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Discussion Starter #1
I have been wondering if anyone has done much adjustment to their gas blocks? I was really wondering how the rifles groups would be affected if the gas was completely shut off so the action would not cycle. Part of the issue with consistency on the FNAR is the lack of a solid platform such as a pillar bedded stock or chassis. A good experiment would be to: 1. completely shut off the gas and test fire groups and then, 2: tune the gas to cycle the ammo and function of their rifle and then test fire more groups.

Some rifles (such as the AR-15, I know gas operated, not piston) are set up with the gas flow to essentially be wide open so the rifle will function with any ammunition fed to it. I do have experience tuning the AR gas system to function with a specific buffer spring and bolt weight, and I do know the rifle is much smoother cycling after tuning.

What do you guys think?
 

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I have adjusted the gas block on my FNAR, but it was not for accuracy reasons. From the factory there was too much gas, and it was causing the action to cycle too "hard" and it was banging the ejected brass against the reciever, damaging the mouth of the brass. By turning the screw in, it restricted the amount of gas, slowing down the cycling of the action. I found the gun to have a softer recoil as a result, so I am sure that the groups got better, but I did not really keep track. I was also working on my handload development at the time, so groups were not always consistant because of the various loads I was testing. Once I got a load that was 1 moa on a regular basis, I made a final adjustment to the gas block so that it would just cycle the action. I use Varget for powder which is fairly consistent in a wide range of temps, but at the extremes I sometimes make small adjustments to the gas block. Last week I was out shooting in -2 F temps, and have been out in as warm as 95 F. I use my FNAR for hunting as well as pleasure shooting, so I make sure I do a test shoot a week or so before season when the temps are in the general area of what is expected during the hunting season. So far I have taken 3 black bear and 4 white tail with the FNAR, and none of them have taken more than 1 shot. It might not make a 1 MOA group every time (most likely because of the shooter), but it is more than accurate enough for hunting purposes. Tuning the gas system for your particular load is a good idea in my opinion.
 

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Discussion Starter #4
Thanks kmiles! I noticed my brass being damaged and I didn't think about the gas block. Great information! :?
Same here on the bent brass.

Gas adjustments and experiments coming when I get a chance.

Thanks kmiles.
 

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Guys, I had brass where the mouths were in the shape of "D", and the base of the brass had a round ejector mark. OPENING the gas screw fixed that, (Counter Clockwise), can't remember how much, because I turned the gas screw IN first based on internet advice and things got worse. Maybe it ended up 1/2 a turn backed out from factory, but run your own tests. then tighten set screw. Got this advice from a retired military guy out on the shooting range. call FN for advice. CYA. It likes 168 grain BT
 

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My positive experience is similar to Jeff, Dal and kmiles with gas adjustments. I was able to turn down the gas and stop the D mouth with a noticeable reduction in recoil and no impact on accuracy. This is back when I was getting 200 yard ` MOA groups with handloaded 150 gr Sierra Game Kings. I still have work to do on accuracy, but adjusting the gas is a good idea IMHO. Note, however, that the manual recommends not messing with the gas block and there are different opinions on which screw to move (The silver one at an angle is what made a difference for me).
 

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Discussion Starter #8
I'm experiencing the same condition with marks and dented brass. I'm hoping to have time to make some adjustments at the range tomorrow.
Hey Wrencher, let us know how the adjustments worked out.

If you have any idea how may turns etc., that would be good info too.
 

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When I started turning mine in, I started with a 1/2 turn. From the factory mine was about 1 3/4 turns from bottoming out. With the fine adjustments I ended up between 1/2 and 3/4 in from where it was at the factory, or just over a full turn from bottoming out. If you turn it in too far, the gun will fail to cycle on its own. All you do then is turn it back out 1/4 a turn at a time until the gun cycles. I am using 39.8 gr. of Varget over a variety of 168 and 175 bullets. There will be differences with ammo and outside temps, so I make sure I always have the tools to make adjustments if there is a change in ammo or a large change in temperatures from the last time I used my FNAR.
 

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EDIT:

I thought of a simpler way to address this, in the form of a question, since the posts here seem to contradict.

So, are you saying "turn the screw clockwise to SLOW the action, soften recoil and reduce brass damage"?

OR, turn it ANTI-clockwise to slow the action, soften recoil and reduce brass damage??
 

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I turned mine down 3/4 turn and it stopped running. Opened up to 5/8 turn down and it has run everything from ZQI to Hornady Superformance. It had no troubles to start with, but turning it down reduced the recoil slightly with no side effects.
 
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