Hey everyone, sorry for the half finished instructable. School has been keeping me pretty busy, and I'm hoping to finish this up and post it at a later date. This really is intended to be an idea starter more than it is intended to be a specific step by step instructable. I hope you all enjoy, and good luck!

Step 1: Getting the Basic Shape

This entire project utilizes the primitive shapes in 123D Design. Some are modified to acquire a unique shape, such as the magazine. The first step is to make a long block about the size you want the body of the rifle to be. I made mine 18 inches long and about 3 inches wide and tall. Then insert a cylinder into the block so you can keep the orientation straight during manipulations. REMEMBER, the final result is going to be larger than the model you make, so make your model smaller than the desired final size.

Next I put in the magazine, because lets face it, it'll look like a rifle no matter what as long as it has a cool looking magazine sticking out. The first step for this was to use the L-shape. Play with the thickness, width and length until you get an L-shape that is about as wide as you want the final magazine to be and not quite as long. Use the "Tweak" feature to elongate the shape some, increasing the 90 degree angle to somewhere about 130 degrees. Then use the "Fillet" tool to round the inside and outside of the now V-shape. It'll take a little bit of experimenting, but you should end up with something that resembles a magazine.

Once you have the basic shape of the magazine, rotate it and move it into the center bottom of your rifle body, and at this point it's already starting to look like a rifle!

Step 2: The Handle

The handle is super easy, just make a block about the size you want. I gripped a ruler to see how long it should be and then guessed what a good width would be. Once you have the shape you can either angle it like I did, or keep it straight up and down. Once you have the orientation you want just intersect it with the rifle body. The snap feature is really helpful for this when trying to align the handle into the center of the body.

Step 3: Adding Features

So far we've put together a body, magazine, barrel, and handle. That's all we really need, but it'll look better if we add some things here and there. I basically decided to put a forward grip, some aesthetic block on the top, and a trigger with cover. After adding these it really does start to look a lot better. You can add whatever features you want, but try to keep in mind that you'll have a chance to add details later on.

Decorative block: I added a block, the same width as the body, to the top of the rifle and then rounded its corners, just to give substance to the body.

Trigger cover: For the trigger cover I used "C-shape" that I used to "Tweak" feature to skew a little bit. Then I rotated it and intersected it with the handle and body.

Forward Grip: The forward grip was nothing more than a block I put over the bottom of the barrel and then added fillets to. Once again to get an idea of the size I gripped a ruler to see how long it should be.

Trigger: To make the trigger, I took an "L-shape" and skewed it with the "Tweak" feature. Then I added fillets on the inside and outside corners. (Adding the trigger was purely for fun and demonstrative purposes. When assembling the cardboard, the shape of the trigger won't be maintained. The trigger will have to be part of the detail work after the basic shape has been assembled)

Step 4: Dressing It Up

The last step in 123D Design was to clean up some of the edges. I added chamfers and fillets around the edges to round off corners and make the whole thing look a little neater. Having less material should also help later, when fabricating the rifle.

Once you've done any tweaking you want to do, you're done with the 123D Design portion of the tutorial!

Step 5: Design Template

The next step is to get a template so that you can build the rifle shape out of cardboard. 123D Make takes your 3D model and slices it into a bunch of pieces that can be cut out of cardboard. You just have to open the model in 123D Make and it'll create a template that you can print out, trace onto cardboard, cut out, and then paste together. The end result should be a rough shape of your rifle! (Pretty cool huh?)

*Note* The barrel is only intended to help with the design process. A cardboard barrel isn't going to work very well. If you want to use one, go for it, but I'm going to cut off the cardboard barrel, and insert pvc pipe instead.

Step 6: To Be Continued...

Well hopefully I managed to give you guys a good start to a project. Sadly I haven't found the time to put the model together. However, if you're still wanting to continue with the project I'll give you a quick rundown of what the rest of the tutorial will be, once I've completed the project.

Step 1: Insert the barrel. I want the barrel to be more rigid than cardboard, so I plan on cutting out the cardboard barrel and inserting pvc pipe into the cardboard body.

Step 2: Smooth out the edges. Take some clay or putty or bondo, or whatever you have lying around that might work, and coat the cardboard with it. This is intended to fill in the "steps" between each layer of cardboard so that the shape is smooth and rounded.

Step 3: Add details. Next use the clay to add some knobs and switches. The small details couldn't be made with cardboard (or at least not easily), so we'll utilize our clay instead.

Step 4: Paint! Use whatever paint you have. I'm planning on using spray paint for a base coat, and then using brushes to add details, such as a logo and switch covers etc.

Step 5: Enjoy it! Go use it in a movie, go trick or treating with it, or give it to a friend. Just don't get into trouble with it!

Sorry I couldn't finish the instructable yet. I hope I was able to give somebody a good starting point. Enjoy!