FN Five Seven (Build)

About: K'NEX gun builder here at Instructables. More or less retired from the community, but I still pop in now and again.

The K'NEX FN Five-Seven is a favored build by many K'NEX gun instrucable'ers. With 7 favorites and over 800 views, it is bound to be of good quality. This set of instructions will tell you how to build this "much liked" gun, but first, lets look at some stats.


• Smooth slide
• True trigger
• Shoots 30 -35 ft.
• Looks relatively accurate
• Does not need more than one broken piece
• It is to-scale

Let's start building!

Step 1: Lower Reciever

So, this is the step to build the lower receiver, by far the longest set of pictures in this particular instruction "handbook." To build, just follow the image notes, and you should be all set.

Step 2: The Upper Receiever

The upper receiver should be a relatively easy step to do, just follow the pictures and their image notes.

Step 3: Trigger Guard and Firing Pin

Just build what you see in the pics.

Step 4: Rubber-banding the FN Five-Seven

Again, just follow the pics.

Step 5: Finished!

Now that you are done with your K'NEX FN Five-Seven, get some one slot dark grey connectors, push them up the handle, get a magazine pusher (like one you see in the pics) that uses a rubber band to push it up, and pull back the slide until the FP catches on a bullet, allow the slide to go forwards, and then pull the trigger.

2 People Made This Project!


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48 Discussions


1 year ago

How thick are the cut rods on the handle?

The Knex Inventor

3 years ago

I built this one a while ago, but I could not get it to work. The slide kept coming off. Great model though.

Doc Penguin

4 years ago

it is truely a brilliant gun
but it uses too much broken pcs.

Hey Red, I recently subbed to you, and I love your creations! They look so awesome :D

One problem I've had with this gun, however, is that it is rather unreliable and the top reciever wants to fly off. Maybe you could work to fix this in your next gun? I really like the slide idea though; It makes it feel like a real gun.

2 replies

I too had this problem, but then it didn't happen that often, so I just ignored it... maybe a rubberband may help with this case, but then cocking will be harder.


Hey Fred,

Thanks for the sub man, I am glad you appreciate my stuff! Well, if you want a better overall K'NEX pistol, you might want to try my new PMR-30. While I haven't shot it yet, I am pretty sure it will turn out better than my Five-Seven, even though it does not have a slide.

I have thought about returning to my Five-Seven before, but right now I have other things I'd like to build... XM8/M8/M8A1, AAC Honey Badger, I have a PMR-30 in progress... etc, etc.


5 years ago

Having trouble with the mag it with I cock the gun back all the bullets fly out.

1 reply

5 years ago

Nice one, Red, and as for that tan rotation lock that you said needs to be broken, it can easily be replaced with a blue cap.

14, 5:30 PM.jpg14, 5:30 PM.jpg14, 5:30 PM.jpg
7 replies

Yeah, that is a box I made to house and organize my K'nex. I didn't use what you made, as I don't have as many pieces as you, and built this a year ago, but yours and mine are sort of similar. Remember on your ible when I said I had a slightly different method? This is it. I've been planning to post it sometime, but I haven't gotten around to it. :)

Oh okay! That is a great idea! Wait a minute, I thought you had more pieces than me! (Although you do have a lot more Nerf guns than me, partly because Elite guns are yet to be launched in India.)

XD cereal? Haha, well I've been in the biz for a while now, so yeah, I have quite a collection, but when I say "Nerf," I mean Nerf, Buzzbee, and homemade guns, as well as blasters of various other origins. My pure Nerf collection is about 60. Also, having 9 guns is plenty to get the job done, often I find some of my guns covered in dust from intense disuse ;). It takes a lot to keep them all running.


5 years ago on Introduction

Nicely done Red. hmmmm wasn't this the one that TheRacker built and you told him to take the pics off or something...?