Paintball Minigun HK-1

I have been wanting to build a Paintball Minigun for a while and I decided now that I have the resources to make it happen, I should get this thing finished. Also please ask me if you have any questions, I would be more than happy to help.

Thank you, and happy building!

To build this Minigun a bunch of the parts that I needed were not available so I had to design them myself and 3D print them. This project took me about 2 months to build which I did not work on it every night. Most of the time was spent just figuring out how to design what I wanted.

The video above was the first time taking this bad boy out for a spin. This is not the top firing rate. I need to take some time and tune it in. In the video I show the barrels spinning by themselves, then the barrels spinning while dry firing, then firing the paintballs. Its hard to see the paint because I used green paint...Enjoy!

Step 1: Main Chamber

The first thing I decided to do was to design a back ring that would attach the barrels to my bearing. I designed the "Rear Barrel Ring2" below and 3D printed it. I then tapped the 4 inner and 4 outer holes with a #4 tap. I then screwed the Rear Barrel Ring2 to a 4" lazy susan bearing using the 4 outer screws. Once that was done I marked, drilled and tapped 4 holes in a 25 tooth nylon sprocket. I got a 3-4" PVC Reducer coupling and marked the bearing with the inside diameter of the coupling and on the barrel ring of the bearing I cut the metal corners off so the would not rub as the bearing spins. On the Sprocket side I folded the corners up so the whole thing slides into the 4" side of the coupling. Then I secured the bearing to the side of the Coupling with 4 screws. Finally I cut 2 slot in one side of the coupling so the chain could travel through. I also had to drill the center of the main sprocket out to about an inch so the barrel could fit through later.

Step 2: Motor Housing

I bought the cheapest cordless drill I could find at Menards so that I could use the motor and the battery to power the barrels. I opened up the drill and you need keep the battery hook up and the motor with the torque setting chuck. You need this chuck because you can set it to 8 or 9 and if you ever get something stuck in the spinning barrels it will activate the chuck and not break your barrels.

To mount the motor I designed a ring that will fit on the motor and screw to the motor with 3 screws already holding the motor together. Then I purchased a 2" compression fitting, slid the motor inside and secured it with 3 screws through the 3D printed Motor Mount Ring. I then cut a slit half way around the PVC tube so the chain could go through. I also drilled a small hole toward the end so the wires could go through.

I took the cap to the compression fitting and cut the top off to make it as short as I could. Then I 3D printed a plug to fit inside the cap to close it off. I glued this cap into place. Now the cap is still removable so that the chain can be accessed later.

I also made a cap to be glued on the back of the compression fitting and this cap has holes in it so the motor can breath and not overheat.

Step 3: Mounting Motor to Main Chamber

To mount the motor housing to the main chamber housing I had to 3D print a dual ring to hold these together. Once printed I hooked up a nylon chain between the motor and the main sprocket. I made sure this was aligned and slid the mounting bracket over the 2 housings and secured them both with the 3 screws in each of the housings through the mounting ring. Then I developed a chain guard so nothing gets caught in the chain. I used 2 screws in each of these to hold them on.

Step 4: Regulator and Handle Mounts

I added a 3" tube of PVC to the main chamber and also on the side to house the regulator. To mount the regulator housing to the main chamber I had to create another dual ring mount that was slightly different than the first one for the motor and I used 2 of these.

Next was to mount the 2 points to where the handle will attach later. I used 2 pieces of 1-1/2" couplings and designed a base to connect them to the main chamber. I first screwed the couplings to the 3D printed base then screwed the base to the main chamber. Then I put a Plug cap inside each of the couplings and screwed them into place. These allow the square parts to be easily mounted to later with the handle.

Step 5: Internals

Now for the goodies...

I used a Smart Parts Ion Paintball Gun for this project. I used the main chamber of the gun, electronics, regulator, and ASA.

I purchased a remote quick connect and replaced this straight connector with the 90 degree elbow that was on the regulator. Then I bought a 1/8" micro line fitting to replace the fitting that was in the ASA. I put all of this together in the 4th image above.

To mount the regulator I used the mounting holes from the ASA and I had to develop and 3D print a mount so it would mount to the rounded interior of the regulator housing. I mounted the regulator so the adjustment nut is sticking out past the housing.This is so we can adjust it later.

Step 6: Internals 2

On the guns circuit board I had to locate the power, program, and trigger buttons and solder a wire on both sides of these switches. Make sure you label these so they will be easy to find later. I also had to get some 1/8" and 5/32" tubing so that I could extend the hoses to reach the new locations for the regulator and such. To attach the gun to the inside of the main chamber I had to design more rings to tighten to the gun using bolts to squeeze the gun then the rings have 3 holes to mount to the inside of the main chamber housing. Once the rings are installed, the electronics need to be crammed in between them and zip-tied. Now the feed neck needs to come off so the gun can be slid into the main chamber.

Be sure to drill a hole in the side of the regulator housing and the main chamber for the air lines to fit through to the regulator .

Step 7: Handle

To make the handle I first started with taking apart an old Sidewinder flight controller. After digging down deep into the controller I only needed a few components. I only used the grips, the buttons, the circuit board, and the post that the grip holds onto. Then I chose which buttons on the controller that I wanted to do used. I needed 4 buttons: one for power, programming, motor spin, and firing. I found which buttons were which by using a multimeter and checking continuity of the wiring until I found the buttons that I wanted (2nd and 3rd photo).

Then I soldered wires to the circuit board on the paintball gun. I soldered a wire on each side of each of the switches for power, programming, and firing.

I built the handle out of 1/2 inch square metal tubing and some 1/2 inch rod. I welded all of these pieces using a mig welder. Please see photo notes as to where each of the following parts are located.

The following lengths were cut from this 1/2 in square tubing:

2 pcs. 5" long

1 pc. 3.25" long

2 pcs. 11.5" long

4 pcs. 2" long with 1/4" hole drilled in them

1 pc. 4.25" long

1 pc. 8.25" long

1 pc. 1.75" long with 1/2" hole drilled in it

The following was cut from 1/2 in rod:

1 pc. 7" long

2 pcs. 2.25" long

1 pc. 5.25" long for under the handle later

Once the handle was made I uses a 3" to 2" fitting and put it on the back of the main chamber. Then I 3D printed a disk that has a recessed hole in the center for the 1/2" tube to fit (see "Shaft Support file"). I glued this disk inside the fitting. The front of the handle is secured but drilling a 1/4" hole through all 4 front tubes and the square caps on the front of the handle supports. Then use some 1/4" quick release pins so you can easily disassemble later. The back is supported by drilling a 1/2" hole through the 1.75" short tube under the handle. Then slide the 5.25" round tube through that and into the hole in the back of the main chamber. Fasten the round tube to the square ube by drilling a small hole and using a small bolt and nut to keep in place.

Step 8: Battery Holder

The drill motor needs its own battery that is seperate from the guns 9v battery. I used the battery that came with the drill which was 18v. I also used the connector at the bottom of the drill as means to attach the battery to the gun. I took the drill body with no internals and cut off the bottom of the grip. Then I drilled 4 holes, one in each corner to mount it to the underneath of the gun. I drilled a hole in the regulator tube so the wiring could go through and be hidden.

Step 9: Wiring

The wiring is pretty much straight forward. I drilled a hole out of the back of the 3" X 2" reducer at the back of the main chamber. This is where all the wiring will run out from the gun and to the trigger grip.

Run the power wires from the gun circuit board and wire them to the power wires coming from the grip, and do the same for the program wires, and the firing wires. For the last set of wires hook the ground wires from the battery connector directly to one of the wires coming from the drill motor, take the other wire from the circuit board and run it to one of the wires on the grip that you want to use and take the other wire from the grip and run it to the other wire on the drill motor. You should be able to put your drill battery in now and hit the rotate button on your grip and it will spin. PLEASE be aware that there are no safety switches here and take out the battery when you don't intend on shooting it.

Leave enough slack in the wiring that you can take the handle off the top and place it to the side without stressing the wires. Also I used wire loom and wrapped the wires going from the back of the housing to the grip, from the motor housing to the main chamber, and from the regulator housing to the main chamber.

Step 10: Barrels

For the barrels I used 6 pieces of 1/2" ID and 5/8" OD PVC pipe that are 22" long. These are for the main 6 barrels. Then I used 5/8" ID blue PEX piping, which I used 6 of these at 10" long. These slip over the back of the barrels. Last I use a 1.25" ID PVC pipe that is 22" long that will run on the inside of the barrels for support and to hide the paintball gun barrel.

I 3D printed 4 more disks just like the one I mounted to the bearing but these 4 are through holes and so the barrels will slide through them. I put the first ring about 10.25" from the ends of the barrels. Then I slid the blue pex tubes over the barrels until they pushed up against the ring I just put on. This will allow about 0.25" to stick out of the pex at the back of the barrels. This will allow the tubes to sit down inside the disk that is attached to the bearing later. I took the next 3 rings and put the 1st one about 1/2" from the front of the barrels, the next at 1.75" from the first and the last one at 1.75" from the last one. Then I slid the 1.25" tube through the center of all of the disks and made it flush with the front of the front disk. This should allow for 0.25" to seat into the ring on the bearing.

I used a lot of a glue called Plastic Repair that I picked up from Farm and Fleet. This stuff is great and really sticks the PVC to the 3D printed ABS material. I tried 5 minute epoxy but it just breaks off and your barrels will fall off. I used this Plastic Repair around the barrels and rings as I could get access to. Once that dried then I took the barrel assembly and seated it into the ring on the bearing and glued it as much as possible. Be careful not to glue the bearing in place.

Step 11: Final

Once everything dries it is time to paint it. I used a plastic primer and a textured flat black that I picked up at Lowe's. Make sure you plug up all of the holes so the motor and paintball gun do not get painted.

Overall I am very happy with this build. The barrels wobble a little when they get spinning but that is due to the play in the bearing and I could get a tighter bearing if I wanted to fix it. The gun has not been adjusted, only to switch into full auto mode. I have not tried to get a faster rate of fire yet but I will be doing that soon to see how fast I can get it to shoot. Also later on I plan on putting and elbow where the hopper is now and run a tube to a backpack and have the paint force fed in since my tank will be on my back anyways.

I hope you like my Paintball Minigun HK-1. If you do PLEASE vote for me above in the right hand corner to show your support and I will keep the projects coming. Thank you for looking and please let me know if you have any questions.

Happy shooting....