Here's my knex shotgun I made recently.
Limit of bands.
Trigger some times jams.
Uses 3 cut rods.
Step 1: The Block
This is the barrel, I think you could do it pretty easily.
1.What your making.
2.Bulid this block(i recommend to put the yellow rods in first then the red rods).
6.Make/ gather these.
7.Add them on to the block.
8.Add the yellow connector and 2 gray spacers and connect them.
9.Make/ gather these.
10.Put them in place.
11.Start sliding it on.
14.Put them together.
15.Put them together.
16.Add onto the block.
17.The ram you need tape like the bottom one.
18.Make the bottom rod and put it together.
19.Add onto the block.
20.Finished with the block.
Step 2: The Middle Part
This is the middle part, it is a little confusing so pay very close attention to everything.
Step 3: Handle and Trigger Part
This is the handle and trigger part, this might be a little confusing so read the image notes.
Step 4: Pump and Pin Rubber Bands
This step will show you how to put on the pump and the rubber bands for it.
Step 5: The Mags
This will show you the mags for this gun.
Step 6: The Stocks
These are the stocks I made for the gun, you can make them, or you can make your own.