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FNC 3 round burst kit and Sear Installation

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Disclaimer: this is a rescue of a post made by "Observer" before the images and text are lost. I don't recommend you modify any firearm and leave it to a professional gun smith. Only for lawful NFA registered firearms.


FNC Rifle 3 round burst kit and Sear Installation

Since questions routinely come up regarding the FNC burst

kit install I thought I'd make this available, it would be nice to have it

archived somewhere more public.

Please note:the images are all hosted on imageshack and if you don't click on them they will eventually

be deleted.

By clicking on the thumbnails you will reset the imageshack timer

and the images will continue to be available to your fellow FNC enthusiasts!


My rifle is an 18" FNC Para on a Form 4 with an S&H sear. The conversion was done by Curtis Higgins.

I had the camera warmed up tonight so I decided to take and post some detailed photos of my FNC.

This is my first time trying to use imageshack so let's hope I picked the right code to paste here and get thumbnails! (YAY! It worked!)

Side view, stock folded. I have the B+T rail mounted on mine along with a cheap eBay Aimpoint knock-off. (Hey I didn't want to look too much like Pacino).

And NO JOKES about a $60 scope on a $6000 rifle!

Anyway this particular rail prevents using the iron sights even without the red-dot sight on it. I don't know if this is also true of the FN factory version. From what I've seen it mounts a little differently with a throw-lever type system rather than a jack-screw type.

Close up of the receiver markings.

On my rifle the only markings are on the upper receiver, my understanding is that upper receiver markings can vary a great deal. You can see this little black rifle has been a world traveler.

But at least he ended up in the right place...the Heart of Dixie.


<a href="http://img527.imageshack.us/my.php?image=fncpics022qj.jpg"target="_blank"><img src="http://img527.imageshack.us/img527/570/fncpics022qj.th.jpg" border="0"></a>

Right side view...

<a href="http://img527.imageshack.us/my.php?image=fncpics035yz.jpg"target="_blank"><img src="http://img527.imageshack.us/img527/4191/fncpics035yz.th.jpg" border="0"></a>

...and close up.

<a href="http://img527.imageshack.us/my.php?image=fncpics043ub.jpg"target="_blank"><img src="http://img527.imageshack.us/img527/660/fncpics043ub.th.jpg" border="0"></a>

Here's a direct comparison with my AR. The FNC has an 18 inch barrel, the AR has a 16 inch. Just different proportions because of the way the stock folds and the buffer tube length. The FNC is amazingly compact when folded.



Two pics of the gas adjustment lever (the little triangular shaped tab directly above the rear of the handguards) . Mine is currently set at 'normal' but can be moved to the right if more 'oooomph' is needed. I've never had a reason to change it over as it already ejects quite forcibly.



Grenade launching sight (alidade) in down and up position. This blocks the gas port when activated so the action won't cycle without pulling the charging handle. According to the manual you use the V-notch to line up with the tip of the rifle grenade and the target. Sounds cool so if I can find some true grenade launching blanks I may give it a shot.



Although the FNC does not have a last shot bolt-hold open device (I don't like it but I guess they had a good reason), the bolt itself can easily be locked open by pulling the charging handle backwards and 'out' into a detent position. When you're done you can bang it back in with the heel of your hand or push it out of the detent position to close the chamber.

You can also see the dents on the front of the dust cover (the weird little spring loaded flap). As far as I can tell, these dents are from the cases being spun out 180 degrees and the mouth of the spent casing bangs into this. It leaves the case mouth with a flat edge in addition to a large crease about halfway down the case.


Believe it or not, this is as far open as the upper will tilt. What's even worse is that due to the balance and weight distribution it doesn't stay open very easily and keeps banging back down onto the lower....or worse...the machinegun sear. Luckily the push-pins that attach the upper are in the exact same relative positions as on an AR so it easily comes apart.



The arrow points to the sear. You can see how it sticks straight up when the upper is removed. Once you've opened it, you cannot close the upper without some 'tricks'. Note: To my knowledge this only applies to sear guns due to the way they're made (still very clever but it's not a factory machinegun) You can also see shiny aluminum where material has been milled away behind the magwell to fit the sear.



Below are the 'guts' of the rifle. The recoil spring assembly, gas piston, bolt and carrier group all slide easily out the back of the upper receiver once you remove the charging handle. Very nice.

(Oh and yes I realize it's very dirty....that's because I actually take it out of the safe and enjoy shooting it!)


Close up of bolt and carrier group.


Rear of the upper receiver showing the two channels that the bolt lugs ride in.


Bolt face.


Below are the bolt, firing pin spring and carrier group. The firing ping is captive in the carrier by way of a roll pin.


Hand guards removed to show the gas tube and barrel. The hand guards are very easy to remove but the little spring clip at the front will pinch the crap out of your finger if you get it caught when re-inserting them (the hand guards, not your fingers). Much easier than an AR but I wish there were some more front hand guard options besides a $400 B+T quad rail.


With the gas tube removed (I guess it's called a gas tube? Maybe gas cylinder?). This rotates to the 9 o'clock position (from shooters perspective) and pushes into the receiver before sliding out sideways.


Close-up of the front gas block.


In the below photo you can see the tiny hole that is covered when the gas adjustment is moved to the 'fouled' position. (It's on the gas block extension directly to the left of the shiny silver bolt, the gas cylinder simply rotates over to cover it.)

<a href="http://img506.imageshack.us/my.php?image=fncpics277ib.jpg"target="_blank"><img src="http://img506.imageshack.us/img506/1959/fncpics277ib.th.jpg" border="0"></a>

Flash hider, grenade launcher. Note the way the 'jets' are drilled with a forward angle.


I'm not sure why it has this pattern on the front edge of the flash hider. Maybe so you can emboss things with a pretty decorative pattern if you're just sitting around?

<a href="http://img506.imageshack.us/my.php?image=fncpics305vj.jpg"target="_blank"><img src="http://img506.imageshack.us/img506/4462/fncpics305vj.th.jpg" border="0"></a>

Here's what I mean about the machine gun sear not allowing the upper to close. It is supposed to fold forward and it fits into a slot on the underside of the bolt. In this position the bolt is closed (because you have to close it to force the recoil spring assembly into the lower. Then you stop about here and pull the bolt back about 7-10mm so the sear is allowed to fit into the slot and ride forward as the bolt locks home. So if you open up a sear gun don't just try to slam the upper closed, it won't work and may eventually screw up the fit of the sear (not likely unless you're particularly ham-fisted but why chance it?)


Hope this was informative.

If you know of any errors please let me know and I'll correct them.


Part 2 - Sear Installation

On another forum I've seen a lot of questions about the FNC 3 round burst kit and how to install it.

In fact, when I bought the kit it didn't come with any instructions and I couldn't find any pictures on the net of how all the pieces should fit together. As I found out, it's physically impossible (without bending and breaking stuff anyway) to install the kit incorrectly. The rifle simply will not fit back together if the parts aren't installed in the proper positions.

Yes....I found this out the hard way!

So in the interest of saving someone else time I've shot these photos of how to install the FNC 3 round burst kit.

The first photo is my FNC with an EOTech 511 installed (my Chinese Aimpoint clone stopped working) and most importantly...the M249 SAW grip. Look at how modernized the weapon looks with the addition of this grip, plus it's got a nice grippy, textured surface unlike the original shiny FAL-style grip and the grip angle is much more natural. If you buy an FNC this should be your first purchase.


This photo shows the EOTech mounted on the rail. Notice how high it sits, this is why I wish someone would make a railed upper for this rifle.

<a href="http://img101.imageshack.us/my.php?image=img11308ov.jpg"target="_blank"><img src="http://img101.imageshack.us/img101/2858/img11308ov.th.jpg" border=0></a>

How to install the FNC 3 rd burst:

Remove the upper receiver

<a href="http://img101.imageshack.us/my.php?image=img11313rq.jpg"target="_blank"><img src="http://img101.imageshack.us/img101/6514/img11313rq.th.jpg" border=0></a>

Rotate the selector lever to the 12 O'clock position...


...and push it through from right-to-left.


Lift the 'fake' burst pack from the rear and it will easily slide up out of the receiver. If your rifle does not have a burst pack installed, there is a small blank metal stamping in the same location that maintains the external dimensions of the real burst pack without any of the levers and springs.


Simply lift it out.


This is the mechanical portion of the pack and you can see the teeth that the pawl will lock into. Do not attempt to take this apart as it wasn't made for you to monkey with and disassemble.



Let the hammer go slowly forward to take pressure off the spring.


I'm sure someone has a better way to do this but to remove the hammer spring I use a pair of needle-nose pliers to grip the U-shaped point at the front of the spring pin that fits onto the hammer itself, then compress it and lift if up-and-out.

This seems sort of crude but I don't know a better way to do it. Any suggestions?


Once the spring is removed the hammer pin is easily pushed out, again from right-to-left. Just lift the hammer assembly out of the receiver at this point.



This next photo shows the three other critical parts of the burst system. When you buy a burst kit you should receive 4 components in total.

1-the burst pack. 2-the pawl spring. 3-the pawl pivot pin and 4-the pawl itself.

Your hammer should already have the recess for the pawl cutout and the small hole drilled for the pawl pivot pin.

The first time I put everything together I had the pawl put on wrong. It fit okay here but upon reassembly the hammer pin will not go all the way through the receiver and lock. Thus the front of the burst pack won't fit, thus you can't put the selector back in.

I was very grateful that someone at FN thought of this when designing the rifle!



The next two photos have nothing to do with the burst kit per se. But as long as I have the thing apart i thought I'd show the angles that Mr. Higgins grinds into the hammer axis when setting up the sear.

This little ledge is where the S&H sear locks up



Nothing special, just a shot of the trigger group with the hammer removed. At this point it also will simply come out by pushing the pin through the receiver. Very simple.


Ready for re-assembly.


All done!


I can't stress enough how easily everything fits together if you've done it correctly. NOTHING has to be forced and the parts almost literally 'fall' into place with no effort.

The FNC has a fairly low cyclic rate so the 3-rd burst is probably unnecessary. It's easy to get off doubles or triples without the kit installed. But I hated having a labeled 3 position on the receiver that didn't do anything, then having to explain it to people ...umm yeah that's not installed so don't put the selector there... so here we are!

The other cool thing about the FNC burst is that it resets if you don't fire the entire 3 rd string. So if you only fire 1 or 2 shots on burst, the next time you pull the trigger it will still fire the full 3 rds. <BR><BR>This is unlike the M16 which will not reset.

Hope this has been informative.


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