Gas rings and Bolt Carriers on AR-15

[Got_Lead?]

hello all:

I just got to wondering how often gas rings should be replaced on an AR-15. These seem like fairly stressed parts.

Also wondering if the bolt carrier should be replaced after a certain number of rounds, looking at the damage caused by a blow-out makes a person wonder if they should be changed out every so often.

Thanks

 

[roklok]

When the clean bolt carrier group with the bolt in the unlocked position resting bolt down on a flat surface will not stay "open" but closes under its own weight to the locked position. At least thats the way I was trained.

 

[MrCleanOK]

For when to replace gas rings, what roklok said. Extend the bolt from the carrier, stand the BCG up on the bolt face, and if the carrier stays up the gas rings are good. That said, your rifle will continue to run with as little as one beat up little gas ring. That doesn't mean it should, but it can.

As far as the carrier, I don't know the exact numerical answer, but the "good enough" answer is that you'll probably never fire enough rounds to warrant replacing a carrier. The bolt is a different story, but replacing the carrier will probably not be necessary as long as you own the rifle.

 

[BADUNAME37]

There is a spiral ring that you can install in place of the three rings with gaps. I installed them on several AR's with excellent results. After installing, I racked the bolt open and closed about 100 times to kind of seat them in.
http://www.brownells.com/.aspx/pid=18722/Product/AR_15_MCFARLAND_trade__BOLT_GAS_RING

McFarland Gas Rings

When I bought mine, I had only had my AR for several years and three times in a row, when I disassembled the BCG, I found the ring seperations lined up when I know I always configured them to be 1/3 away from each other around the circumference. So, I ordered like ten rings and replaced mine and a couple of others and still have spares. At the range, each time, the bolt wasn't extracting the empty casings properly, that is when I noticed the seperations pretty much lined up, as they should NOT be.

Being like a spring, they go on easily, one-coil at a time, wrapped around the bolt ring groove - kind of twisting it on, in place. A bit of Break-free, reassemble, and you could actually feel the difference when you moved the BCG slowly so the rings engage.

 

[madcratebuilder]

From the 23&P manual.

Check bolt assembly for proper fit with bolt
cam pin removed. Turn key and bolt carrier
assembly and suspend so the bolt assembly
is pointed down.

NOTE

The bolt assembly must not drop out. If
weight of bolt assembly allows It to drop
out of key and bolt carrier assembly,
replace bolt rings (p 3-21)

Standing the BCG on end well compress the bolt even with good rings.

With proper lube and maintenance the gas rings last a long time.

when I disassembled the BCG, I found the ring seperations lined up when I know I always configured them to be 1/3 away from each other around the circumference.

This is very common, it does not effect operation of the rifle. The rifle well operate even with one or two rings missing. I agree on the McFarland rings, I have had good luck with them. A lot of people have not had good results. Possible a fubar during install.

 

[BADUNAME37]

I only had less than 500 rounds on the OEM rings when I replaced them with these. I admit, I did not perform the drop-test, however, one would think that the original ring set should last longer than 500 rounds!

I have had the McFarland in now for at least three years with never a problem.

I know, for a fact that the three rings not properly aligned where causing sluggish BCG operation to the point, as I stated, where the empty casings were not properly ejecting, as, when I would then notice them and line them up in third quadrants, suddenly the BCG ejected emptys like a champ.

 

[gotigers]

IMHO

If the gun ejects properly, the rings are good. Obviously inspect them every cleaning. If you don't see any glaring damage, leave them be.

Same with bolt carrier. If it works leave it alone. With the caveat of inspection during cleaning.

If your worried about failure, keep spare parts with you; ejector, firing pin, hammer/trigger spring, bolt or bolt parts, etc.

 

[Tirod]

Frankly, the gas rings are redundant. It's been said more than once by those who did it the gun will function with just one working ring.

The spiral rings are nice, regular rings do the job in a much more cost effective way. They last thousands of rounds. Once the bolt is assembled and locked, the gap is extremely small, as the actual cylinder diameter tapers to compress them in the operating condition. They also rotate on the bolt in action, and no matter what you do, they will line up - but the gap is so small, high pressure remains trapped to cycle the action.

There are some who don't believe it, consider the fit of the gas key over the gas tube. It's NOT tight at all. Works just fine.

It's not rocket science, just simple automotives. Stoner worked it out 45 years ago. GI rings are all you need, and replacements are dirt cheap.

 

[Bartholomew Roberts]

I know, for a fact that the three rings not properly aligned where causing sluggish BCG operation to the point, as I stated, where the empty casings were not properly ejecting, as, when I would then notice them and line them up in third quadrants, suddenly the BCG ejected emptys like a champ.

If the tiny gap in the gas rings aligning makes the difference between your rifle functioning and not functioning, you've got a problem somewhere else.

 

[Tirod]

As I said, the rings rotate. The gaps WILL align. It means NOTHING, as the gap on the COMPRESSED ring assembly in the BCG is small enough that high pressure gas is trapped and the action cycles.

There's a gap at the gas key and tube, too.

There's a hole in the barrel that bleeds off gas, once the bullet passes it, does it stop? Make the gap small enough, and the effective result is that there is no gap.

If you're running a 6 cylinder motor to work, I can guarantee you the gaps on those rings line up, too. Does the engine completely miss a rotation when that happens? Does 3000 cc's of compressed exhaust suddenly vent into the crankcase? Hi speed photography show the rings rotating and gaps aligning, it's over in a split second, and the leakdown rate on a properly built new motor is less than 2%.

Gaps don't cause malfunctions, what is wrong is assuming they do when we all drive the counterargument to work every day.

Plenty of shooters AND soldiers have lined up the gaps deliberately and shot the AR with no affect whatsoever, some to their disgust. They were actually trying to induce a malfunction. It won't.

 

[Got_Lead?]

Thanks guys, the drop test makes sense for the rings. My AR is still pretty wet behind the ears, I've only fired a few hundred .223's fired out of it, it's probably not even broken in.

Sounds like I don't have anything to worry about.

I've noticed the same thing about the ring gaps, they do move around. I'll rotate them to the 12, 4, and 8 O'clock positions for assembly, and find them moved all around after firing a few rounds.

 

[possum]

I typical change things at the 5,000rd mark. If it is a gun that I bet my life on. If it is a training gun, I let it go until it needs attention. In my "fighting" carbine I place an order with BCM every 5 krds for a new bolt assmbly, and buffer spring. That is all that I change on a normal basis. keep it cleaned and well lubed (i use grease) and feed it good ammo(that works in your gun) and use quality mags and you will be good.

If have a good quality bolt carrier, IE and auto bolt from a reputable maker you will have to replace bolts, and gas rings, extractors and such way before you have to worry about the bolt carrier it self. I have been running ar's m-4's m-16's for many years both professionally as well as personally, attended many training courses, have seen a lot of things go wrong with ar's. Generally one of the things I listed above will be an issue (with the gun itself, not talking about ammo and magazines here) I have never seen a bolt carrier that needed to be replaced. A bolt being sheered? yes, broken or worn extractors? yes. short strokes because of bad rings? yes.

When the clean bolt carrier group with the bolt in the unlocked position resting bolt down on a flat surface will not stay "open" but closes under its own weight to the locked position. At least thats the way I was trained.

I was trained in this manner as well in the Infantry, however with my personal guns I have tested this theory and I do not see that this has merit to it.

 

[Onmilo]

I use McFarland gas rings in some of my rifles and standard gas rings in others.
The acid test is whether the McFarland rings affect reliability in a particualr weapon.
Some rifles function fine with them and some hang up and jam with the McFarland ring installed.
Only way to know for sure is to test your rifle with one installed.

If your rifle DOES work reliably with the McFarland in place you will not need to replace the gas ring assembly again as it will likely outlast the bolt.

As for bolt carriers.
I repaired M16 rifles while i was in service in the Army.
Bolt carriers were almost never replaced, the main reason for replacement would be the gas key bolts shearing off with the gas key missing or hanging on by a thread.
Sometimes we would get a rifle with the cam port all buggered up but that was very rare.
Other rifles came in for rebuild/repair that had early chromed carriers and these were replaced with dark parkarized carriers because overseas and combat servicability requirements would not allow for chromed carriers installed on rifles intended for combat use.
As long as the gas key is sound and tight, the cam port isn't wallowed, the firing pin retainer pin through hole isn't misdrilled and the bolt doesn't fall out of its own weight, a carrier is good to go.
Bolt carriers, buffers, and recoil springs last a very, very, long time in M16 type rifles.

 

[possum]

correction to my above post. I have seen carriers that were not properly staked have issues in classes, and one sheer off, however the rate of this happening, especially among quality built guns is much less occurring that the other issues that I listed.

 

[TonyAngel]

I wouldn't bother with the McFarland ring. I've had them and they don't do anything that the stock type of rings won't. In some bolt/carrier combinations, the McFarland will induce a failure to cycle properly.

Rings are pretty cheap and you should have a few spare sets regardless. I've seen oem rings go bad in as litle as 300 rounds. Get quality rings and keep a spare set or two with the rifle. I usually order my rings and extractor springs from Bravo Company and they last a good while.

 

[feedthehogs]

The evil of good is better.

 

[mc223]

I must add to the NO vote on McFarland ring.

May have some specialized application where a McFarland ring would excel. I just cant think of any offhand.

 

[Kwanger]

I have a couple of the McFarlands, and they work in the rifles they are in....but on the other hand they don't do anything the standard rings don't, and there just seems to be too much noise to me that you may encounter issues with them. Doubt I'll buy any more...you can get a lifetimes supply of the standard rings for $5, think I'll stick with those in future.

Bolt carriers...as others have said, very slim chance of those failing.

 

[dogrunner]

I tried the spiral one piece ring assy Brownell's offers on my mid-length..............certainly it worked, but the device gave far, far less obturation than the standard ring set......In fact you could hold the carrier upright and the bolt would retract with a mere shake.

Seemed like a good idea on first examination and perhaps I got a defective assembly, regardless my old ones work well and are now back on the bolt.

 

[W.E.G.]

I have "heard" that an AR-15 that does not otherwise have cycling problems will usually work with just one ring.

Not recommending it.
But something to think about it whey you are experiencing compression anxiety.

I think gas rings get spuriously blamed for every sort of jacked-up AR malfunction.

 

[dirtykid]

I have tried both the Mcfarlands and the standard 3-pc rings, and come to the conclusion that the standard rings work just as well,last just as long and are alot cheaper!

 

[Jeremy2171]

If the tiny gap in the gas rings aligning makes the difference between your rifle functioning and not functioning, you've got a problem somewhere else.

What he said!