Ah, I picked up one of these not too long ago.
There was something about this gun that intrigued me.
It looks absolutely goofy. 
But it felt so comfy in my hands. 
I had to have one. :rolleyes:
So here it is as I got it from the FFL (except for the Aimpoint).
Notice that the HK-style charging-handle is on the front left.
Ejection port at the front right of the carbine.
The FS2K gently burps brass out at your feet - no flying brass!
Magwell. Out of the box, the gun does not drop mags freely - the mag release button only unlatches the mag, and it must be pulled away from the magwell.
Steyr AUG (the M4C member) mentioned later in this thread that you can remove a rubber gasket thingy to fix this.
Most people use the first joint of their index finger to push the button (upward motion) and then pull on the mag with the entire hand (downward motion).
Also, note that only GI 30 round AR/M16 mags (and 10 round mags made by FN) and larger (thanks for the correction tombirdman) work in this gun. It is impossible to get a 10 or 20 rounder in there.
PMAGS donāt fit. Neither do EMAGS, apparently (per steve-oh).
The chamber is right under your chin.
Here is the inspection cover on the top of the receiver - you can look right down into the action to inspect the chamber.
I took the guts out because I couldnāt get a clear picture.
The rifle comes apart easily with a simple push of the stripping pin, from the right side towards the left side.
The barrel receiver comes apart from the āframe.ā
Although not shown here, the barrel, the barrel receiver, and the āframeā (the plastic lower receiver) are serialized. Very typical of the Europeans.
This photo shows the modularity of this platform.
The lower handguard (all polymer) comes out.
Note the safety which is inside the trigger guard (sorry had a tough time getting closeup pics). Itās just below the trigger. A RH shooter will disengage the safety by pulling (to the right/back) with the index finger.
The safety is VERY NOISY.
Pic of barrel receiver and bolt and bolt carrier assembly.
This should look familiar to FN FNC owners.
Closeup of the bolt and bolt carrer assembly - viewed from the top.
Yes, thereās plastic in that assembly. That white piece of plastic is called the āswitch.ā
Disassembly of this group is well, IMO, a PITA.
First step is removal of the switch (that white hunk of plastic in previous post). Couldnāt get a picture of it, since removal of it is a two-handed operation. You have to push down on the rear housing return spring on the slide rod. PITA.
The second step is the firing pin. That is done by exerting upward pressure on the firing pin retaining plunger (Iām using my index finger).
To remove the bolt, I am first lifting the bolt alignment lever ā¦ and then pivoting the locking cam and removing it.
Disassembled bolt carrier assembly.
You can break the bolt down further to remove the extractor, but I aināt gonna do that today.
Does this look familiar?
Hell of a lot easier to clean this way.
View from the top - how the bolt carrier assembly fits into the barrel receiver.
Like the Steyr AUG, the FS 2K has a hammer group assembly.
To access it, first remove the butt plate.
If you were an FS2K proctologist, this is what youād see. 
That white thing in the middle (far back) is the hammer, and it is in the un-cocked position.
Hammer group assembly.
Yup, that white hunk of plastic to the left is the hammer. Lot of plastic in this thing, lol.
The hammer is cocked.
Gas piston.
Iām going to come back to this after my camera recharges.
In the meantime, hereās a pic of the tool FN provides to help remove the gas plug and the piston.
Itās called an OREA 892. I donāt know what it means in Belgish.
The basic rifle, with condiments.
The first thing youāll notice is the FN Tri-Rail system (which I ordered from Bartās Guns - thanks to all the M4C guys who chimed in for that tip). It replaces the stock hand guard.
To which Iāve added a Tango Down stubby VFG.
Troy quick detach sling mount.
Nylon sling adapter from Urban-E.R.T. Slings
Blue Force Gear VCAS, attached with a bit of jury-rigging.
Surefire 6P mounted with Weaver Quad Lock 49046
So, how does this thing shoot?
Overall, I LOVE IT.
+Accuracy is very good, although I havenāt done too much other than zero the Aimpoint at 50 yards with 62 grain Prvi Partisan .223. At 50 yards, with a LaRue/Hensoldt Po Boy 3x Magnifier behind the Aimpoint M4, I was getting 3/4 inch groups.
At 100 yards, I was having no problem dinging 10x10 steel plates, offhand.
Barrel twist is 1:7. Barrel length is 17.4 inches on models with detachable flash hider.
+The trigger pull is pretty good for a bullpup. IMO, better than a factory Steyr AUG (which sports a 9lb trigger pull IIRC). Itās still a little spongy compared to an M4.
I got a chuckle zeroing the optic. I didnāt have time to boresight, so I started off at 5 yards just to get on paper.
At some point, the bullet impact at 5 yards would not change no matter how high I dialed up the elevation. 4 clicks, nuttin, 8 clicks, no change, 12 clicks, dang, 16 clicks ā¦ no change. :mad: So then I try to see where the bullet impact is at 100 yards ā¦ no surpise, Iām high by a good measure. So I dialed the elevation down a bit, and moved the target out to 50 yards to zero from the prone position.
-A caveat: I donāt know what it is about this gun, but if your left support hand is too high up on the handguard near the gas plug, YOUR THUMB IS GONNA GET UNPLEASANTLY ZAPPED with plasma. Ow.
+I love that the brass ejection is very gentle. Right at your feet.
? Iām not sure how I feel about the mag not dropping freely. I like that feature in my M4geries. Itās a definite change in the manual of arms!
Gun doesnāt get very dirty, being a piston design, but the bolt carrier assembly is a PITA to disassemble.
The FN Tri Rail system is heavy, and pretty wide. If you are using a VFG, and want to reach your white light mounted at the 3 oāclock position, youāre gonna be stretching unless you have sasquatch-sized hands.
The safety is very noisy. Too much clicky sound.
I can see the FS2K being a nice tool for close quarters, as well as in vehicles. The LEOās that were on the line last weekend concurred with that assessment.
Iām going to putter around with this setup a little more, and run it in a class.
So far, so good!
Fantastic write-up of a fantastic gun. I sold mine to finance my M16, but man do I miss it.