So, SEVERAL years ago (like when Justin opened Texian years ago) I started getting all my parts and I finally FINALLY had time to finish my build.....2 years ago.

Today I decided to take it out to the field and zero the scope and adjust my gas block.

Well, the rifle shoots like a champ. SOB weighs in at 12 lbs so no issues with recoil or staying on target. LOL.

I have an ERGO .750 Low Profile adjustable gas block. BCG is Aero nickel boron BCG.

I followed the directions.

Screwed it all the way in, bolt barely popped open at all. Fine. That's what it's supposed to do. Then I turned out the screw 1 full turn. Every turn, the bolt opened more and eventually it got close to stovepiping, then every 2-3 rounds would actually eject. SWEET!....But the bolt still not locking open...so we press on!

It was when my adjustment screw fell out onto the table that I realized I wasn't going to get an adjustment that would make it work.

Now, I don't know what to do. I dimpled this barrel with a KAK jig. Impossible to screw up and I was very careful about making sure the alignment screw was in the port. Everything there was lined up. Everything LOOKS in order.

But I don't know where to go from here.

What do I do next?

I feel kinda bad because I sort of thought this couldn't be screwed up and I took great pains to ensure everything should work together with standard tuning processes.

Barrel is 18"....I don't even remember who makes it. I bought it from Texian years ago in anticipation of a build. I want to say Ballistic Advantage but I don't know. There aren't any markings on it.

How do i troubleshoot it? It seems pretty simple...it ain't getting enough gas...but I don't know how to remedy that since my adjustable gas block is out of adjustments. HAHAH...

Ammo I was shooting was Winchester 7.62x51 149 grain, 2790fps M80 FMJ.

Adjustable gas blocks are great when they work. I don't really trust them. I had one on a PSA AR-10 in 308, also 18" barrel. It worked for a while, but not consistently and I did have to back out the screw to have a reliable rifle in the end. To me reliability matters most, so maybe a standard gb.

Should be a ballistic advantage barrel if it is through us, hard to say after this time, though.

BA did have a run of time when their had ports were a bit undersized. Generally worked but we definitely had to open quite a few up a few thousandths.

Not exactly what I'm going to recommend you doing unless you feel comfortable with that, and even then you need to measure and check first

I feel bad asking, but did you lube it well first? Ar10s like to be wetter than.... Ar15s.

The ballistic advantage marking is a spade, btw

TheEyeGuy said:

---

Should be a ballistic advantage barrel if it is through us, hard to say after this time, though.

BA did have a run of time when their had ports were a bit undersized. Generally worked but we definitely had to open quite a few up a few thousandths.

Not exactly what I'm going to recommend you doing unless you feel comfortable with that, and even then you need to measure and check first

I feel bad asking, but did you lube it well first? Ar10s like to be wetter than.... Ar15s.

---

It arrived from you July 2021. Pretty sure its BA. I don't see any spade markings, but they could be covered up somewhere.

What should the port size be on the barrel? I can probably figure out its size once I get the block off to know if it needs to be bigger. Seems easy enough to measure.

I did lube it with some light grease, but it's not wet by any stretch.

I feel like we got close with having it fully eject a casing or two, but not quite there.

Don't feel bad for asking anything. I get focused on stupid things sometimes and don't do obvious sometimes.

Is this not something a different buffer weight would help?

Lol it's just one of those simple things that some don't realize. Especially on ar10s... I know people that run Royal purple on them as lube

The markings for ba are on the top of the barrel and probably covered by the gas tube

Buffer weight is definitely something that can be adjusted. You can get a heavier/lighter one then switch out weights between them to adjust further

Try 308 win, it's higher pressure than 7.62x51.

When I was building ARs, I had a box with 4 different buffer weights and two different strength sprinco springs that I would bring to the range. Test and tune.

Agree with all of the above.

Buffer weights, springs, and lube it like it is at a Diddy party.

Mine settled in after a couple of boxes. If that doesn't work I would try another gas block.

Yeah, I know you can drill the port and online it seems like that is the first 'go to'. I have no problem with that, but I don't feel like it might be necessary. I'd rather tune it as it is before taking that extreme measure.

Any guesses which springs and buffers I should try or get to tune? I have the Aero Rifle Length Buffer kit in it now. I don't know what spring it is but they say the buffer itself is 5.6oz.

My goal is to 'shoot whatever I want' out of it. I'll probably hunt with a proper hunting round, but it would be nice to shoot the cheap Winchester 149 grain for grins. I am pretty sure a proper hunting round will cycle fine but I haven't tested that yet.

Ready for the Diddy Party.

TheEyeGuy said:

---

The ballistic advantage marking is a spade, btw

---

Duh....it's exactly where you said it was. Under the tube. I couldn't see it in the dark and with my now less than stella close up vision.

BA .308 WIN 1/10 4150 CrMoV U11325

If you are confident that your gas block and tube are installed correctly then I would look at your buffer weight and spring. There are some calculators or tables on line that can provide a recommendation so you aren't just buying a bunch of pieces and swapping them blindly

I THINK I FOUND THE ISSUE???


I don't know how to fix it though. I used the KAK dimpling jig so this wouldn't get screwed up. It looks like the damn block needs to go toward the receiver a bit. However, the block is already aligned with the dimple I drilled and it turns out it is also already against the barrel shoulder. I can't really move it any further that way. LOL.

It's like the barrel port is off or the block port is off.

So ugh...now what the heck do I do? O_o




You can see the dimple in the set screw hole. It looks like it is where it is supposed to be.



ERGO Manufacturing error or simply not compatible with my BA barrel?

As most of us are not shooting tons of ammo I find the nickel boron to be pricey for not a lot of improvement. Some say they stay slicker but I have found that they don't and it is a part that has to be wet! Just a pain jane BCG of good quality is all you need. Do take it apart and get to your gas rings and make sure you have no gaps. I bet that is the issue since it was NOT cycling great for a while then not. Bad cycling from the get go would make me think gas rings have a gap.

Well looks like you solved it.

Put it on a sander and see if you can take some material off and get a little wiggle room to line up.

What am I missing? While not centered, it looks like the barrel port is fully covered by the hole in the gas block. Just judging by the oil on the barrel in the area.

I find the Ni Boron parts to be slick as heck and wipe clean easily-- a huge improvement in my opinion.

The step up on the BA barrels isn't a straight up 90 degree turn. You might be able to remove a bit of the inside of the rear of the gas block all the way around and get just enough to seat it a hair further back.

Otherwise, I have a feeling it's a tolerance issue. Both companies are decent to good, so while it could be something made out of spec on the gas block (not likely but possible) it could also be the gas port was drilled off (not likely, but possible... I did have a barrel from BA come in without rifling so they aren't perfect). I have a feeling it may be more of they generally work under most circumstances but if you get two extremes of tolerance, they stop jiving as there is no "mil spec" on AR10s.

The more that I look at that pic, the more I want to say that port might be drilled a bit far back.... But pics are deceiving.

TheEyeGuy said:

---

The more that I look at that pic, the more I want to say that port might be drilled a bit far back.... But pics are deceiving.

---

Should BA be able to give me the exact spec of where it should be so I can determine that and have them fix it if needed?

Center of port hole to barrel shoulder is right at .250 inches

I'm also of the understanding the barrel shoulder should NOT be tapered or chamfered like it appears.


The base of the chamfer puts the center of my hole at the.250 but at the top of that chamfer it puts the hole at .270 which I understand is what it should be. .270 is wha the gas block center to shoulder is.

Edit to add…none of this should matter since the JIG I used based the dimple off the port location in the barrel. So, if that relationship is right and the dimple lines up with the screw hole, then it must be the gas block port that is mis drilled.

I might try a Superlative Arms block and see if that works right. Not sure. Very very interesting.

Just drill out the gas block. If it doesnt work, it is the cheapest and easiest to replace. Also, there is no guarantee that another gas block with align correctly either. Just drill it out, but go slow and insure the new hole is concentric and not wallered out.

I save my large rifle primer cartridges for bolt actions. Never been able to get good follow up shots on pigs with the AR-10s

Wait, did you get that gas block from me way back when, as well?

Yes. I got the barrel, the ERGO AGB, Gas tube, and lancer nitrous compensator. I've been quite happy with all of them.

Barrel port size will fit a 5/64 bit in it with a little slop so it's got to be at least .080".

I have not truly determined if the barrel or the block is the actual issue.

I took everything apart and put my KAK INDUSTRIES JIG back on the barrel and looked through the holes. Everything is perfectly centered in the set screw side, which means the dimple I drilled is right on the money. And since the gas block sits flat against the rifle shoulder and the DIMPLE i drilled lines up perfect with the hole for the set screw, then that can ONLY mean the misalignment of the two ports is on the Gas Block Side. Could be stacking of tolerances. Hard for me to tell or get my gauges in there to measure.

Years ago, there was a recall on the ergo gas blocks. What the problem was, I don't remember.

OK. Screw pins and guessing and spaghetti noodles thrown in the gas port for alignment.

I went full ....bore...if you will.

Two pics.

First here is one of what it looks like when the gas block is not aligned.

Also gas port size in this barrel is .085"...verified with pin gauges.




Second one is where mine sits with the screws set in the dimples. I do NOT know why the burn marks look different, but I think it is safe to say this port and block are aligned.





By the way, You can essentially move +/- half a dimple and still be pretty close.

So, I guess it's back to the drawing board to either look at opening the port or springs and buffers.

I may throw this all together and oil the **** out of it and shoot another box and see if anything improves or if there was something that just wasn't right the first time. Maybe this is like a USB plug where you have to rotate it 180 degrees 5 times before it finally goes right.

Barrel Port is where it should be and has a size of .085" verified with actual pin gauges.

Good plan. I would still be curious if it reliably shoots 308.

also check the fasteners at the top of your bolt carrier to make sure they are tight and not leaking gas. Check the gas rings on the bolt. Look in the upper receiver and inside the buffer tube for unusual drag marks.

CactusThomas said:

---

Good plan. I would still be curious if it reliably shoots 308.

also check the fasteners at the top of your bolt carrier to make sure they are tight and not leaking gas. Check the gas rings on the bolt. Look in the upper receiver and inside the buffer tube for unusual drag marks.

---

Good idea! I did check gas rings. They check out. I checked the brass for claw marks and gouges indicating chamber burrs or extraction/dwell issues. Those look OK.

Ill check the top of the block and buffer tube...

I don't really know how to test the gas key. I sprayed some light oil around the gas key and put 5psi in the hole and get a lot of bubbles under the gas key in the front. I don't know how much is too much but with the bolt pushed in,it still readily pushes back out with a tiny bump of air.

How do you know what is good and not? I have two brand new FailZero botl carriers as well, still in the package that leak in the same place even more, so I don't know how much this test really tells me. I read about these 'leaks' and this isn't a precision milled mating surface like a cylinder head, and there is not a gasket so.....of course it's going to leak air there. So, I don't understand the purpose of these tests.



Here is the other BCG I have...brand new...tested directly out of the package.



Same thing. So is this really a big deal? Aero precision says NO, it shouldn't leak even a little and we'll send you new ones until it doesn't. LOL.

Arent we talking about 30,000 PSI up in this thing? Should I really be worried about this? Serious question, this is all warranted so, whatever.

I can take the key off and lap it and apply some permatex no 3 aviation if they manufacturer won't freak out.

My gut feel is the gas keys are fine. That is an interesting test. I've never seen that before. The time I've fixed a gun with a problem there, the fasteners were very loose.

Not saying it isn't possible, but I haven't seen a fail zero gas key be jacked from the factory.

More likely would be adjusting buffer weight.

TheEyeGuy said:

---

Not saying it isn't possible, but I haven't seen a fail zero gas key be jacked from the factory.

More likely would be adjusting buffer weight.

---

So the leak in the failzero is non critical is what you're saying.

That is also my opinion.

Buffer weight is the next place I'm going. But I don't know where to start. I have an aero buffer kit and it's 5.6oz according to their online specs.

By the way, I'm throughly enjoying the troubleshooting process and have learned more about these systems in two days than I've known.

What buffer should I purchase to make that change?

I think you mentioned you are using a rifle length tube? Back (a long time ago) when I was doing these things there was only two commonly available buffer weights for the rifle length. Hopefully that has changed.

Some buffers have a pin you can take out to disassemble and remove some weight.

I have used this calculator to try and figure out what buffer i need for an AR-15. They have the option to select AR-10 as well. Might be helpful to you.
JP - Buffer Springs and Silent Captured Springs https://share.google/clGdkhzOuwIE806pb

Thanks for the calculator!