Well, this is the instructable for the third of the "Knex Heavy Cannon" line.

Anyway, this cannon is quite similar to the v2 in many ways. The differences are that the bow is smaller, the barrel slides are shorter, smaller and more piece efficient, and the trigger is a tad smaller, there are no wheels on the back (they are still on the front, though), and I got rid of a few unneccasairy bits. Range is 70-80 feet.

I hope you all like it! Feel free to ask any questions.

Enjoy!

I have made a few other versions of this gun. Check them out!
Original
Mini
Micro
Handheld

Step 1: Parts List

This is where you will find out whether you have the pieces to make my cannon. I hope you gots the pieces!

FOR THE CANNON
Rods
Green-----314
White------174
Blue-------131
Yellow----35 (If you have one, you can use one gold)
Red-------36

Connectors
Dark Grey--90
Light Grey--8
Red---------76
Green------81
Yellow-----148
Orange----43
White-------23
Purple 3D--147
Blue 3D----59

Other
#64 Elastics------20
Y Connector-----6
Tan Clip-----------3
Blue Spacer-----84
Silver Spacer---26
Grey wheel (as seen in photo) - 8

FOR THE AMMO
Rods
Green---14
White----6

Connectors
Red----3
Green-4
Purple-2
Blue---3

Step 2: Wheel Base

This is the wheel base. Yes, this one has wheels also. IF you don't have the pieces for the wheels, feel free to improvise. You could easily put a base like the one off of the v1, that uses more just yellow and red rods.

1: The part you shall make first.
2: Lets start with the wheels themselves
3: Make these two panels
4: Make all 8 of these things
5: Cross-snap one into place as shown
6: See how that grey connector should look
7: Put the rest on it the same fashion to get a wheel
8: Repeat steps 3-7 to get a second wheel
9: Make these two buddys
10: Also make these supports
11: Put the blue rod through the yellow connector like so
12: Put the other part of that thing on the other end of the blue rod
13: Make this part. It is the axle
14: Slip one wheel over each rod
15: Add the spacers shown
16: Put one of the supports on
17: Put another spacer on and cap it off with a tan clip
18: Do so on both sides to get this
19: Put the big support in the center like so
20: Close up of that
21: Finished wheel base

Your on a roll! (pun intended)

Lets crack on, shall we?

Step 3: Bow

This is one of the longer steps. Make sure to put in all the spacers, and be sure that all horizontal supports are in before you use it. It is easy to miss clipping in a few :-(

1: The bow. Yay!
2: Start with the lower bow. Pretty easy.
3: Close up of the side
4: Close up of the middle
5: Close up of the end
6: That whole part upside down
7: Close up of the middle of that
8: The front up close.
9: Make these two things. Neat!
10: Closer of that apparatus
11: Thats a white in the middle
12: Close up of the end
13: The whole thing again
14: Make a mirror copy of that
15: Make Make this. it is the upper barrel
16: At a angle so you can see the rods
17: Upside down
18: Close up of the side
19: And of the middle
20: Close up of the end
21: Slip those apparatus over the rods like so
22: What it should look like from the side
23: Do so on both sides
24: You need to string the bow now. Its easiest now. Later on, the top of the bow will get in the way so, do it now!
These are the kind of elastics you will use. They are #64, the standard thick ones
25: Place two elastics on the floor or table like this
26: Pull the one through so it looks like this
27: Now pull the other one through so it looks like this
28: Pull tight
29: Now put another one on the end
30: Pull the knotted elastic through
31: Pull the new elastic through and tighten
32: Put two more on to get a string of 5. Now make three more, so you have four strings of 5
33: Pull the elastic through like so
34: Pull it over to the connector shown. You will have to take it apart to put the elastic over it
35: Put it around the rod like so
36: Put a second string around so it looks like this
37: Put both strings on the bottom wheel so it looks like this
38: Put it through on the other side so it looks like this
39: Put the other two elastic strings on the top wheels and hook them in the same way, except above the connector
40: Now put the top bow on like so. Be sure to clip in all the side panel thingys
41: The elastics should look like this now
42: This shows you how you can access the wheels
43: Simply pull the red connectors down
44: Finished bow!

YAY!

Step 4: Upper Barrel

This is the upper barrel. I did not take this piece of the gun apart, so the pictures are just of the upper barrel as a whole. I think it should be pretty easy to follow. Have fun!

1: That part in question
2: Close up of the front
3: The front from the side
4: The other end. Make sure to get all the grey connectors inbetween the red connectors
5: From the back
6: Another view of the back (sorry aboot the blur)
7: Top view of a joint. Most of them should look like this
8: That from the side. Remember the spacers!
9: Urg.. What a eyesore. Anyway, thats it upside down
10: The other end upside down
11: Finished Upper Barrel. Yayz!

Step 5: Lower Barrel

This is the lower barrel. It is almost identical to the upper. (Actually, it might be identical. Why am I making another step for it?!?)

Ok, lets get to it.

1: The barrel. Look at it with all its barrelikness...
2: The far end
3: What the middle sections look like. Notice that there are only two lines of red rods on top, as opposed to three on the upper barrel
4: The far end upside down
5: What the joints look like. Remember the spacers!
6: The other end
7: Closer up of that other end
8: The other end from the end of the end.
9: The other end from the end of the end upside down
10: What the joints look like upside down
11: Your barrel. Whoop whoop!

Step 6: Rear Mechanism

This is a long, boring and monotonous step. Enjoy!

1: What you are about to make
2: Lets start with this big 'ol knob
3: Make this part first. If you have one, use a gold rod, but if you don't have one, just use a yellow
4: That part upside down
5: Another view of that little piece
6: Make this part. Its 10 greens, just so you know.
7: Make this part as well
8: That part from the side
9: That part upside down
10: Attach the piece with the rod to the bit you just made like so
11: Clip the greens on top as shown
12: That whole assembley upside down. Set it aside for now
13: Make these two bits, and put them aside also
14: Build those two parts
15: Put them together to get this
16: Make this little piece and put it aside to put on later
17: Make this little plate thingy. It will go on the bottom
18: Build these four pieces
19: Make these two bits. Rotate the connectors circled to be like the ones on the left
20: Those pieces from the back
21: Make these two pieces
22: Make this guy
23: Make this. It is the main barrel of the trigger mechanism
24: That Last piece from straight on
25: That last piece from the other side
26: Close up of the top
27: Looking down from straight above
28 That whole apparatus on its side
29: Slide that panel you made before into the slot so it looks like this
30: Now it should look like this from the back
31: Put a blue rod down the slots shown
32: Slip one of those pieces you made before over the white connector so it looks like so
33: Put that bit you made before over like so. attach it to the red rods
34: From the side
35: Now do the same to the other end
36: Put the other piece you made before over the neck like so
37: It should now look like this
38: Put a red rod on the back like so
39: Put a spacer over each red rod
40: Now cross-snap two of those bits to the red rods like so
41: What it should look like from straight on
42: Now do the same to the other side with the other two pieces so it looks like this
43: Put that panel thing on the bottom like so. Attach things that look like they should attach
44: From straight on. Make sure the blue spacers go in inbetween the grey and red connectors
45: Put that little apparatus that you made earlier on top
46: Put that tiny piece you made before in as shown
47: Put the knob on top like so
48: Just showing you that the yellow rod goes through the hole in the red connector
49: To finish, place those two bar thingys the way I show you
50: A close up of that. The one on top will look the same
51: YAY! Finished trigger.

Well done! Give yourself a pat on the back and go have a nap.

Step 7: Scope/Sight

This is the sight. It sucks... Sort of. Its not terrible. It works, and looks ok, so thats good enough, right? The main reason I put it on was just to have something on top. Lets get to it!

1: The scope. Cool, 'aint it?
2: Start with this little guy
3: That same piece from above
4: Make these two. You will put them on in a moment
5: Make these. Put them aside as well
6: Make these two bits
7: Build these four pieces
8: Attach the yellow rod thingys to the two red connectors
9: Put the other bits you made a while back on like so
10: Put those four blue rods on the bottom like so
11: Finished scope.

You've got your sights on the finish. HAHAHAHAHAHA!

Step 8: Assembley

This is by far the funnest step. I think it should be relatively self explanatory. Have fun!

1: Exploded view. These are all the parts you should have.
2: Start by attaching the wheel base to the bow. Everything should line up nice and neat.
3: Close up of that attachment
4: Put the lower barrel on. Easy!
5: Close up of that connection
6: Put the upper barrel. The connection is the same as the lower barrel, so we don't need a close up.
7: Put the trigger on
8: Close up of that
9: Put the scope on like so. Make sure to not push any of the blue rods through the top of the bow
10: I forgot to say, but put a green connector on the end as shown
11: Slip a elastic band over the red connector on the barrel and the orange connector on the trigger knob. It should not pull hard, just enough to pull the knob back into place when pulled.
12: Assembley? Check!

Well done! Lets fire it!

Step 9: Ammo, Loading and Firing

Now its time to learn how to load your cannon. Its pretty easy once you have got the hang of it. I have used it a lot, and can load in about 10 seconds. Be sure everything is as I say it should.

1: Start my making these parts
2: Put the two on either side
3: And put the other two on the top and bottom. Now you have ammo!
4: Here is your cannon
5: Grab the bottom two strings (the ones on the lower wheel) and pull them back like so
6: Pull it all the way to the back and latch it onto the red rod at the back
7: Close up of what that should look like
8: Pull the other two strings back and hook them around the top red rod the way you did the lower one.
9: It should look like this at the back now
10: Take your ammo and slide it down the front
11: Slide the ammo to the back of the gun. Pull back the knob on top, so that the rod moves out of the way.
12: Slide the back of the ammo into the now vacated spot in the trigger and let go of the knob. You may have to push and shove the ammo around a bit. you need to push the rod through the hole in the back of the connector on the ammo. Once its through, make sure that the rod is going through the trigger barrel all the way. (Pant)
13: Now take the elastic strings and slip them onto the ammo like so
14: Take aim!
15: Pull the knob back. You have just fired!

YAY! Now you know how to shoot your cannon. Have fun!

I added a video of the whole loading process.