paint

Once all the parts are built, it's time to paint As you can see, mine is painted to resemble Mouse's guns in the movie. 

 Before you do any painting, its a good idea to use some very fine sand paper to rough up the plastic a little.  (actually, a painters fine sanding block will work the best) This will help the paint stick better.  After that, it's also a good idea to apply at least one coat of primer.

  Whatever color scheme you choose, this gun will definitely draw attention from any who see it.

Step 16: The Battery Belt

  The Vulcan uses 6 D cell batteries to run it's motor, which obviously cannot fit into my gun.  I decided because of this to relocate them to a case that can be worn on my belt.  The power is then sent to the gun through a wire which connects to the gun using RCA jacks.

  I used a canvas pouch to hold the batteries, it's very similar to a fanny pack.  Anything like this will work, or you could sew your own if you're good at that type of thing.

  One more thing I should tell you... I used 8 D cell batteries, which increases the voltage from 9 to 12 volts.  This speeds up the motor and increases the rate of fire.  It was my intention to do this anyway, but the battery holders I bought from Radio Shack were set up to hold four batteries a piece anyway.  It's not something you have to do but it's cool. 

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