Intro: Radiation Kid Gun Build
Basic re-build of a toy gun into a prop suitable for any holidays, films or conventions. Includes instructions for modifying the body, resurfacing the exterior and basic painting techniques. Simple steps also cover the addition of an LED array and laser diode for interactive flava.
This fun project takes only a few hours and can be accomplished with a minimum investment of supplies and tools.
Step 1: Find a Gun
Find a gun to use as a base for your project. I've heard a lot of loose talk about steam punk guns of late, but for this project I was looking for something a little more like Hellboy's "The Samaritan." That is heavy, high caliber and steel. This gun body was a perfect fit and only $2 at my local urban appropriation center. It started life as a playstation light gun and was full of more electronics then your run of the mill toy pistol.
After removing all the screws holding the case together I examined the contents. Of the original hardware I'm going I kept the trigger assembly and the A/B buttons. Everything else got cut out. Be careful to leave longer wires connected to parts you might use, this will save extra soldering later on.
I like to photograph the insides of things as a i take them apart, so i know where everything goes during the rebuild. There's nothing worse than being done and not remembering where that last bolt goes.
Step 2: Filler
Plastic filler is going to be your best friend here. Chose a plastic sandable filler with a quick dry time. I used a 2 part marine putty to fill in the names and logos from the sides of this gun. The putty comes like a jelly role in a plastic, air tight tube. It's white in the center with the blue activator on the outside. Kneading the blue/white parts together starts the reaction and you've only got 2-3 min. before the compound starts to set up. Sand as much of the gun surface as you can to provide a "tooth" for the putty to stick to. Mix/apply quickly and in small batches to keep the putty pliable enough to smooth on without clumping. Feel free to pack it into small cracks and move on, extra material will be removed later and speed is a virtue at this point.
Check the manufacturers directions for drying times, but 15-30 min should be enough for 2 part compounds like this one i used. For flat places use a flat chisel or craft knife to remove the excess filler. Lay the blade flat against the surface and try not to gouge into the compound, just shave off the top most layer. Patience at this stage will give you a relatively flat surface that you can bring down further with sanding. 100 is a good medium grit that makes fast work without leaving to many deep scratches.
For curved sections like the bottom of the gun handle, rough out the shape with a chisel then slowly finish with the sandpaper. Check often to make sure your shape is correct and your not unintentionally sanding unwanted sections as well. If you accidentally over work a portion, just apply another dollop of filler and start over. The project is still very workable at this stage, anything goes.
Step 3: Electrical Stuffs
Internal components ad an extra bit of nerdcore to your already geeky prop gun. Inspired by projects with chasing LEDs and sound chips i originally wanted to cram everything i could into this build, but the relatively small size of this gun body limits the amount of stuff you can cram inside. Settling on a UV LED array and laser, i collected the necessary parts from dealextreme, a hong kong based supply for all things cheap and battery powered.
For the light i removed the 9 led array board from a flashlight and de-soldered the white diodes replacing them with UV leds from eBay. These diodes are cheap, offer no filtering and deliver lots of harmful UV in one direction. Don't look into them or point at your friends eyes. Do check out suspicious stains on their clothes. I was able to salvage the on/off witch from this flashlight, i think i will use it someplace during the build. Start thinking of places to mount it.
The place I want to mount the laser is cramped by the A/B buttons. I'm going to have to remove most of the metal shell from the laser pointer to make it fit; doing this will allow me access to the on/off switch as well. Relocating this switch to the trigger assembly will make this gun much more realistic. Every time the trigger is pulled there will be an audible click and visible red dot on the target. It lends this project some sense of respectability.
After locating the laser switch, bypass it with a wire just behind the diodes single resister. Now you can use any switch to turn the laser on, not just the one it came with. At this point I'd like to mention this laser ran off three 1.5v button cells. I'm going to use three 1.5v AAA batteries to power it from now on. Button cells are expensive and a pain to find, your better off with cheap, easy to locate AAAs for longer life and fewer battery changes. Care should be taken to supply correct voltage to your diode, my LED array and laser just happen to both run on 4.5v. Lucky me.
Step 4: Digging a Hole
Lay out the places you want all your electrical pieces to go. Close the case to make sure everything fits. If you're good it's time to dig a hole big enough for the flashlight button to fit into. After marking the size of the hole on the bottom of my gun grip with a felt pen I roughed it out with a small saw and nippers. Not wanting to finish the hole, but just hog out most of the material I left a margin for error. The rest of the hole I did with a drum sander. A rotary tool makes quick work of plastic like this and your hole can easily get out of round. Fixating on shape alone can lead to problems, as by the time the hole is rounded out again it may be too large. Patience and working in small steps will keep you on the right track. Check your fit often. If your hole gets to big you can always apply filler and try again.
Now is also the time to drill the hole for the laser. I chose to put mine near the A/B buttons under the main barrel.
Step 5: Solder and Hot Glue
Video of electronics test:
Now that you know everything works you might want to take this opportunity to break out your hot melt glue gun. Hot glue is an easy way to add strain relief to your spotty solder joints. You never want a solder joint bearing load or taking regular movement as a broken connection at DragonCon might ruin your whole weekend.
Remember, liberal application of hot glue isn't just for crafters and cub scouts.
Step 6: Painting Teh Wood
Painting might sound hard but its really the easiest and most accessible part of this whole project. You going to need 4 cans of spray paint, a 1 inch brush and a paper towel. I get the store brand paint from the OSH near my house. You always want to get all the same brand of paint so you know they are chemically compatible. You will need Black Primer, Red Primer, Colonial Red and Silver. The brush should be a cheap one, your going to end up ruining it.
Before any painting you're going to want to go over the WHOLE gun with sand paper. The 100 grit you used earlier will do nicely. Simply, you're removing the gloss finish of the plastic so the paint will stick, but this is also an opportune time to distress any more of the exterior for a more worn look. Rounding corners, removing seams and removing textures should be done now.
Apply several light coats of black primer to the whole gun. Rotate the project 90 degrees between each coat to ensure the primer gets everywhere, in all the cracks, crevices and other tight spots. This is a LIGHT application, don't add more then a dusting on each pass, letting each dry 10-15 min between coats.
Next, spray the gun grip with red primer. My red primer is almost brown. Don't worry if you get some on the parts that will be metal, concentrate on the wood. If you run a dry paintbrush through the wet primer you'll develop striations that will enhance the wood grain texture later on. After a brief drying time apply a light coating of colonial red, and brush again. Alternately spray the red and brown several times until the desired texture and colour has been reached. Close up the texture will be lifelike, but from a distance the effect is less then stunning. For more realistic effects at a distance we're going to need some shadows. At this point join the two halves of your gun. It will look better if the highlights run right over the seams.
Apply a generous amount of the paint in a single spot on a palate, newspaper or magazine, etc. Using just the tips of the bristles dry brush some colonial red down the length of the grip. Your just adding highlights so liberal application is not advisable. After the red has dried do the same with black, these shadows will add depth when seen from a distance. Any closer than arms length and it'll look like paint but from far way - you're solid! Plus, you dont want to get that close to anyone at comic con anyways.
Step 7: Painting Metal
This next painting step is by far the MOST fun and most messy.
First tape off the entire grip of your prop gun. You don't want flecks of silver all over your freshly fresh wood grains. As long at the paint's had 30 min to set up, blue painters tape should work. Invest in painters tape, its just sticky enough and you can get it anywhere. Next apply several light coats of silver from different angles, allowing each one several min. to set up between coats. Its very important that this silver coat set up EXTREMELY well before the next step.
Have a paper towel ready, wad it up into a crinkly ball so its ready to get into little cracks. Once the last silver coat's been dry for 30 min apply a heavy coat of black over half of the gun body. Just go crazy, let it run and get into all the cracks. If you don't put on enough, the paint will dry before you're able to wipe most of it off. Try to wipe in one direction, along the length of the barrel. This step is very forgiving if you work quickly and apply lots of paint. Spray paint has solvents that keep it wet in the can, help it stick when sprayed and allow it to dry quickly. If you doddle, the solvents will melt the silver coat underneath so it wipes off with the black; OR the black might dry a little and form dots that just smear. By using a lot and wiping fast you get a dirty silver on the high spots and black gunk in the low spots.
Try this several times if you have to. It's hard to do right the first time but the learning curve is fast. Make sure you don't forget sections or accidentally over spray when adding a fresh coat. Ive hung mine from the grip with string so I could do the whole piece at once and not have to set it down to dry.
Step 8: Alls Well
The laser diode is the only part that needs really precise alignment. I built up a base with hot glue then added one last drop before I set the laser in place. This means I only had a little pliable glue to work with and I could make small adjustments easily. I arbitrarily set my dot to line up with the sites at 6-8 ft. Do it where ever you want, i like 6 ft.
You can use this opportunity to tack down any of the longer wires to the inside of the gun. You do not want wires banging around inside this project. If a stray wire get jammed into the trigger mechanism your game of Vampire the Masquerade could be terribly delayed while you diagnose the problem.
Now that everything's in place screw the gun together and give it a feel. Does the weight feel good? I put my batteries right over the trigger. Thats comfortable for me, but maybe you need to glue in some lead by the hammer? Give it a shake, anything loose? Loose parts need to be secured. If EVERYTHING is the way you want it, open the gun up and add little drops of super glue to all the lights and flashlight switch. The hot glue's great for testing but super glue bonds plastic more permanently for when your actor gets upset and throws his prop at the sound guy. Don't go crazy with the crazyglue (lolz) but use enough to make a more then tenuous connection.
Now screw everything together again and get some fresh air you otaku.