This is the assault rifle that i made.it looks a bit like an AK47 but its my own. It was originally based on killer~safe crackers monster pistol but i changed it over the coarse of a week and it became this beautiful weapon. It also uses a slightly modded version of his curved mag
Here are the Pros and Cons of the gun

Pros: good range for a mag fed gun (25-50ft depending on rubber bands)
very powerful
SEXY
10 or 12 round magazine

Cons: the bullet spins a bit decreasing its range and accuracy slightly
a little big and heavy (not good for maneuverability in battle)
too sexy to stare at for long periods of time

here is an awesome video made by matsermetsuiker www.instructables.com/id/knex-rifle-6/

Step 1: Body

this might get a bit tricky if you don't look closely.

Step 2: Handle

very easy and if you want you can use medical or duct tape for more comfort.

Step 3: Stock

make. self explanitory

Step 4: Magazine

both the curved and the strait ones are good but you should use the strait one in close combat because it holds 4 more bullets and it is much more reliable and the curved one in multi floored combat situations just in case you need to use the bipod since it doesn't have the rod sticking out. just build it from what you can see, its not really in order but the curved mag is first.