View Full Version : Gas Rings
This is as good a place as any I suppose for this. This has to do with maintenance and life expectancy of parts. Today I issued out 5 BM carbines (semi-auto) so we could qualify and vet a few local nationals. The carbines in questions haven't see much hard use at all. They have been here longer than me, so I have no idea what the actual round count is.
All the weapons were clean and before I handed them out I did the basic check as well as checking the BCG and gas rings. Two of the five failed the gas ring check. These weapons were also used just a few weeks ago and I can only assume that they either didn't shoot them or they malfunctioned and it was chalked up to "normal". I replaced the rings and sent them on their way. Here is the odd part. After they fired them the weapons were brought back and I was told that 2 of them were malfunctioning (classical short stroking going on). I am totally scratching my head because I had just checked them. Sure enough I cleaned them again, check the gas rings and both failed. We are talking about less than 60 rounds being fired from the time they went out till when they came back.
So back to cleaning and maintenance. I think that this shows why it is smart to clean your stuff after shooting. At a minimum the BCG because there just is no way to tell when something is going to break or wear out. This could have been a fluke for sure, but I am keeping my eye closer on ths situation.
Sidewinder6
06-09-09, 10:39
One test I learned about was to stand the bolt on its face with the carrier (clean) on a flat surface like a table and if the carrier slides down at all , the rings require replacement.
There are many pros here who may have another way to do this.
Sidewinder,
That is the test that I do (and did) as well. ;)
One test I learned about was to stand the bolt on its face with the carrier (clean) on a flat surface like a table and if the carrier slides down at all , the rings require replacement.
There are many pros here who may have another way to do this.
I honestly did not know the proper method of checking my gas rings. Thanks for sharing :)
The other thing about gas rings is that they are NOT all created equal. On the cheaper brands, we typically find gas rings that need to be changed out after a few hundred rounds!
C4
Had a batch of PM-spares from a certain bottomfeeder that included gas rings. I did a batch of guns, and they all failed the test within a couple of qualifications.
My gas ring test: I hold the BCG by the upright bolt. If the BC drops free from bolt, or nearly does, the rings get replaced. This method produces earlier failure than some others but there's nothing wrong with higher standards.
Rings are cheap, even the good ones.
Jay Cunningham
06-09-09, 11:27
This may also indicate poor machining of the inside of the carrier.
After I got here we started the switch to McFarlands and I can honestly say that we have had ZERO problems with them.
The other thing about gas rings is that they are NOT all created equal. On the cheaper brands, we typically find gas rings that need to be changed out after a few hundred rounds!
C4
I wondered about this as well, though the inside seems to be fine.
This may also indicate poor machining of the inside of the carrier.
Speaking theoretically, could a poorly machined bolt carrier be rougher on gas rings due to surface imperfections or tool marks on the interior surface of the carrier itself? This would (I would think) wear out gas rings more quickly than a carefully machined carrier, no matter the quality of the rings themselves.
I always check gas rings and usually using both the place the extended bolt and carrier(no guts) on the bolt and look for collapse and then I collapse the assembly and hold the bolt and see if the carrier slides under its own weight. I can only assume there are alot of variables in ring quality (not just manufacture, but by also batch) and carrier dimensons because I have relpaced rings at all sorts of intervals, but so far not less than 2k. I think it is a good idea to have several sets of rings around because they can go at any time.
Failure2Stop
06-09-09, 11:44
Gas rings are funny.
I have had M4A1s that wouldn't come close to passing the gas-ring test, but would chew through a grand of M855 over a week long course.
Seems to me that if all else in the system is working in harmony, the gas rings are much less of a concern.
I have also shot M4s with one and even two gas rings removed (standard CAR buffer and used but within limit action spring). Once again, if lubed and all else is right and fed good ammo (M855), no problem for at least 30 rounds.
This is not to say that gas rings are not important, just quirks of the system I guess.
One test I learned about was to stand the bolt on its face with the carrier (clean) on a flat surface like a table and if the carrier slides down at all , the rings require replacement.
There are many pros here who may have another way to do this.
Cool! Thanks for posting that. Was just thinking about asking how to test them after reading Gunz' post. :D
QuietShootr
06-09-09, 20:25
The other thing about gas rings is that they are NOT all created equal. On the cheaper brands, we typically find gas rings that need to be changed out after a few hundred rounds!
C4
Do you stock the good gas rings?
Do you stock the good gas rings?
Yes he does.
http://www.gandrtactical.com/cgi-bin/commerce.cgi?preadd=action&key=GR-AR15&reference=/cgi-bin/commerce.cgi%3Fsearch%3Daction%26keywords%3Dgas%20rings%26searchstart%3D0%26template%3DPDGCommTemplates/FullNav/SearchResult.html
If the bore of the carrier is machined rough the hard chrome will act like a file. The plating is actually quite a bit harder than the average file. Electro plated hard chrome plating builds rough spikes on any sharp edges like machining marks.
Things like hydraulic cylinders that are hard chrome plated are honed after plating to avoid chewing up the seals.
So....what would the procedure for replacing the gas rings be? As always a qualified gunsmith would be the best bet, but is it something that's a pain to do? Or simple stupid that can be done by a serious shooter wanting to maintain his weapon? I put at any given month 100 rds through my AR. 2k since I've had her, Thanks for the great info. Very interesting.
Heavy Metal
06-09-09, 21:32
I have found if you heavily lube the interior of the BCG and keep it lubed, the gas rings last phenomenally longer. I got 9K out of a set and they still passed when I replaced them.
Blankwaffe
06-10-09, 01:20
The other thing about gas rings is that they are NOT all created equal. On the cheaper brands, we typically find gas rings that need to be changed out after a few hundred rounds!
C4
BINGO!
Ive been complaining about this for months due to the exact same experience and is why I PM'd you about quality gas rings sometime back.
Some of the gas rings Ive got from a few of the manufacturers dont have the usual tear drop ends either,but rather a slash like cutout on the ends.Service life is extremely short on these by the way.Im talking a matter of a few mags.
I took your advice and installed the McFarland rings.No problems since.
gog,
Anyone with a little mechanical ability can replace gas rings.
1. Remove old gas rings. You can use needle nose pliers or a dentist pick to lift the ring and then force it out of the groove. Once you have removed all three clean up any debris in the channel.
2. Take your new McFarland ring and with a finger start one side of the coil into the channel. Once there hold it in place and then use another finger nail to feed the rest of the gas ring and it will essentially "peel" into place. That's it. It takes about 45 seconds or so. YMMV.
So....what would the procedure for replacing the gas rings be? As always a qualified gunsmith would be the best bet, but is it something that's a pain to do? Or simple stupid that can be done by a serious shooter wanting to maintain his weapon? I put at any given month 100 rds through my AR. 2k since I've had her, Thanks for the great info. Very interesting.
tango-papa
06-10-09, 15:45
gog,
Anyone with a little mechanical ability can replace gas rings.
1. Remove old gas rings. You can use needle nose pliers or a dentist pick to lift the ring and then force it out of the groove. Once you have removed all three clean up any debris in the channel.
2. Take your new McFarland ring and with a finger start one side of the coil into the channel. Once there hold it in place and then use another finger nail to feed the rest of the gas ring and it will essentially "peel" into place. That's it. It takes about 45 seconds or so. YMMV.
So essentially, just like a key ring, eh?
Never seen the McFarland rings in person, which is going to change soon, after reading this thread.
~tp
Roger that.
So essentially, just like a key ring, eh?
Never seen the McFarland rings in person, which is going to change soon, after reading this thread.
~tp
Failure2Stop
06-10-09, 17:20
Gunz-
What kind of average life are you seeing from the McFarlands?
If you haven't killed any of them yet do you have a "not less than" roundcount?
Funny you should ask. I have an upper that I put together here several months back when I was testing the Prvi Partizan and Bulgy SS109 ammo. The bolt and everything was rebuilt using new McFarlands. I put just over 1400 rounds through the upper in a span of 4 sessions mostly on auto. It still feels tight and I hope to launch some more rounds again soon.
Gunz-
What kind of average life are you seeing from the McFarlands?
If you haven't killed any of them yet do you have a "not less than" roundcount?
Blankwaffe
06-10-09, 20:23
IG and F2S,
Ive got one McFaralnd ring that Ive got a little over 2,200 rounds on in the last 10 months and it still feels and looks good to go.Not as tight of a fit as it was new,but good to go.All SA use in a Defender 2000 16".I try to keep the rings lubed well with WS-CLP periodically while in use too.I'd be willing to say the rings would be good to 4,000 judging by the way mine is holding.
gog,
Anyone with a little mechanical ability can replace gas rings.
1. Remove old gas rings. You can use needle nose pliers or a dentist pick to lift the ring and then force it out of the groove. Once you have removed all three clean up any debris in the channel.
2. Take your new McFarland ring and with a finger start one side of the coil into the channel. Once there hold it in place and then use another finger nail to feed the rest of the gas ring and it will essentially "peel" into place. That's it. It takes about 45 seconds or so. YMMV.
Ok. Thanks. What I really was looking for was the trick to the trade b4 I destroy a set of rings in the process of figuring it out. Thanks for the input. I'm sure it helped a couple of us out.
Thanks
IraqGunz: possiblity of a leaking gas key?? I have seen them where they're still on and don't wiggle, but leak and cause the weapon to short stroke. Just askin....:D
Ofc.JL
Not as far as I can tell. The rings just took a crap at the last minute.
IraqGunz: possiblity of a leaking gas key?? I have seen them where they're still on and don't wiggle, but leak and cause the weapon to short stroke. Just askin....:D
Ofc.JL
PRGGodfather
06-11-09, 16:28
After I got here we started the switch to McFarlands and I can honestly say that we have had ZERO problems with them.
I am of similar mind.
The McFarland's one-piece, multiple coil spring-like design makes it difficult to compress, so they seem tight even after 3,000 rounds.
The McFarlands run about 40 cents more than entire set of 3 individual rings at Brownells -- and simply, I expect they will continue to work for at least another 3,000 rounds.
THAT is 40 cents well spent, IMHO...
RogerinTPA
06-11-09, 17:28
Hey Guns, any tips on the installation of gas rings without damaging them? I have a couple that I wanna change out since the BCGs have close to 5K rounds on, for PMCS. What's your change out schedule?
rharris,
Which type? There is no real tip to doing it per se. Just start one end into the groove and feed them in. The same with the McFarlands. Since I clean my weapons regularly and inspect them at the same interval using the aforementioned technique I replace them when they fail. I don't believe that there is an established round count yet.
Hey Guns, any tips on the installation of gas rings without damaging them? I have a couple that I wanna change out since the BCGs have close to 5K rounds on, for PMCS. What's your change out schedule?
RogerinTPA
06-11-09, 18:50
rharris,
Which type? There is no real tip to doing it per se. Just start one end into the groove and feed them in. The same with the McFarlands. Since I clean my weapons regularly and inspect them at the same interval using the aforementioned technique I replace them when they fail. I don't believe that there is an established round count yet.
They are two Colt bolts. The rebuild kits are BCM.
I've read some folks replace springs, rings and extractors at 5K intervals for reliability. I had an extractor fail at the 5K mark and replaced it. I figured you'd have a self established PMCS schedule for your weapons since they are getting higher than average round counts in a shorter period of time.
So, just replace the rings when they fail?
Awesome thread. Gas rings had always been a bit of a mystery to me. When playing with my BCM BCG it takes much more effort to push the bolt back into the carrier than it does on "the other guy's BCG". I suppose this is a sign of high quality rings?
rharris,
The problem is that no one here keeps track of how many rounds have been fired in their weapons. Also, because we are a business the corporate warfighting machine has a different view about replacing stuff before it breaks or wears out.
This is why I preach to the flock that they should regularly clean (and at a minimum) inspect their weapons. By following the guidelines and knowing how your weapons shoots you will know when problems develop. Unfortunately there is no science in determining when a spring goes bad, an extractor will break or anything else.
They are two Colt bolts. The rebuild kits are BCM.
I've read some folks replace springs, rings and extractors at 5K intervals for reliability. I had an extractor fail at the 5K mark and replaced it. I figured you'd have a self established PMCS schedule for your weapons since they are getting higher than average round counts in a shorter period of time.
So, just replace the rings when they fail?
I used to swear by the McFarland Gas rings. The last two batches I bought were made by Fulton Armory and DPMS. The outside demension varied so much that one bolt wouldn't even go into the carrier.
I guess McFarland let these other guys make them and the specs arn't what they used to be.
For BCG parts and even Complete BCG's I go with Bravo Company.
I'm not a fan of the McFarland rings, but am not wholly a pundit either.
I've seen them stop working guns. They've also corrected quirky issues in others that weren't working, not unlike ring wear discussed here.
Prefer OEM, but the McFarland may be useful for some.
Rock-N-Ruin
07-02-09, 12:25
I just installed a set last night for the first time and they seemed quite hard to get the bolt inside the carrier, I figured that was normal and they will seat and hopefully work fine.. They sure are tight and I hope they don't cause any problems as mentioned in the last couple posts.. We'll see what happens.. Rock.
I have outfitted at least 150 of our auto carbines with them and not one has ever had a problem. Remember that your carbine or rifle generates anywhere from 35-55K PSI in the chamber and as long as all of your other parts are working as they should then you are GTG. As usual make sure that you lube correctly.
I just installed a set last night for the first time and they seemed quite hard to get the bolt inside the carrier, I figured that was normal and they will seat and hopefully work fine.. They sure are tight and I hope they don't cause any problems as mentioned in the last couple posts.. We'll see what happens.. Rock.
BushmasterFanBoy
07-02-09, 23:53
This is quite curious to me, as I can't recall the last time either of my carbine's BCG's passed the "gas ring test" when properly cleaned and lubed. (or if they ever did to begin with)
That said, I haven't had trouble out of them at all, but what signs would one look for in a gas-ring related malfunction? What makes them "worn out"? I've never payed much attention to the gas rings, as they seem to be a mystery to me. Can we get something like a "gas rings for dummies" in here? :confused:
ETA: If my guns are working fine, but failing the gas ring test, should I still replace them, or is this a case of "if it ain't broke, don't fix it"?
This is quite curious to me, as I can't recall the last time either of my carbine's BCG's passed the "gas ring test" when properly cleaned and lubed. (or if they ever did to begin with)
That said, I haven't had trouble out of them at all, but what signs would one look for in a gas-ring related malfunction? What makes them "worn out"? I've never payed much attention to the gas rings, as they seem to be a mystery to me. Can we get something like a "gas rings for dummies" in here? :confused:
ETA: If my guns are working fine, but failing the gas ring test, should I still replace them, or is this a case of "if it ain't broke, don't fix it"?
if the weight of the carrier is enough to make 'em sink or suck, replace.. it's preemptive, yes- but cheap and easy... so why not?
BMFB,
Think of the rings bolt rings like the rings in an engine. They provide a seal so to speak. Once they wear out you will have problems. Gas ring related malfunctions generally manifest themselves as short-stroking issues. Replacing them BEFORE they wear it is PREVENTATIVE maintenance. I have also seen some carbines that failed the test that worked also. The question is for how long? When diagnosing such issues the common sense approach is to inspect for the obvious, loose carrier key, loose gas tube (because roll pin is missing), etc... Once that is done then you move on to replacing parts. Generally this means replacing the cheapest part in the chain first (gas rings) tube, etc.. Of course this assumes that you have the right configuration of parts and that the platform actually ran right to begin with.
One issue that I saw at place where I worked before was gas port erosion. This had to do with the high round counts that were being pout through the weapons. After a point the only fix for that is a new barrel.
This is quite curious to me, as I can't recall the last time either of my carbine's BCG's passed the "gas ring test" when properly cleaned and lubed. (or if they ever did to begin with)
That said, I haven't had trouble out of them at all, but what signs would one look for in a gas-ring related malfunction? What makes them "worn out"? I've never payed much attention to the gas rings, as they seem to be a mystery to me. Can we get something like a "gas rings for dummies" in here? :confused:
ETA: If my guns are working fine, but failing the gas ring test, should I still replace them, or is this a case of "if it ain't broke, don't fix it"?
Ned Christiansen
07-05-09, 19:14
There is a little joke amongst our training cadre-- to remove bad gas rings, use Tide.
Gunz, I have always recommended against the McFarlane gas rings but to be honest you are the first and best source of "actual" info and numbers I've ever had. If you say they're good it means I need to revisit this.
Ned,
What are some of the issues that have been encountered with them? When I slapped that Colt/BM upper together back in November I acquired a Colt bolt and put new McFarlands on it. I then put just over 1400 rounds through it in a course of 4 days. No issues other than the quirky ammo stuff.
BTW- keep your out for another order. I'll be getting another complete reamer plus a refill. :D
There is a little joke amongst our training cadre-- to remove bad gas rings, use Tide.
Gunz, I have always recommended against the McFarlane gas rings but to be honest you are the first and best source of "actual" info and numbers I've ever had. If you say they're good it means I need to revisit this.
Ned Christiansen
07-06-09, 11:13
Well Gunz, it's one of those deals where a few of us had bad first experiences with them, plus a bit of lore, I'm sure now long untraceable, that one of the mfgrs said the McFarlanes were for match only and not street use-- from this we created the dogma of, don't use them at all for anything.
I am always game to re-examine my position on things-- I will re-check this as I get the chance.
geminidglocker
07-06-09, 11:18
I watched an instructor remove the gas rings completely and proceed to fire 30 rounds with out an issue. So i'm running the Mcfarland 1 peice gas ring and it's wicked loose but has not faile in 3500 rounds with minimal cleaning.
Think of the rings bolt rings like the rings in an engine. They provide a seal so to speak.
Please excuse my ignorance, but could you please explain this?
I think I understand how piston rings work in an IC engine, and I think I understand how the AR-15's gas system works, but I don't understand what the "gas rings" in the M16/AR are sealing anything.
IIRC, IC piston rings aren't all the same. There are "compression rings," which seal, and "oil rings," which scrape the oil off the walls of the cylinder so it doesn't wind up in the combustion chamber.
IIRC, the DI gas system runs gas through the tube into the gas key, which is a snug enough fit to "seal." Then, when the bolt carrier moves rearwards far enough, the gas tube isn't in the gas key anymore, then there's no more gas driving the bolt carrier rearward.
It's the bolt carrier moving rearward which cams the bolt counter-clockwise to unlock it from the barrel extension and then pulls it to the rear.
The point is, unless I totally misunderstand the DI system, there's no gas driving anything anywhere near the "gas" rings.
My guess (without having mine here to study) is that the rings are to center the bolt in the bolt carrier, and to reduce the friction of the bolt turning within the bolt carrier.
Maybe they're like "oil rings," and they keep the oil/lube away from the front of the bolt and the chamber, too.
So, I can understand why newer/better rings would make the rifle function better, but it's not because they're "sealing," anything.
It's because they're centering the bolt in the bolt carrier and reducing the friction between the two moving parts better.
Or do I totally misunderstand this?
Again, I'm pretty new to the M16/AR, so please forgive my ignorance,
Bimmer
gas rings do seal gas- they keep the pressure inside the carrier section of the assembly, allowing it to proceed rearward while the bolt stays locked until the carrier has progressed far enough to actuate the cam-pin, unlocking the bolt at the correct time. without gas rings, keeping the bolt in place and pressing the carrier back, the carrier might not have enough pressure to overpower the chamber pressure against the bolt's locking lugs... leaving you with a single-shot rifle.
obviously guns HAVE functioned with worn and/or missing rings, but not reliably.
Bimmer,
What he said. Maybe I didn't explain it 100% correctly. So in your spare time try this. Take your gas rings and remove them from the bolt. Then reassemble your weapon and go out to the range and see what happens.
Another thought to ponder. If your gas rings are worn you will at some point start experiencing malfunctions. Once you replace them you will be back in the game. So how would you describe or explain that? Also, if you remove the gas rings the rear tail of the bolt will make almost no contact within the bolt carrier.
gas rings do seal gas- they keep the pressure inside the carrier section of the assembly, allowing it to proceed rearward while the bolt stays locked until the carrier has progressed far enough to actuate the cam-pin, unlocking the bolt at the correct time. without gas rings, keeping the bolt in place and pressing the carrier back, the carrier might not have enough pressure to overpower the chamber pressure against the bolt's locking lugs... leaving you with a single-shot rifle.
obviously guns HAVE functioned with worn and/or missing rings, but not reliably.
superman07
07-06-09, 21:04
Had a RRA from the factory with the loosest rings I had ever experienced. But that rifle was so over gassed it ran ok.
No worries, I don't doubt WHETHER rings are necessary, I just doubt WHY they're necessary.
I'm still thinking about this, and this still doesn't make sense to me. I have a hard time thinking that the gas system pressurizes the entire carrier — this seems impossible.
I also can't imagine that the operating system needs more gas than the initial jolt that gets the carrier key off the gas tube. AFAIK, inertia then keeps the carrier (and the buffer, and ultimately the bolt and the hammer) moving rearwards.
When I get home I'll pull my rifle apart and look at it closely and maybe this'll make sense...
Bimmer
The gas rings in a DI gun act as the piston (FYI).
C4
The gas rings in a DI gun act as the piston (FYI).
C4
OK, now I'm starting to feel stupid, because I still don't get it...
I thought that the whole bolt carrier functions as a piston — it's the carrier that's driven (via the gas key) by the gas coming through the gas tube.
The important "seal," then, is between the gas tube and the gas key. Once they disengage, then nothing's being "driven" by gas pressure and it's just inertia which keeps everything moving rearward. Is this wrong?
Again, I'm sure that the bolt rings serve a function, but I still don't see how they're "sealing" anything.
I'm sorry if I'm being thick-headed...
Bimmer
Thomas M-4
07-08-09, 09:10
No worries, I don't doubt WHETHER rings are necessary, I just doubt WHY they're necessary.
I'm still thinking about this, and this still doesn't make sense to me. I have a hard time thinking that the gas system pressurizes the entire carrier — this seems impossible.
I also can't imagine that the operating system needs more gas than the initial jolt that gets the carrier key off the gas tube. AFAIK, inertia then keeps the carrier (and the buffer, and ultimately the bolt and the hammer) moving rearwards.
When I get home I'll pull my rifle apart and look at it closely and maybe this'll make sense...
Bimmer
Bimmer it sounds like to me you kinda answered your on question . The gas rings seal it up enough so that there is a good jolt to the carrier.[sorry about the lack of good terminology] to unlock the bolt and to
begin extraction then inertia takes the carrier the rest of the way
OK, now I'm starting to feel stupid, because I still don't get it...
I thought that the whole bolt carrier functions as a piston — it's the carrier that's driven (via the gas key) by the gas coming through the gas tube.
The important "seal," then, is between the gas tube and the gas key. Once they disengage, then nothing's being "driven" by gas pressure and it's just inertia which keeps everything moving rearward. Is this wrong?
Again, I'm sure that the bolt rings serve a function, but I still don't see how they're "sealing" anything.
I'm sorry if I'm being thick-headed...
Bimmer
No on the bolt acting as a piston. Think about what a piston actually does.
C4
I have outfitted at least 150 of our auto carbines with them and not one has ever had a problem. Remember that your carbine or rifle generates anywhere from 35-55K PSI in the chamber and as long as all of your other parts are working as they should then you are GTG. As usual make sure that you lube correctly.
edit: sorry, dumb question...
OK, now I'm starting to feel stupid, because I still don't get it...
I thought that the whole bolt carrier functions as a piston — it's the carrier that's driven (via the gas key) by the gas coming through the gas tube.
The important "seal," then, is between the gas tube and the gas key. Once they disengage, then nothing's being "driven" by gas pressure and it's just inertia which keeps everything moving rearward. Is this wrong?
Again, I'm sure that the bolt rings serve a function, but I still don't see how they're "sealing" anything.
I'm sorry if I'm being thick-headed...
Bimmer
not thick headed, think of it this way - the bolt is the piston inside the cylinder (bolt carrier)
a round is fired and pressure is bled off the barrel and enters into a little chamber inside the BC behind the bolt through the gas key. the bolt is sealed inside this chamber inside the carrier by the rings.
since the bolt (piston) cannot move forward against the chamber, the pressure pushes the BC (cylinder) rearward against pressure of the buffer spring, which causes the bolt to rotate, unlocking it from the chamber.
the rearward inertia of the bolt carrier then allows it to pull the fully rotated bolt back out of the chamber.
the spring then pushes the bolt carrier group forward, picking up another cartridge from the magazine, and pushing the bolt forward into the chamber which is rotated into locked position by the continued forward movement of the BCG.
the bolt is locked into the chamber because its lugs are rotated behind the chamber locking lugs and the carrier is held forward by spring pressure until the next shot.
the AR system is cool in that it applies pressure to the back of the bolt equal to pressure on the face when it is time to unlock the bolt from the chamber. otherwise, it could not be unlocked.
did this help?
OK, now I'm starting to feel stupid, because I still don't get it...
I thought that the whole bolt carrier functions as a piston — it's the carrier that's driven (via the gas key) by the gas coming through the gas tube.
The important "seal," then, is between the gas tube and the gas key. Once they disengage, then nothing's being "driven" by gas pressure and it's just inertia which keeps everything moving rearward. Is this wrong?
Again, I'm sure that the bolt rings serve a function, but I still don't see how they're "sealing" anything.
I'm sorry if I'm being thick-headed...
BimmerBimmer, I don't know if the other, previous explanations have helped, but don't feel stupid. It simply sounds as though you don't understand how the Stoner AR10/AR15 series direct gas impingement system works.
It sounds to me that you believe that the gas from the gas tube impacts the gas key and that this impact drives the bolt carrier rearward. This is incorrect, as the gas key is simply a hollow tube, and not solid. The gas passes through the gas key and is injected into to bolt carrier.
Once inside the bolt carrier, the gas enters a chamber, where the only way for it to go is forward and push against the bolt and gas rings. This is why the gas rings are important. The gas within the bolt carrier effectively causes the bolt and bolt carrier to try and seperate.
At this point, the bolt is locked into the barrel and can't move forward, so the bolt carrier moves rearward. This rearward movement of the bolt carrier is due to the gas pressure within the chamber. As the bolt carrier moves rearward, the bolt rotates and unlocks from the barrel extension due the the movement of the cam pin within the bolt carrier keyway. As the bolt is turning to unlock, the bolt's gas rings move past the gas port holes in the right side bolt carrier, and the gas is then vented outside the rifle.
Ironically, your concept of the direct gas impingement system more closely represents the gas path of the Swedish AG42 Llungman, which was the first major rifle design to use a direct gas system. In the Llungman, the gas impacted directly upon the bolt carrier, and was not vented within the carrier, as with the the Stoner system. That's why you shouldn't feel stupid.
It sounds to me that you believe that the gas from the gas tube impacts the gas key and that this impact drives the bolt carrier rearward. This is incorrect, as the gas key is simply a hollow tube, and not solid. The gas passes through the gas key and is injected into to bolt carrier.
Once inside the bolt carrier, the gas enters a chamber, where the only way for it to go is forward and push against the bolt and gas rings. This is why the gas rings are important. The gas within the bolt carrier effectively causes the bolt and bolt carrier to try and seperate.
Ironically, your concept of the direct gas impingement system more closely represents the gas path of the Swedish AG42 Llungman, which was the first major rifle design to use a direct gas system. In the Llungman, the gas impacted directly upon the bolt carrier, and was not vented within the carrier, as with the the Soner system. That's why you shouldn't feel stupid.
Thanks, Beckman, THIS does make sense to me, and I don't feel like a knucklehead anymore!
When I get home and get my hands on my AR, then I'm sure it'll be even more clear to me.
Learning, learning, learning,
Bimmer
Wir haben einen Gewinner! :D
Thanks, Beckman, THIS does make sense to me, and I don't feel like a knucklehead anymore!
[...]I'm glad to hear that I helped.
faawrenchbndr
07-09-09, 18:59
Tons of great info in this thread,...... thanks!
Powered by vBulletin® Version 4.2.5 Copyright © 2024 vBulletin Solutions, Inc. All rights reserved.