Tech Tip: How To Replace an AR-15 Gas Key

The AR-15 platform is extremely robust, but as with any mechanical device, parts sometimes break and you have to replace them. Brownells Gun Tech™ Caleb Savant shows us how to replace the gas key on the AR-15's bolt-carrier group (BCG). The gas key sits atop the carrier and is the conduit that directs gas from the gas tube through the bolt-carrier group to cycle the action. If the gas key is loose, you get a gas leak that can cause cycling problems and malfunctions. TECH TIP: If you're having cycling problems, before you replace or realign the gas block, check for a loose gas key first.
REMOVAL: The first step is to remove the old gas key from the carrier. Grab a driver with the correct-size bit to fit the gas key screws and loosen them. The screws should be staked, so it may take some effort to overcome the staking. If the gas key has been leaking, you'll see a lot of carbon crud under it and around the gas port in the top of the carrier. Cheaply made BCGs often have poor contact surfaces between the carrier and key and are prone to gas leakage. A high-quality bolt-carrier group is much better machined, fits better, and will last longer. You get what you pay for.
Get some steel wool and clean up the top of the carrier where the gas key sits. Degrease it with a good gun cleaner, such as Birchwood-Casey Gun Scrubber. Clean any debris or old thread-locker out of the screw holes.
KEYED UP: When you replace the gas key, ALWAYS replace the gas key screws, too. Make sure you get good-quality, Grade A screws. A lot of force comes to bear on the screws, and you don't want them shearing off. Use an India stone lubricated with a bit of oil to hone the underside of the gas key to make it completely flat so it'll make a good seal with the carrier. When you're done, the underside of the gas key should be completely shiny around the EDGES. Some non-shiny spots in the center of the underside are OK. Clean it thoroughly with degreaser.
CARRIED AWAY: Apply Loctite 638 retaining compound (not thread-locker!) to the underside of the gas key, doing your best to keep it out of the gas port. Position it on the carrier, lining up the screw holes in the key with the carrier's. Now, put a dab of oil on the threads of each of the new gas key screws, and screw them hand-tight into the carrier.
Grab your adjustable torque wrench and tighten both screws to 50-58 in.-lbs. Hit the inside of the gas key with a shot of canned air to blow out any Loctite 638 that might've oozed into the gas port.
STAKE IT LIKE A VAMPIRE: Staking the screws is easy when you use the Brownells Gas Key Staking Tool. The tool will cost you a bit, but it's a once-in-a-lifetime investment. Apply a dab of grease to the threads of each screw to preserve thread life. Secure the carrier in the tool and hand tighten the staking screws. Make sure the pointy tips of the screws are centered over the gas key screws.
Clamp the tool in your bench vise. Put the correct-size bit in your driver and tighten the staking tool's screws. Look down through the top of the tool to watch the staking notches form. If you use an adjustable torque driver like the Fix It Sticks driver, you can see how much torque you applied to the first screw, so you'll have a good idea how much to apply to each of the three other screws. How much torque you'll need depends on the hardness of the gas key's steel and the type of finish on it. Once the staking notches are made, back out the staking tool's screws so you can remove the carrier from it.
That gas key is now "PROPERLY STAKED" and snugly (not snuggly!) fitted to the carrier with a leak-free gas seal. Isn't going to move anywhere.

[@pauldowning3996]

Meticulous attention to detailed craftsmanship and hair.

[@ThePatriotParadox]

That's not just regular nitride, that's gotta be Melonite (QPQ) OR DLC coating.

[@briankopp1369]

One of my mean quirks is to tease him about the brand of axle grease in his hair, I recommend green grease, my favorite for everything. Not joke green grease is the bomb.

[@ThePatriotParadox]

@@briankopp1369 frog 🐸 lube is supposed to be awesome.AND GREEN..LOL...do you know about lube and cleaner? I got some Cleanzoil and says is degreases.. but also say good for finish and mainly cleaning AND lubrication? Seems to work well, but kinda sounded contradictory

[@TheREALLibertyOrDeath]

School of the American Rifle

[@brownells]

Chad is a great guy and good friend of ours.

[@SchooloftheAmericanRifle]

​@@brownellsthank you very much. The sentiment is mutual.

[@danikpew596]

I can't even count the amount of times your channel has helped me. Top notch per usual. Thank you

[@derekhall7610]

I love your teaching methods... now I know... and knowing is half the battle lol

[@jdmznet]

Just don't forget the red lasers and blue lasers. ;-)

[@derekhall7610]

@@jdmznet and no one ever got shot

[@justinhoffmann4464]

I'm a new gunsmith, and your video help me learn do this. So thank you very much. My instructor showed us how to make make this tool, but he did not show us how to stake this part.

[@feedinc2735]

I'll be damned... I never knew so much went into a gas key. I've always bought complete BCGs. Good job.

[@joesaad3089]

Watching this tutorial was a pleasure

[@georgemoomaw9437]

ANOTHER great, informative instructional video from Brownells

[@pistolgrips]

Very thorough and easily understood. Thank you.

[@doejohn8674]

Excellent video, clear explanations as always!

[@henrycalhoun5809]

An excellent presentation. I now know I need to learn more.

[@Z7d3nR4]

Nice video. Thanks, Bob. Glad you didn't have any happy accidents.

[@tonykees9044]

Thanks for the lesson

[@omarponce9412]

nice and clear. good job.

[@Docsporseen1]

Just for added info, you should never use the Fix-It Sticks torque driver to loosen screws like he did. It messes up the torque settings and eliminates the warranty.

[@stephen6640]

Great catch 👍

[@analogludite9575]

I thought I saw him do that.🤔👍

[@rdtowerberlin3995]

NEVER use a torque wrench/screwdriver to break torque.

[@rustytaylor7708]

Great video

[@dragonsofthunder]

I'd just buy a new entire bcg. This is a great video though brother

[@scott2228]

Exactly what I was thinking. Then throw the old bolt carrier into my ever growing parts bin.

[@timrobinson6573]

I would just throw my rifle in the trash can and buy a new one.

[@dragonsofthunder]

@@timrobinson6573 🤣🤣🤣

[@Sparks00psn]

@@timrobinson6573 🤡 🎉

[@toddparsons2980]

Very informative.

[@wc4201]

Great vid. Thx

[@toddm9501]

Great Job!

[@theOriginal_ex811]

Really digging on your happy little trees, man.

[@douglass69]

It would be really nice for I think most of us if you would put a still shot close up in the corner while you’re talking about the parts.

[@celtspear6903]

I was very impressed with that demonstration of how to correctly replace the gas key. I paused the video to go to the website and order the staking jig for myself. It seems like a common sense tool to have around if you enjoy working on and modifying guns as I do. Thanks again for the great demo!

[@64samsky]

Thank you!

[@para1324]

Watched on U Tube. Well done great explanation. Appreciated. 👌👏

[@ChatGPT1111]

Ummm, this is You Tube 😂

[@Akilles3]

Solid info as always, thanks Brownells. RPG in the safe... 👀

[@ocd_ar1598]

Great video as usual, thank you- the other sealant often used while installing the gas key is Permatex Aviation Form a Gasket (#80019). Steer clear of getting anywhere near the gas hole with this sealant.

[@chrisd5758]

Considering it goes around the gas hole, it's going to be near it.

[@TriggaTrey361]

@@chrisd5758lol just compress air it out

[@deezTX]

nice job

[@bdf429]

I just discovered that several companies make an adjustable AR-15 Gas Key and Brownells has one for sale. I would be very interested in seeing a video about these keys and what makes a good adjustable key specify how is the adjustment locked and secured to not move after it is set.

[@jamesrobertsable]

thank you sir.

[@ssnydess6787]

I love your videos; taking us to the next level. How about using some glass and lapping compound?

[@mnrodriguez]

Awesome!

[@Beanmachine9198]

Excellent my friend, you need to come home, get some S. Louisiana sun, and give me some tips on a very old AMT 380 BU😎

[@ralphjohnson8775]

That's a really nice stone for that job. I might pick 1 up sometime. I use 620 locktite on my gas keys and break cleaner non c Version to clean Under the gas key dont forget the gloves.

[@CalebDor]

Very good presentation. I had wondered what the procedure was for replacing a gas key correctly on an AR-15. Thank you. By the way, is that an AT-4 in the open locker in the background? I haven't seen one of those in years. Take care each of you!

[@stephen6640]

Nice video, one SAFETY concern though. When using compressed fluids or gasses you really need to wear safety glasses. Oul in the eye sucks.

[@Ash_95]

Takeaway is never be satisfied with a cheap screw. Go for the quality which, apparently, Brownells can hook you up with.

[@oscarpuente2029]

outstanding

[@chrishesotian1654]

this is exactly how Chad from School of the American Rifle teaches it!

[@generallee4043]

Young manufacturing produces some of the highest quality bolt carriers and proves that there’s no need to stake a gas key if torqued to 59 inch pounds

[@cheeto4240]

could you do a video on keyholing and potential causes?

[@donaldhollingsworth3875]

What grit of stone(s) are you using? As a machinist, we used stones on tables & face plates along with the fixtures.

[@chrissewell1608]

Replace it with an Unobtainium model! They are WAY FASTER!

[@custom20chevy]

Thanks for the quick tip! (3 hours later.....spongebob) Excellent video as usual Caleb

[@charleshurley2582]

Great video. BOUGHT THIS TOOL FROM BROWNELLS SEVERAL YEARS TO HAVE, "JUST IN CASE".. NOW I KNOW HOW TO USE, WHEN NEEDED THANKS...

[@maverick9708]

Note that if you lap your gas key it's important to apply even pressure. Also I think the other sealant people like is the Indian head gasket shellac

[@mattfleming86]

Say what you want to about bedding looser fit extensions.. it works. I only needed to do it once but an instant reduction in groups from 1.5-1.75" to 1" told me all I needed to know. Later used that (reputable higher end brand) upper in a different build and the barrel popped right out with a wooden dowell and a single smack with a mallet. It worked for the a Army Marksmanship Unit, and it worked for me. Then again I think you know this, you just like the free comment you get every time you mention it :-D You're right everywhere else on loctite though. It's important to remember that 638 and it's cousins aren't a threadlocker.. just a heat resistant "gap filler" Bubbas out there have defiled the Loctite name lol.

[@hairydogstail]

The barrel nut constricts the upper barrel channel around the barrel extension, much like a muzzle device will constrict the bore with higher torque..I have seen .003 constriction with 50+ barrel nut torque.. Considering most modern machined uppers are under mil spec 1.00 to +.002 and run tighter from .9990 to .9980, the mill spec barrel extension tolerance is .9987 to -.0008, the constriction itself is more than enough to stabilize the barrel..Throw in a thermal fit upper .9960 and it is quite redundant IMO to bed the barrel..Sloppy milled uppers is another story all together where shims come into play..The other side of the coin is it doesn't hurt anything other than making it harder to remove the barrel..

[@mattfleming86]

@@hairydogstail That one barrel/upper combo was the only one that "needed" it, and it certainly worked. With the number of manufacturers we have out there it's bound to happen eventually to anyone who builds enough guns. Handy trick to have in the toolbox.. plus if I need to tighten up a bearing on a piece of farm equipment I still have most of a bottle.

[@Chef-James]

I like the torque wrench. You can back out screws with it?

[@timrobinson6573]

Can you do a video on when it is appropriate to use Loc Tite on an AR? Larry Potterfield, the owner of Midway USA, who is a master gunsmith, put out a series of videos about 10 years ago on how to build an AR. He used Loc Tite throughout the build.

[@brownells]

We did it, kzbin.info/www/bejne/qYeng2B3p9qtg7M. Yes, the Midway video is considered wrong by many industry professionals.

[@semper.fidellis]

@@brownellsshots fired! 💥

[@AndrewTPewPew]

What grit are the India stones you use for that work? Great vid btw! More content like this please :)

[@Captain_Spaulding_01]

1000g would be ideal

[@williamwinn948]

You can use a diamond stone to level your regular stones.

[@jebbuhdiah-dean]

@brownells Thoughts on/experience with the Optimized Carrier Key Screw (O.C.K.S.)?

[@cliffcollins2497]

Finer than frog hair. Thank you and take care!

[@mangamaniaciam]

Mr. Caleb: Would you recommend DMT extra fine diamond stones for this leveling process? I know that the diamond stones are the most level surfaced materials made. And getting the bolt carrier group level is a must.

[@chipsterb4946]

What is that nifty bit driver? Nvm found Fix It Sticks - not sure if it’s any better than the Wheeler Fat Wrench I already have.

[@mrshort2379]

great info great content: I have to ask though what are your thoughts on an adjustable gas key, such as benefits and pro's & cons?

[@chipsterb4946]

Do you mean adjustable gas block?

[@Pyreleaf]

I know you're not asking me, but in my admittedly amateur opinion, I would think if you want to regulate your gas pressure, you're almost always better off sticking with an adjustable gas block, just because it's much easier to access and make adjustments.

[@arlissyoung8899]

Don't worry, I didn't know we had so many Super Master AR Rifle builders in the U S. I am amazed at the number of people. Well I build rifles all the time, I have built thousands of ARs, On my next Super AR build I, On my last Super AR build, I only use Super part so and so on ALL my AR builds, Then the super list of ALL PARTS are listed down to the oil used when finished. Then there's the line of people standing outside their door, I need you to build me another Super AR, That's the best one ever. I can't believe retail stores are even able to sale ARs we have so many Super Master AR Builders. On my next build, On my last build.

[@brownells]

Beautiful poem...

[@hairydogstail]

How do you say I don't understand the AR platform without saying it?

[@jerryparker5137]

I replaced a lot of gas keys but its been a long time since I have replaced or installed a gas key. I just need a review

[@Ordieguy95]

What is a good bolt carrier group.

[@jerryparker5137]

I always replaced the screws with new ones

[@ovclay]

Where do I find that tool kit used in this video?

[@Xion431]

what kind of grind stone is that?

[@cd4498]

I had a gas key come loose once. I retorqued them by feel and went over the stakes with a screwdriver ice pick punch thing i had laying around then marked the screws for future reference. Hopefully she holds but so far so good.

[@5jjt]

Remember, "wet" torque value is about 25-30% below "dry" torque values.

[@krugerdw]

This might be a stupid question, but is it a bad idea to use a torque limiter when you’re breaking a bolt loose?

[@Docsporseen1]

Yes. Fix-It Sticks notes that in the instructions.

[@warthogjj]

What grit is your India stone???

[@ryanthorne5432]

I’m looking at TM 9-1005-319-23&P, and there is not any thread locker specified. This does not mean that thread isn’t a good idea, however. There is a specification on staking, which calls for 0.025 inches, or less, of metal protruding above the surface. One thing I didn’t hear Caleb say is that carbon will create the final seal between the gas key and the bolt carrier body. If you have to manually cycle the first few rounds after replacing the gas key, that doesn’t mean you messed up. Give it up to 8 rounds before you decide that the replacement of the gas key is a failure.

[@tractormanx5954]

I would think you would mic it before and after to see how much you actually take off

[@brownells]

Why? Flat is flat.

[@SchooloftheAmericanRifle]

Tractormanx5954 I'll bite. Tell everyone how much is too much.

[@brianleabo6295]

My ocd would kill me with this

[@tomsakowski1162]

How would you stake a key for a AR308/AR10?

[@ChatGPT1111]

Exactly the same only completely different 😂

[@sportsmanslegacy]

Is the new gas key not CNC machined? How is it that the stone gets it flatter than the cnc machine

[@jasoncarson8606]

machining tolerances vs water jet cutting tolerances.

[@JohnTBlock]

You've stoned the key bottom, BUT, what if it's channel on the bolt carrier is not flat?

[@slister1911]

It's not perfectly flat, but it's flat enough that the Form-A-Gasket makes a seal around the gas hole. This truing of the carrier key is not necessary.

[@steemerxaxon1643]

Just put the RED Locktite on the bottom & Screws & NO WORRIES

[@RobinP556]

So, serious question. You’ve put time and attention to making sure that the flat on the gas key is perfectly flat but done nothing to the bolt carrier, why do the work to the gas key? I know that the 638 takes up any gap, it just seems like paying that much attention to the gas key but not the bolt carrier is lost time.

[@SchooloftheAmericanRifle]

50% improvement is better than good enough.

[@C_oprator89]

Them yfs bolts? I know I know

[@torito90]

Can anyone help tell me what torque screwdriver he was using in this video. Thanks in advance?

[@oklahomahank2378]

Fix it Sticks.

[@un4getable609]

Where do i find videos on the brownell website?

[@CalebSavant]

"Trigger Times"

[@FierceMouse]

$99 SALE--Brownells chrome BCG with/without serrations (both m16 and ar15, so get right one) I do not work for Brownells, I just like good BCGs

[@chrissewell1608]

Tac weld it on there buddy!

[@shawnparrish1999]

How do you know the carrier side is completely flat?

[@NoWr2Run]

You don't that' why you use Loctite as a gasket. You could get a small straight edge & see if it's COMPLETELY FLAT. I use a STARRETT 6" ruler.

[@matthewdropco]

What grade of Steel wool? Thx!

[@brownells]

#0000

[@matthewdropco]

@@brownells Thx!!!

[@masonj0627]

Using a Fix-It Stick torque limiter to loosen the gas key screws? Say it isn’t so? 😳

[@slister1911]

Truing the carrier key removes the protective phosphate and is not necessary, nor mil-spec. Colt doesn't do it, FN doesn't do it, no major manufacturer does this. That's the whole point of the Permatex No. 3D Aviation Form-A-Gasket liquid. Also, the Key and Bolt Carrier Assembly Drawing 8448505 specifically states that the Form-A-Gasket is to be applied around the gas hole only on the carrier prior to assembly, not around the key screw holes (Note 2). Whether the method in this video is superior to the M4 drawing spec, and the millions of carriers that have been assembled accordingly, is up to you to determine.

[@seafarermarinesupply9869]

638 is anerobic. any thing exposed to air will not cure, its only good to 350f. im sure that key sees way higher temps than that when mag dumoing or even tust 30 round strings.

[@feskymaloon1439]

The gas key doesn’t get that hot. I’ve pulled the BCG out immediately after 2x 30rd dumps and I could handle it by hand. I don’t know WHY it doesn’t get that hot, but it doesn’t.

[@jackieow]

Loctite says #638 takes a primer, so why aren't you using a primer?

[@johnphillips222]

This is so funny. Loctite 510 used as a flange sealant, not some retaining compound.

[@oklahomahank2378]

I always put on nitrile gloves before using Gun Scrubber. That stuff works great but has some seriously nasty chemicals.

[@JJheadcharge]

So, for the price of a new gas key, staking jig, stone, etc. might as well just buy a new BCG

[@brownells]

Yes, unless you have a KAC Sandcutter, like the one used in the video or plan on repairing multiple.

[@5thPlaceAce]

Did somebody say Steak!?

[@jman26388]

😎💪🕺

[@tenmiltenmil1770]

❤️❤️❤️👍👍👍⭐️⭐️⭐️⭐️⭐️😊😊😊

[@Iceaxehikes]

I tried to tighten the gas key on my Mini 14 and realized; the superior design of the Ruger Mini 14 doesn't require a gas key. Hmm.

[@adventurfly879]

I saw the bolt carrier you were working on and my insides were screaming noooooooooooo! Those arent easy to find and arent cheap

[@CalebSavant]

Yeah, but if it eases your pain, this one is non-serviceable. There is a ring in the bolt channel that tears up gas rings, so we had to decommission it.

[@adventurfly879]

@@CalebSavant oh, thank god.

[@chriscox5568]

I hate to throw a negative comment on your video and alot of your other videos too but your cameramans recordings have a lot to be desired. He never gets up close and tight with his shots so everybody can see everything just like we all was therewith our eye's about eight inches from what your showing us what your doing ! He needs to get in there extremely close with the zoom lens so we can see and have plenty of light in the darkened areas too or your just waisting your time and ours too !

[@JohnFree007]

Just buy a new bolt carrier!😅😅

[@scaler1179]

Besides staking, I also use Rocksett on the screens. Unlike red Loctite, Rocksett is designed to be heat resistant.

[@TheDiameter]

You have melted your gas block or warped your barrel before you’ve degraded red locktite on the bolts of a gas key… or you’re on your 10k round mark

[@scaler1179]

@@TheDiameter or firing full auto... a lot.

[@SchooloftheAmericanRifle]

If you shear a screw and use threadlockers, it's harder to remove the broken fastener.

[@davetremaine9763]

Just clicked on the video, if I don't see Linus I'll be very upset.

[@mawilkinson1957]

I can't see where you would ever, have to change your gas key. Simply maintain the original. Keep it clean.

[@hairydogstail]

Mill spec for the gas key is Permatex's Aviation Form-A-Gasket No. 3 Sealant Liquid..I still prefer Green loctite as it seals better IMO..

[@Sparks00psn]

Gas keys are supposed to be permanent. If it’s time for a new gas key get a new bolt carrier.

[@SchooloftheAmericanRifle]

Nope

[@Sparks00psn]

@@SchooloftheAmericanRifle k