16" Bushmaster "M4" Dissipator barrel
WOA Upper
RRA Carbine Gas tube

Installed everything to spec. Proper torque. Proper gas tube insertion, and pinned. Opening of gas tube was on the bottom, as it should be.

Gas rings aren't aligned. The Carrier Key is tight and staked.

The lower used is a lower I've been using off of my M4 carbine. Well over 3k rounds through the lower without problems.

The problem is the bolt on this new upper isn't cycling. It isn't short stroking or anything at all.

I'm gonna spray some lube through the hole on the gas block and see if theres even a gas port drilled.

That'd really chap my ass... Any other ideas?

Interesting......

Did you install the gas block?  Or was it "installed" when the barrel was purchased.  Could be a misalignment of the gas block and hole in barrel....  All it takes (so I've read) is to be just a hair off....

No blocks in the gas tube?  If need be, remove and spray w/ liquid to see how much flows....

But the upper hand cycles fine?  No binding that you are aware of...

Post this in troubleshooting.  Tweak and Dano, and others, are on stand by, and will be good help.  
Sounds like you're obstructed, not passing gas.

Spray some brake cleaner through the upper gas tube port and see if it comes out the barrel.

I don't know all the specs for barrel length and tube port sizes but not cycling at all sounds to this novice like a gas problem, or a serious carrier problem that you probably would have noticed.

It would not be the first time that there were manufacturing (or assembly?) errors.

Good Luck.

Rick

Addendum:  My Thing is trying to bring together those elements that make for an accurate rifle with those that make for a reliable rifle, issues not always the same, but usually very compatible.

With this in mind, there are periodically reports in the precision rifle world of "top quality" barrels showing up with all kinds of problems.  I have in mind a high dollar, precision, Service Rifle Barrel Manufacturer who let out a barrel with the gas port drilled off angle, to the proper depth, but as a result only allowing a fraction of acceptable gas pressure.  

The rifle would function OK when fresh and clean, but when slightly dirty would not cycle consisently.  It took a good Journeyman Service Rifle Shooter a year to problem solve it.  He was chagrined, but it could happen to anyone.

Your Bushie barrel is probably fine, but they have had production pressures and YOU should be the determinant of your barrel quality.  (I like Bushies, truth.)

Check your barrel drillings.

Is the gas tube a quality tube?

Did it get tweaked between receiver and barrel?

Is the ammunition and/or buffer an issue?

These ARE machines.

Best Regards,

Rick

Great education for "The Rest of Us."  Thank You!

Quoted: Addendum:  My Thing is trying to bring together those elements that make for an accurate rifle with those that make for a reliable rifle, issues not always the same, but usually very compatible. With this in mind, there are periodically reports in the precision rifle world of "top quality" barrels showing up with all kinds of problems.  I have in mind a high dollar, precision, Service Rifle Barrel Manufacturer who let out a barrel with the gas port drilled off angle, to the proper depth, but as a result only allowing a fraction of acceptable gas pressure.   The rifle would function OK when fresh and clean, but when slightly dirty would not cycle consisently.  It took a good Journeyman Service Rifle Shooter a year to problem solve it.  He was chagrined, but it could happen to anyone. Your Bushie barrel is probably fine, but they have had production pressures and YOU should be the determinant of your barrel quality.  (I like Bushies, truth.) Check your barrel drillings. Not sure yet. Will check on Monday when I can bring my tools home from work. Is the gas tube a quality tube? Yes Did it get tweaked between receiver and barrel? No Is the ammunition and/or buffer an issue? No, because its the same ammo and same lower I used on my other upper, which functioned fine that night even. These ARE machines. Best Regards, Rick Great education for "The Rest of Us."  Thank You!

Barrel looks immaculate as far as outside appearance. Nothing looks to be lacking as far as quality. My only guess is the gas block could be out of alignment, or the lack of a port



The action hand cycles with ease. Nothing gritty. Everything was cleaned and lubed prior to shooting.

The gas block was installed prior to me getting it. It was a barrel ordered direct from Bushmaster.

Fluid flows freely through the gas tube.

Thanks for the help...

Still could not get fluid to flow from the gas block to the barrel. So now the question is... Send it back to bushmaster? Or hammer the pins out and look for myself?

Then if it has nothing or it's misaligned.... will bushmaster fix it if I've tampered with it?

If this barrel has a gas block, and not a FSB with sights, then you need loosen the set screws and check the block index against the  gas port (read both cant, and position off the barrel shoulder).

If this is a FSB with taper pins, pull the gas tube and try to flow CLP threw the port without the tube.  If its a no go and the CLP will not flow into the bore, send the barrel back to Bushmaster and see if they can find one that wasn't built/assemblied by a drunken monkeys  (must have been a lay off at the Romanian SAR plant and they got extra helpers really cheap).

If you can narrow it down to a barrel/gas block/gas port issue, send it back.  Don't mess with it and give them an excuse to mess with you.

Quoted: If you can narrow it down to a barrel/gas block/gas port issue, send it back.  Don't mess with is and give them an excuse to mess with you.

Thats what I'm thinking.

No gunpower residue in the gas tube.. and I fired 2 shots.

Nothing came out of that gas block. Guess I'll remove it from the upper and give them a call...

UPDATE::

Ok Kudos to Bushmaster. Today they gave me my RMA number, and a prepaid shipping label to send it back.

They're gonna swap it for a new barrel and have a qualified gunsmith check the alignment of the gas block and FSB of the barrel with some sort of optic tool, then run air through the gas port/block/tube to make sure it's working to spec.

And to top it off, the guy was friendly and nice.

Quality customer service. A+

So, as an AR novice, I've got this list of most common AR problems and fixes going.  

Gas Keys/bolt cam pins  seem to be right up there.  I have added Front Sight/Gas Block Assemblies.

Gas seems to be a theme.


I think that anyone who expects an AR to do it's thing  all the time should be a mini armorer. That's my plan.

Yeah, a mini me!


Clint Smith said something at a handgun class I had the opportunity to attend.  Essentially, " If you get a handgun that works well, that's great!  Get another one just like it!"

I think that's true for a rifle as well.

I just bought another lower parts kit, bolt assy, and trigger assy. Think I'll stick with RRA for now cuz that's what I have. I see another rifle in my future. (Plug for RB Precision +1 inserted here).  


Let us know how it goes, JE3146.

Glad to hear that Bushie is helping out. Good thing. Not surprised.  

Regards,

Rick