I've created not the best but a powerful crossbow with what i think is a new system to fire the ammo. The range is totally dependant upon the elastic that you use and how new your knex pieces are. The accuracy is also dependent on how new your knex pieces are. My particular crossbow has a range of around 50ft with moderate accuracy. The crossbow has a true trigger and although the crossbow below has no stock i have created one later in the instructions.

This is my first instructable so please constructive criticism only.

Ps I'm not reliable for what you do with this crossbow!!!

Step 1: Create the Firing Pin.

Probably the simplest of all steps the firing pin. It is made of:

-2 blue rods
-1 red rod
-1 orange ladder
-1 yellow half moon
-and a Y shape black connector

The firing pin works because a grey or black rod (the ammo) clips loosly into the black Y connector, when it is stopped abruptly the rod keeps going. I also tried other pieces instead of the black Y though they didn't work as well.

Step 2: Create the Bow Sides.

The Bow limbs on my crossbow are reasonalbly strong. As with any crossbow you will need to make both sides and so therefore two limbs. On each limb there are two parts with a blue rod and 8 blue spacers between them. At the end of the limb where the elastic attaches there are wheels to spread the power evenly across both limbs etc.

pic 1- make 2 of these and attach two of the lower parts,not the blue rods and spacers and attach it on top. (see pic 6)
pic 2- Make this part, it has 3 blue spacers on either side and a grey 2 clip piecs after that too.
pic 3-Attach the wheel part on here, at the end of the limb.
pic 4-Same as pic 3
Pic 5- The finished limb. You will need two of these.

Step 3: Make These Pieces.

Make the pieces shown in the pictures below. They are mainly dacarotive and strenghening pieces.

pic 1- Make this piece which will attach to the back of the barrel.
pic 2-Make this piece for the front attachments to the limbs and barrel.
pic 3- Make this piece though you will need to have it as two pieces, or two halfs.
pic 4- Same as pic 1
pic 5- Same as pic 3
pic 6- make this p

Step 4: Creating the Barrel.

The barrel is the working part of the crossbow. My barrel has the same sort of designs as Fausts asult rifle. On my barrel there is also the trigger. It has a true trigger and is effective using only 1 set of elastic bands. The barrel is 13 orange ladder connecters long with one half moon connecter at the back. (see pic 5)

pic 1-Create the barrel using 2 halfmoon connecter or fullmoon connecters and a white rod and a ladder, or for the last part a halfmoon connector. then attact together. Also add the rods that i have shhown.
pic 2- Another picture of the barrel this time side on.
pic 3- The trigger is at the back of the barrel like so.
pic 4- Another picture of the trigger.
pic 5- Make sure that the last connection has a half moon rather than a ladder.

Step 5: Putting Parts Together.

Now we have all the parts we can put it together. First take the part dominated with red rods and attach it on to the barrel at the first white connector. As well as at the front orange connector. Now take the square sort of part and split it like this. To the underside attach one of the pieces that you made earlierwith yellow rods. Now take the upper pieces aslot he yellow connectors on to the yelow rods. now you can attach the under side ot the upper side and you should have a box like shape around your barrel. you will also fin that the opposite end of you under side should slot on to the half moon connector nicely.

Step 6: Attaching the Limbs

You attach the limbs to the red rods at the front of the barrel on the very fron two re rods and the ones it then falls on to appropriatly. You can now slot the firing pin in to the barrel with the orange ladder and Y running along the base. You should have finnished my cross bow assides from elastics.

Step 7: Adding the Elastics and Firing the Crossbow

First make a chain of your elastic bands and attach them to the blue rods on either at the end of the limb making sure that the elastic runs cleary over the back of the firing pin meaning is you try to pull back the firing pin you should feel resistance.

Now you must add elastics that pull the trigger away from you, th power of this must be greater than the power of the elastic that you stretched between the limbs or the trigger will not work.

To fire you must slide a grey rod up the barrel from the front then you must push it in to the Y connecter, a small click means it is attached. now pull back the elastic across the two green connecters and pull back the firing pin to the blue rod across the barrel. You crossbow is primed and ready to shoot when you pull the trigger.

Smurfer.

Step 8: Extras

Having finished all of the previous steps you have made my orriginal crossbow. Like i said earlier in the instructions this step is extras such as the stock and updates. Within the week i will hopefully of added a stock and i am working on increasing the overall power of the cross bow. I am searching for the best form of elastic for use in this cross bow and i'm considering adding a crank for the draw rather than the use of fingers.

31st August.
Since then...
-I have found that a quick elastic rather than the mos powerful you can find is the best though a mixture is also highly suitable.
-Also i have found that instead of a firing pin you can have a rod attached to a ladder and put over the drawn elastic. This maxamises the range of the cross bow with mine averaging around 60 ft though it's consitensy and accuracy is thouroughly depleted by taking this approach.

Smurfer.

Step 9: The Stock

The stock on my particular crossbow is one the slides both above and below the shoulder meaning it gives you a good resting position as well as comfort. It is relativly simple to make and attaches to the crossbow. So...

pic 1- Start off by removing this part from the crossbow.
pic 2- Now build this part, the white rod has a tan connector where the note is to hold it straight.
pic 3- Build this part as well, pretty self explanatory.
pic 4- Take the part you built in pic 3 and attach it to the part in pic 1 on to the yellow halfmoon pieces as shown.
pic 5- Now attach the part in pic 2 to the white connector and push the red rods hard dow so they rest on the connector as well.
pic 6- Now build and collect these parts.
pic 7- Attach the piece on to the part already made where shown. (sorry for the blurriness.)
pic 8- Now slide a red rod up the hole in the yellow connectors on the other part.
pic 9- Attach the red rod on to the part attached in pic 7.
pic 10- Take the tan clip and clip it on the red rod and slide it in to the yellow connector.
pic 11- The finished stock ready to be attached to the cross bow again.