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Discussion Starter · #1 ·
I have an AR but it was a factory build. I built my first ever with my own hands AR15 this past week. 18" barrel and all the parts hand picked within my budget. Its not a $3000 beast but for me its a big deal. Other than wanting a longer barrel than my other AR I also wanted to see how much I could lower recoil. 556 doesn't have much anyway but I wanted to see how little recoil I could achieve. So I used an adjustable gas block and a Strike Industries King Comp Dual Chamber Muzzle Brake. 1st day at the range was yesterday. I was happy to see it fire. I never built a gun before. However it didn't cycle the next round. I knew I had to dial in the gas block so for the next 30 mins. I'm tweaking it. Got all the way to wide open 100% and still it won't cycle. Well shoot! So back home I blow canned air through the bolt carrier end of the tube and it definitely is not a misaligned or pinched gas tube. Could my gas block be faulty?
Out of ideas I start suspecting the only other item that manages gas: the muzzle brake. I figured if I ruled that out then I'd go through the hassle of replacing the brand new gas block. So I unscrew the muzzle brake and put on a simple $9 A2 birdcage. Hit the range this morning and it cycles like a champ! Even with the gas block as closed as it can go!

I'm disappointed in how this worked out though. Even though I could only get off one shot at a time with it on wow what a huge difference in barrel movement that muzzle brake made.

If anyone has suggestions for either a low profile block known to deal with a muzzle brake or maybe a muzzle brake known to not cause gas issues please do share.
 

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I hear what you are saying, and I am not the most knowledgeable ar guy here, but I have built a few. I don’t think the brake is the issue. By the time the bullet gets to the brake, the bullet is in effect out of the muzzle regardless of the muzzle brake, and if it’s out the muzzle, it is past the gas port. I wonder if you had something misaligned when you went to the range and when you checked it over following your cycle issues, you fixed it. Also, was it the same ammo? What load are you shooting that is giving you issues and what is your gas system and buffer combination?
 

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Discussion Starter · #4 · (Edited)
I hear what you are saying, and I am not the most knowledgeable ar guy here, but I have built a few. I don’t think the brake is the issue. By the time the bullet gets to the brake, the bullet is in effect out of the muzzle regardless of the muzzle brake, and if it’s out the muzzle, it is past the gas port. I wonder if you had something misaligned when you went to the range and when you checked it over following your cycle issues, you fixed it. Also, was it the same ammo? What load are you shooting that is giving you issues and what is your gas system and buffer combination?
I had never heard of it either. Same ammo. It was like day and night between the A2 and the brake. Made no sense to me either. I thought I understood that the gas that far up was already expended past the block.
55gr .223 Winchester fmj - I only had that with me in the can I brought. Fires just fine in my other AR and this one with an A2 end. I will bring other brands next trip too if I swap the brake back on.
Parts:
Aero Precision Low Profile .750 Adjustable Gas Block - Nitride - APRH101614C
NBS Stainless Steel Gas Tube - Rifle Length
Aero Precision AR-15/M4 Carbine Receiver Extension / Buffer Kit - APRH100151C
Aero Precision C158 SP/HPT/MPI 5.56 Bolt Carrier Group

I expected surprised replies. Now you have me considering reinstalling it again just to confirm I didn't "accidentally" fix the gas issue somehow before I switched muzzle ends.
 

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A muzzle brake causing gas issues?
Not really but……..When I was in Texas Kenny I had neighbor who was a gun guy and had an AR10. It shot fine…until he put the break on and then it short cycled. The only thing the two of us could come up with was the angle that the gases were taking, (angled backwards to eat recoil) was canceling out what the gas system was trying to do. The gas system is trying to push the BCG back while the break is trying to push the entire rifle forward. He opened up the gas system and nothing changed. We both agreed that a liter buffer spring or a liter BCG may fix it. Downside is I moved back to STL so I don’t what the
outcome was.

I bet if you Google it you’d find something.
 

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Well, i will lend my AR knowledge since i am very familiar with them.

I do not think its the muzzle brake either. It should have no effect on the gas pressure. Now if it was a suppressor thats a different circumstance since that increases pressure.

I feel it may be a gas block issue. If i run an adjustable i only use SLR sentry adjustable gas block, S7, S8, S9 models, it has detent positions that lock positively. Keep in mind gas pressure changes with different makes of ammo. I only have one that will cycle steel case wolff, the rest wont.

Check the alignment, is it clamp on or set screw mounted? I always stake the barrel on set screw type blocks, then red loctite them in place. If the block is fully closed you should have no gas pressure, and gun should become a single shot rifle, and will have to manual eject the spent round. Sometimes might have to mortar it.

Keep in mind buffer weight, and bolt carrier type also come into play. A 5.5 oz rifle buffer, H2, H3, versus a standard carbine buffer which is lighter. The m16 bcg is heavier than the commercial ar15 bcg. Reduced power springs can effect it as well.

Make sure the gas tube is clear, installed correctly with its roll pin. Make sure the gas block is secure and perfectly aligned.

Another thought could be if the gas port is the correct size on the barrel. It can be wrong, it happens. What barrel maker did you use?

Just a few things that come to mind. I wish i could put my hands on it, likely i could remedy it in 15 minutes.

Also remember a new rifle needs lots of lube on the bcg. Running it dry can make it malfunction alot, it should loosen up between 150 and 300 rounds, but still run the bolt carrier wet. Trust me.

If you have other questions, lets hear them.
 

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Not really but……..When I was in Texas Kenny I had neighbor who was a gun guy and had an AR10. It shot fine…until he put the break on and then it short cycled. The only thing the two of us could come up with was the angle that the gases were taking, (angled backwards to eat recoil) was canceling out what the gas system was trying to do. The gas system is trying to push the BCG back while the break is trying to push the entire rifle forward. He opened up the gas system and nothing changed. We both agreed that a liter buffer spring or a liter BCG may fix it. Downside is I moved back to STL so I don’t what the
outcome was.

I bet if you Google it you’d find something.
I had one a .243 win ar10 i built that had cycling issues, midlength gas, 18" shilen barrel. The gas pressure was way to high and buckled the brass on extraction because it was trying to extract the case before it had time to contract from firing. Bout 12 turns out with the sentry, never had any other issues. But the brass inspection was the key to discovering the issue.

Where the brass ejects at what angle can be a good indicator too.

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OP: as you say, put the 'bad' brake on and see what happens. If it now works, then you almost certainly have your answer as to what caused it. The why would be the next topic for discussion. It is possible that something got broken in or you changed something else in the process of investigating. But that would be pretty remote if brake swap works.

Doctor: "Does it hurt when you do that? ... Then stop doing that".

Part of the DIY build process, right?
 

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Discussion Starter · #9 ·
Thanks for the suggestions. I'm at work so keeping this short right now but will post more later. I do run my BCG wet.
 

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If I read that right, you're using a barrel with a Rifle length gas system and a Carbine action?

That can throw things out of whack to start with.
A Rifle length gas system works best with a Rifle action.
Which is an A2 tube, stock, Rifle length buffer and spring.
 

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Who made the barrel? I’ve heard of instances where the gas port in the barrel was drilled to the wrong size. Off the top of my head, I can’t remember which manufacturer had the problem but that can affect it.
 

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Discussion Starter · #12 ·
OK here's more details:
Ballistic Advantage 18" 5.56 SPR Rifle Length Modern Series Barrel
The gas tube, regardless of how its named, is 14.5 inches long. If you look at my pics below you can see the block is installed in the right spot and extends to the correct spot near the BCG so i don't see how I have the wrong gas tube. After reading your replies above I am wondering if I need a different buffer if I want to run this brake. I can't hit the range to try the brake again until Saturday so I'll report back after that 2nd try on this. Again, fired 100% with the A2 cage Sunday so I know generally my system works.
Thanks for all the info!!
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Rifle length gas on an 18" barrel. That can be testy to tune since the gas pressure is between 12k and 15k. A normal midlength is lets say 18k to 21k, carbine 24k to 26k, pistol being over 30k. So you also have to figure dwell time, or time the bullet passes the gas port, and bullet leaves the muzzle. If to short it wont cycle as with the first dissipators made in the 60's by cutting off the barrel on the m16a1 past the front sight block making it a carbine. The way to correct its short stroking due to no dwell time is by opening the gas port to allow more gas. Then it runs fine.

I have never done an 18" barrel, rifle gas, but i dont forsee dwell time as an issue. I have done 3 16" dissipators with rifle gas systems with no issue. A lighter buffer may solve it, or lighter bcg, like m16 to commercial ar15.

Only way i can see it being the gas tube is if its an enlarged one, bigger than normal diameter, or if the holes arent lining up perfectly. A larger diameter gas tube will lower pressure, sometimes used on pistol length gas systems.

I still do not see it as the muzzle device. Simple thought turn on a garden hose, put your finger over the end, what happens, pressure increases due to limiting flow. I forsee similiar with a muzzle brake in theory.


I think the easiest thing is to try different ammo first. Try some military 193 or 855 and see if that effects it.



Here is one of my 16" dissipators with a rifle length gas, and 5.5oz rifle buffer and spring for example. Runs fine but has an enlarged gas port.

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Also another thought check the bcg's gas key, staking, and gas rings on the bolt. Just as a precaution.
 

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The garden hose analogy isn’t apt - because pressure working in the port and gas system is BEHIND the bullet. By the time the bullet reaches a brake, the dwell time under pressure has been satisfied.

It ain’t the brake.
 

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The garden hose analogy isn’t apt - because pressure working in the port and gas system is BEHIND the bullet. By the time the bullet reaches a brake, the dwell time under pressure has been satisfied.

It ain’t the brake.
possibly, I was thinking more of this disproving the muzzle break as a cause, and how i feel it isn't the culprit in this case.
 
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Discussion Starter · #17 · (Edited)
Eliminate the muzzle brake & see if the problem goes away.
As I stated in my original post, I did that and it did go away. I posted because I suspected, as others here stated, that although the problem went away the muzzle brake should not have caused the problem in the 1st place. I hope to hit the range Saturday armed with a wrench, a giant clamp and padding for the jaws to try both muzzle ends and this time with 4-5 different ammo types to see if I can find a solution to use my brake. Or find out if I unknowingly corrected the gas system somehow when I was examining things after my 1st trip.
 

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Good luck, lets us know what your results are.
 
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Not really but……..When I was in Texas Kenny I had neighbor who was a gun guy and had an AR10. It shot fine…until he put the break on and then it short cycled. The only thing the two of us could come up with was the angle that the gases were taking, (angled backwards to eat recoil) was canceling out what the gas system was trying to do. The gas system is trying to push the BCG back while the break is trying to push the entire rifle forward. He opened up the gas system and nothing changed. We both agreed that a liter buffer spring or a liter BCG may fix it. Downside is I moved back to STL so I don’t what the
outcome was.

I bet if you Google it you’d find something.
I know nothing, but if I am reading your post correctly, it sounds like the brake is in essence "limp wristing" the action?
 

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I know nothing, but if I am reading your post correctly, it sounds like the brake is in essence "limp wristing" the action?
Yes I am. The gas is trying to push the BCG back while the break is pushing the rifle forward, they’re working against each. I don’t claim to know anything either, but I do know this is the second time I’ve encountered this, once in person and here. Both times removing the break fixed the problem. Is the break the sole issue? I don’t know, but the break may be accentuating a gas problem that’s only noticeable when it’s on. I’d try a different break………
 
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