Gas adjustment screw for FNAR piston chamber (cylinder)?

[Bill_Rights]

In another thread, HexOrd mentioned to a propective FNAR buyer:

I was not aware of the gas adjust screw for the piston chamber and therefore the rifle did not act like a semi-auto.

.

I am not aware of this adjustment screw either! I just re-reviewed the User Manual for my FNAR, and I don't see any mention of such a screw or adjustment.

What gives?

[SgtStrykerUSMC43]

If you look at the front of your rifle's handgaurd, you'll notice a phillips head screw. I think that's it. I'm not sure because I don't own (want) one. Not that I don't like the concept. It just doesn't have a place in my tool box.


PEACE THROUGH STRENGTH

Edit: Here's a link for the photo of the screw:

http://fnforum.net/viewtopic.php?t=12208

[Hraefen]

That Screw on the Handguard justs hold the handguard on. The gas block and piston are within. The screw does thread into the front of the gas block but does not adjust anything. Removing it enables access to all the moving mass of the gas system, its short stroke piston, spring and rails. All the fouling stay in here and usually lands on the plastic fore arm cover.

I did not see an adjustment screw ala Sig556, Scar, and other high end milspec carbines. But I'll take a look again. My xm15/ak does not either. THis gun as concieved is to be more an SASS riffle then a zombie gun. As I understand it the adjustment screw on the gas block is for when you fire so many rounds you need to adjust after extreme fouling. Just to keep you going.

Have not been back to the range to shoot....range work ongoing on my days off.

Check out this link for a report and detailed photos.

http://gunblast.com/FN-AR.htm

[SgtStrykerUSMC43]

Thanks for clarifying the screw. As I stated I wasn't sure because I don't have or want one.

The FNAR is a modified BAR (Hunting rifle)



PEACE THROUGH STRENGTH

[Bill_Rights]

Hraefen,

Thanks. Please look again and let us know what you find. I think you are at least partially correct about the gas adjustment screw on MBRs (main battle rifles) - get dragged through dust, can't clean it when you need to? adjust screw until the action cycles again. Pray some more.

I agree, the FNAR is more of an M110 SASS type design, but really it is not up to that standard and I did not expect it to be.

The FNAR is a police/SWAT-grade DMR (designated marksman rifle), not intended for long-range sniper use, though could do in a pinch. As such, it is intended to spend most of its life strapped to the floor of the trunk of a police car (or the armor rack of a SWAT van). Not dragged through the mud.

The OTHER ASPECT of a gas adjustment screw is to account for the different powder and bullet loadings found in the .308 Win family of ammo. One of the great things about .308 Win is that, by changing the ammo you feed it, you can make your rifle into a varmint gun all the way up to at least a moose gun (and some would say large, dangerous game gun). Also, you can get subsonic rounds for (suppressor, obviously, but also) interior home defense. Bullet weights range from 100 to 200+ grains. There are semi-magnum loadings in the same cartridge profile. Obviously, the internal pressure generated by all these different loadings being fired spans a huge range. A bolt action rifle doesn't care. That's one nice thing about a bolt gun (the ONLY one as far as I am concerned.) A semi-auto or full-auto action DOES care about internal pressure. To account for that and keep the action cycling nicely would be the other reason for the gas adjustment screw.

However, tada! I think the FNAR action is so brilliantly engineered by FN that it'll cycle just fine with all .308 loadings! No gas adjustment required.

Somebody prove me wrong. (Mind you, I am referring to cycling with varying internal pressures only, not ammo that departs from the .308 Win spec in other ways.)

[Hex0rz]

Yes, there is a gas adjustment screw. In my case, the screw must have been overlooked in the process of manufacturing and was closed completely. I think it was closed completely atleast..

Nonetheless, its my first time owning a semi-auto and therefore could'nt tell you more on its real purpose besides the fact that it is a port screw.

On the other hand, my 30+ year experienced gunsmith said the screw is designated to adjust the amount of port gas for the semi-auto action.

It is a good idea to keep the screw in as much as possible only enough to operate the action. Diff. loads will affect how it operates. Although, if you were to get a weaker load cartridge and adjusted it accordingly, you will obviously be able to know from then on that any hotter loads will also cause it to work as well.

One must be careful with the adjustment though. I use WOLF .308 for mine and the first time I noticed, the action smacked the receiver. These rifles don't have buffer springs.

If you look here:

You will notice a silver colored screw on the left side of the gas block when the muzzle faces you. This is the screw to adjust the gas.

[Bill_Rights]

HexOrd,

It would be helpful if you could take a photo of that screw and post it here. Or rather, take a picture of the assembly the screw is in and point it out or verbally describe where it is in the picture.

If you haven't posted photos yet on such a forum, it is not too difficult, if you have a digital camera. If you have that, you probably have a way to "import" or "upload" photos from the camera to your computer's hard disk. Usually they are *.jpg (JPEG) files. If you can get that far, or want to, someone here or I can help you get the photo posted.

[Bill_Rights]

Somehow I did not see your photo before I posted asking for such a photo! Dang....

Anyway, thanks!

[alpha6164]

Can someone verify if the gas adjustment screw is the side silver phillips screw in the picture above or the black allen screw at the top of the gas block shown here below? I was told by someone that it is the allen screw and not the side screw. All inputs appreciated.

[alpha6164]

^^^I adjusted the side screw 1/2 turn at a time out and then in and it made no difference