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Posted: 2/26/2006 6:53:20 AM EDT
This is a statement I read. The author is unknown to me. Its from a carbine course summary. Is this true. I have always been told in the military and LE to always make sure the rings are staggered. What is your opinion and should this be done or not, or does it matter.

"The gas rings do not need to be staggered, a myth that is now accepted as fact. A good gun will run fine with one gas ring."
Link Posted: 2/26/2006 6:57:28 AM EDT
It is true that the gas rings don't have to be staggered. If the rifle malfunctions when the gaps are aligned, then there is a bigger problem with the rifle.
Link Posted: 2/26/2006 7:04:39 AM EDT
An ar in correct working order does not care how the rings are.

Link Posted: 2/26/2006 7:09:23 AM EDT
Yep, those rings wont stay where you put them anyway.
Link Posted: 2/26/2006 4:50:02 PM EDT
The military teaches that you should stagger the rings. I've never shot it without staggering the rings so I don't know. Someone needs to try. I would but I now use the McFarland ring and don't worry about it
Link Posted: 2/26/2006 4:52:47 PM EDT
I spent 4 years in the Marines and never heard of staggering the gas rings.
Link Posted: 2/26/2006 5:03:54 PM EDT

Originally Posted By ColtRifle:
The military teaches that you should stagger the rings. I've never shot it without staggering the rings so I don't know. Someone needs to try. I would but I now use the McFarland ring and don't worry about it



Mfr: FULTON ARMORY
AR-15 MCFARLANDTM BOLT GAS RING
Stops Gas Leaks & Eliminates Sluggish Bolt Performance
Single spiral of spring steel loops around the bolt three times and leaves no path for gas leakage. Replaces conventional three-piece “piston ring”-style sets that can accidentally line up, causing a major leak from the gas expansion chamber in the carrier.
SPECS: Polished spring steel.

Interesting concept since most believe it does not matter or effect performance of the rifle; if the rings are lined up or not.

Link Posted: 2/26/2006 5:36:29 PM EDT
I was taught that I needed to staggar the rings in the military. It even states that in my operators manuel ( I believe ) ... But from my own experiance, they do not need to be staggard and they will spin and shift as you fire it anyhow. .... Wardawg
Link Posted: 2/26/2006 5:50:34 PM EDT
Ie never once verified how my gas rings were situated.
Link Posted: 2/26/2006 5:54:01 PM EDT
[Last Edit: 2/26/2006 6:09:28 PM EDT by Yojimbo]
I've tested this and shot my carbines with the gaps on the gas rings all lined up and it made no difference. A properly built and functioning AR will not have any issues with the gas ring gaps being lined up.

Once the bolt is inserted to the carrier the rings are compressed and gaps are basically closed.

Besides, when the AR is fired and bolt group is working the gas rings move around all over the place and won't stay in the same place you put them...
Link Posted: 2/27/2006 9:43:39 AM EDT
The fact that gas piston uppers work is proof that the gas rings do not need to be aligned. Piston uppers have NO gas traveling into the bolt to act on the gas rings, yet they still work.
Link Posted: 2/27/2006 9:55:16 AM EDT

Originally Posted By Tempest45:
The fact that gas piston uppers work is proof that the gas rings do not need to be aligned. Piston uppers have NO gas traveling into the bolt to act on the gas rings, yet they still work.



I think you are misunderstanding how the AR15 works, and the role of the gas rings (if any) in a piston operated upper.

In a conventional AR15 the gas bled from the barrel feeds back through the gas tube, into the carrier behind the gas rings. There is nowhere for the gas to go, so pressure builds up, pushing on the gas rings (and hence the bolt) in one direction, keeping the bolt closed, and on the bolt carrier in the opposite direction, forcing it backwards. As the bolt carrier moves back it turns the bolt, unlocking it and eventually the bigger mass of the bolt carrier moving backwards, pulls the bolt open.

So in the conventional AR15 the gas rings do need to form some sort of gas seal -- but actually not a complete seal, just an impediment to gass flow, since there is a lot of gas under high pressure and a bit of a leak is not important.

With a piston upper the mechanism is completely different. Gas bleeds from the barrel and the gas tube takes it to a cylinder containing a piston - the gas pushes the piston back and a mechanical arrangement (push-rod) pushes the bolt carrier backwards. In this case, the gas rings are not performing any gas function -- basically, all they are doing is acting as a spacer/bearing for the rear end of the bolt.
Link Posted: 2/27/2006 9:56:27 AM EDT
What gas rings do in the privacy of their own carrier is none of my business!
Link Posted: 2/27/2006 11:53:23 AM EDT
Remove all doubt and go to the MacFarland one piece gas rings. Never a gap!

Tack
Link Posted: 2/27/2006 11:58:28 AM EDT
[Last Edit: 2/27/2006 12:19:53 PM EDT by Tempest45]

Originally Posted By PhilipPeake:
I think you are misunderstanding how the AR15 works, and the role of the gas rings (if any) in a piston operated upper.

In a conventional AR15 the gas bled from the barrel feeds back through the gas tube, into the carrier behind the gas rings. There is nowhere for the gas to go, so pressure builds up, pushing on the gas rings (and hence the bolt) in one direction, keeping the bolt closed, and on the bolt carrier in the opposite direction, forcing it backwards. As the bolt carrier moves back it turns the bolt, unlocking it and eventually the bigger mass of the bolt carrier moving backwards, pulls the bolt open.

So in the conventional AR15 the gas rings do need to form some sort of gas seal -- but actually not a complete seal, just an impediment to gas flow, since there is a lot of gas under high pressure and a bit of a leak is not important.

With a piston upper the mechanism is completely different. Gas bleeds from the barrel and the gas tube takes it to a cylinder containing a piston - the gas pushes the piston back and a mechanical arrangement (push-rod) pushes the bolt carrier backwards. In this case, the gas rings are not performing any gas function -- basically, all they are doing is acting as a spacer/bearing for the rear end of the bolt.



I am aware of how the AR15 gas system works. (Very good description though) The one thing that I would add is that as the Carrier continues moving back, holes in the side of the Carrier move past the gas rings and pressurized gas is allowed to escape out the ejection port.

I didn't say that gas rings were not needed, just that misalignment is not necessary. I suspect that the main function of the gas rings is to maximize the containment of debris inside the expansion chamber. This is where the above addition come into play. The gas has to go somewhere. The rings simply contain the gas until the pressure has dropped enough to expel outside.

ETA: The gas does push on the back of the bolt. This is part of an "equal but opposite" reaction similar to hydraulics. The bolt is locked in place at this time by the barrel extension so the gas cannot move it. The carrier is held only by a spring so it is free to move away (opposite) from the bolt. The bolt becomes, in effect, a fixed piston with the "cylinder" moving around it.

If the rings were not there, the main bearing surfaces of the bolt/ejector/extractor would all be exposed to greater fouling than they are now. I think this can be seen in the fact that gas rings are so cheap. If a tight gas seal was needed, gas rings would need much tighter tolerances, and they simply wouldn't be thin, cheap, stamped sheet metal parts. The gas rings on my AR float around on the bolt, and are not tight in any direction of movement, yet it has never failed to function.

IMHO, the reason for having 3 is redundancy, survivability and cost (see above). Redundancy is obvious, there are 3. If one fails, there are 2 more still working. Serviceability: small, thin parts are easier to replace in the field than is a single, large, thick part.

I also have a FAL so I am very familiar with gas piston actions as well. The fact that a piston powered carrier will cam/open the bolt and cycle the weapon shows that there is no need for gas pressure to act upon the rings in order for the weapon to function. This is perhaps what I should have stated in my first post.
Link Posted: 2/28/2006 10:18:21 AM EDT
Ok - now I see what you were saying.

Sorry if I seemed to treat you as if you knew nothing -- but a lot of the time people do (know nothing) and are looking for information, and typically get a "you are a moron" response and nothing helpful -- so when I have the time, I try to give a full repsonse.

Yes - I should have mentioned the gas exhaust holes.

I don't know about the rings just being there for containment -- remember the gas pulse is fast, so there is little time for gas to leak around the rings, they are more of an impediment than a real gas seal, just enough to allow the pressure to build enough to give enough momentum to the bolt carrier to do its thing.

As you mention, it would be possible to make this work without the gas rings, just using the bolt to provide the required "impediment" for the gas. However, the volume of the resulting chamber would be significantly higer, so more gas would be required, and it would take longer to get the required pressures. This would mean a larger bleed hole on the barrel, larger gas tube, and probably significantly more crap dumped inside the rifle.

The AR15 design is deceptively simple to look at. I suspect it took a lot of engineering and experimentation to get things to a reasonable compromise and reasonable reliability.
Link Posted: 2/28/2006 11:42:50 AM EDT

Sorry if I seemed to treat you as if you knew nothing -- but a lot of the time people do (know nothing) and are looking for information, and typically get a "you are a moron" response and nothing helpful -- so when I have the time, I try to give a full repsonse


It's all good. Like I said, the description you gave was very good. And up until a few months ago, I didn't know how it worked. That changed after extensive reading on this site.


I don't know about the rings just being there for containment -- remember the gas pulse is fast, so there is little time for gas to leak around the rings, they are more of an impediment than a real gas seal, just enough to allow the pressure to build enough to give enough momentum to the bolt carrier to do its thing.

As you mention, it would be possible to make this work without the gas rings, just using the bolt to provide the required "impediment" for the gas. However, the volume of the resulting chamber would be significantly higer, so more gas would be required, and it would take longer to get the required pressures. This would mean a larger bleed hole on the barrel, larger gas tube, and probably significantly more crap dumped inside the rifle.



The more I think about it, I think you are right. I like the word "impediment", because the rings sure aren't what I would call seals. But they (the rings) are needed to form extra surface area for the gas to push against.


The AR15 design is deceptively simple to look at. I suspect it took a lot of engineering and experimentation to get things to a reasonable compromise and reasonable reliability.


I fully agree with this, and Vietnam + Troubleshooting forum demonstrate it.
Link Posted: 3/1/2006 6:31:07 AM EDT
There needs to be a gap, that way when you push the bolt into bc, the rings can collapse.
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