New member but I have been reading for a while.  The information gathered from this site has been substantial.  Yet I still am having trouble with an AR I just put together.  The barrel was very accurate but it was a single action.  It ejected the spent cartridge and that is it.  Had to manually cycle a new shell.  Shot it maybe six or seven times and it happened every time.  18" Wilson Combat rifle gassed barrel, Toolcraft nickel boron bolt, Anderson carbine buffer kit.  Everything is clear no shavings, burs or clogs.  The barrel is dimpled so I am not sure how the block wouldn't be aligned.  Was shooting 55 grain American Eagle.  I am not new to AR's but this is the first one I purchased each piece and put it all together. I've read that drilling the gas port in the barrel is a last resort but what else is there to do?  I have ordered heavier ammunition and plan on going to range Friday and have someone video the bolt and see what is going on.  The barrels gas port is 0.09 inches.  I know this topic has been posted before and I have read them all and I still don't know what to do other than run it wetter, hotter ammo and if that doesn't work drill out the port.  Let me thank you all in advance for any suggestions and for all the help you have provided this past year while I developed a full blown addiction to searching for deals on gun parts and checking tracking orders on UPS.com 30 times a day.

Check to make sure the gas rings on the back of your bolt are staggered so the gas cannot just pass through.  I've heard some folks say it doesn't matter but it stopped my brand new Bushmaster from running a long time ago.  

Edited to add - also check that the gas key is not loose on your BCG.

Do you know if the bolt is moving at all when you fire?

Wilson is good stuff, I doubt the barrel port size isn't correct (but not impossible).  

If everything is lubed and freely moving...

Start by eliminating your variables.  If you have a known working good BCG, put it in and shoot it.  If it works, problem is with the BCG (likely key or rings).  If it doesn't work, put the original BCG back in and swap in a known good working buffer and spring and shoot again. Continue with this process of elimination with individual components in each group, based on the pass fail of the test until either it works, or you have established that the rifle is under gassed (IMHO least likely scenario.)

ETA:  first look at your gas block.  Fixed or variable?  If variable, adjust.

you stated that it is ejecting the spent casing. does it lock back on an empty mag? are you quadruple sure you installed the gas block correctly? could your spring/bugger setup be too heavy? as another posted stated, double check your BCG for loose gas key or bad rings.

Pop a weight out of the buffer.

Had it happen with one of my builds once and it required a little work on the sear as it was getting hung up on a burr

How heavy is your buffer?
Gas key tight?
Well lubed?
Noting there is a dimple for the gas-block screw is not the same as verifying alignment of the ports. Verify.

Does the bolt cycle smoothly when you operate the charging handle?

Rifle-gas on an 18” barrel is already cutting 2” off the normal dwell time so you’ll need a gas system that’s in excellent condition.

Was this one of the barrels Wilson was blowing out around black Friday? I had the same issue with both barrels I bought from them at the time. One was the Urban Sniper 18in with rifle gas system.

I couldn't get it to cycle unless lowered the buffer weight in a carbine buffer system, yet it works fine with a rifle buffer, tube and spring.

18" rifle gas can be sensitive, since it does not have as much dwell time in front of the port.  Some barrels are designed to be "soft shooters" in this configuration for 3gun competition, and suffer with any additional buffer weight, extra power springs, etc.

First, function test.  Can you easily manually lock the bolt back using the bolt release?  If not - there is a parts issue not allowing full rearward motion.

The way to test ANY AR15 gas system, should be a ONE cartridge in the magazine.  Fire.  Does it lock back on an empty mag?

If not, then the problem is short stroking.  If it does, then your issue is likely magazine related not feeding the next round fast enough.

If short stroking, there are MANY causes.  Gas leak, improper lubrication, binding/friction, improper gas port.

Save the "gas port" solution until you are an EXPERT, or have had an expert review everything.

Start with the easier thing first.  Lubrication.  Do not use any grease or heavy lubricants.  Use something well know for the AR like CLP, CLP equivalents, or Motor oil (any weight is fine).  Lube the important areas per the technical manual and re-test.

Next, binding/friction.  Look, listen, and feel as you pull the action completely open using the charging handle.  Common issues would be related to the receiver extension (buffer tube), spring, buffer.  Are you using standard, milspec parts of fancy aftermarket stuff here?  Carbine buffer tube?  What weight buffer?  What kind of spring?

Next, gas leak.  Its rare on new parts but it happens.  Verify your gas block is snug and look for air gaps using a flashlight.  Check to ensure the bolt carrier key isn't loose (rare on a new build, much more common on an aged one).  Check the bolt to make sure you have 3 gas rings and lubricate this area liberally.  I don't buy into the gas rings staggered stuff - its mostly mythology as the gas rings rotate themselves when you fire it, and I have lined them up intentionally and could never get a weapon to fail.


Pictures of your buffer, spring, receiver extension?

I checked the gas rings after the fact and they were not lined up.  Key is solid.  Bolt ejects the empty but does not feed.

I have a couple other bcgs and lowers I will take to range Friday.  Its a fixed block.  Just want ideas on a plan for Friday and hopefully get this fixed.  Bugs the hell out of me.

If you have a lower with a rifle extension, I'd try that.

I didn't check on the empty mag.  Fired it 5 or 6 times and put it up and pulled out another because I was wanting to shoot.  On my list for Friday.  The barrel is dimpled and its obvious when one of the set screws is in the dimple as it sits lower so I am not sure how it could be off but I am not sure.  If you are in the dimple can you still be off?  How do yall set your blocks so you know they are perfect?

3 ounces on the buffer.

its a 3 ounce buffer but if everything is lined up then gonna have to be spring or buffer I guess.  Thanks

Didn't think of that.  I cycled it manually maybe 100 times today just to loosen things up.  I've looked around and havent noticed anything but I will check again.  thanks

Buffer is 3 ounces.  Key is tight.  Seems smooth when I charge it manually.  It probably could have been wetter.  I will verify block is aligned, I hope that is it.  Thank you.

I ordered it 11/21 and it is the same style barrel you have.  So you just installed a riffle buffer and it runs good?

3 ounce buffer.  It was an Anderson buffer kit so nothing fancy.  It runs fine by hand and that is a reason I don't know what it could be.  The bolt will lock open manually no problem.  Other than verifying the gas block is aligned because I did just eye ball it and made sure the screw was seated in the dimple.   Thanks.  I feel like I know what to

When I switched out the carbine buffer, tube and spring over to rifle it worked fine.

Someone in the thread also suggested taking a weight out of the buffer. Mine ran better after doing that as well, if you're set on using a carbine extension.

I still can't get it to run cheap steel stuff, but what I'm using seems underpowered anyways.

I challenge everyone to try this. It's simply a waste of time. Once you fire one magazine or less through your rifle the gas ring splits will naturally come into alignment. The rings work fine if the gaps are aligned or your rifle wouldn't run at all after a magazine or two.

Check the gas tube. Is it fully inserted and pinned? Is it installed upside down (straight gas tubes only)?

Check the gas block location. Is it centered directly over the gas port, or was installed too far to the rear or too far toward the muzzle?

All gas ports in gas blocks are drilled from the bottom up making it easy to align properly. Most barrels have a dimple directly under the gas port to locate your set screw. It's easy to remove that screw and look at the alignment without disassembling the upper.

Failure to cycle the bolt is a gas problem. It appears from your post that you aren't getting any gas at all.

If you have an adjustable gas block adjust it for maximum flow.

Back in the mid to late 90's I had a brand new Bushmaster that wasn't self loading.  I took it home, read the trouble shooting section of the manual and it said to check them.  I found them aligned and staggered them.  Took the gun to the range the following day and it ran fine.

That was my experience with that brand new Dissipator. It fixed my carbine so I figured I'd share.

Take your rifle apart and look where there are aligned now. Every time I field strip a rifle the slots have naturally aligned.

I’m slightly confused....

You have a carbine buffer tube and a 3oz buffer?
You have a fixed stock or a non adjustable gas block?

Carbine buffer tube, 3 oz buffer, nonadjustable block. I swapped out the Anderson buffer kit with an Aero one, oiled the hell out of bcg, checked block alignment and tried it again. It ran great, locked open on empty mag, until I started shooting steel. Anyway no drilling barrel needed. Thanks for the tips.

I've found that the quickest way to verify gas block alignment is to go to the stationary store, get some canned air, and a soda straw or rubber tube.  Remove the BCG and use the air on the gas tube.  you can move the gas block around and hear the difference in the barrel.  Align for best flow and you're good to go.

This hasn’t been my experience on my ARs or the M-4s i was responsible for while i was a unit armorer. Even after a few hundred rounds on a range i never saw any bolts with the gas rings all aligned with each other. That being said, i do agree that alignment of the gaps doesn’t make a difference in how it operates. Never have i seen an AR platform fail to function because of the gaps of the gas rings being aligned.

I agree with you and had same thing with an A2.

Confirm gas tube is oriented  correctly,  make sure the gas tube hole is down. Don't  ask me how I know!!!