Aero recievers
Aero nitride bcg
Ballistic advantage barrel
all other parts are from BA kit

Head space checked with Forster go/no go

Ill try to summarize and not make this long as hell, but it still will be

First trip to the range... after assembly I started off with only one round loaded in magazines so I could set the adjustable gas block.  I chambered each round using the release from bolt locked back.  1st round chambered, fired, ejected not very far and bolt did not lock back, as expected, the gas block was nearly closed.  I opened that shit 1/2 turn and repeated.  Better ejection, now, still no lock back.  3 rd attempt after another 1/2 turn more open on the gas block, bolt did not fully close, had to bump the FA, then fired with good ejection to 3 o'clock and bolt locked back.   I left the gas block here and tried the same again with 3 different magpul mags, each with one round.  All of these had to be seated using the FA for the last 1/8" of bolt closure.  All fired and ejected well.

I then went with 3 rounds in each of a mag, attempted chambering by slingshot with charging handle fully back, first round did not fully seat and required FA.   The second and third rounds in mag also required FA to seat.  At this point I stripped the bcg to clean and lube.  The bolt did not move as freely as I would like in the carrier,  after cleaning the gas rings and the inside of the carrier and re-lubing, it seemed good to go.   So back to 3 round in the mag.   I slingshot that bitch and the round chambered fully, I think to myself, ok, so its dirty, needs to be broken in, whatever.... first and second shot chambers and fires and ejects properly but 3rd again had to use the FA to seat.    The rest of this range visit I played with more or less gas, but this did not change the chambering issue.

Since then I have read every similar post of this issue and checked everything.
I have thoroughly cleaned the chamber and barrel extension, as well as the bolt, gas rings, and inside of the carrier.   I disassembled the bolt and found 2 o rings and on the extractor, I removed one, even both at one point.   I ensured the gas tube is not dragging on the gas key.   I checked barrel seating and alignment in the receiver.  I checked gas block over gas port even though this is clearly not a gas issue.

2nd range trip.....    After removing the one ( and temporarily both) extractor o rings, the chambering issue is the same.    The rifle seems to function ok when freshly cleaned and lubed,  but quickly deteriorates.   The ammo?   to this point I  have been using only Prvi Partizan 7.62x51 NATO 145 Grain.

More interweb reading and I spend more time on the bolt, I took down some sharp edges on the extractor, and I worked the bolt lugs to the receiver extension with lapping compound.

With no round and everything freshly cleaned and lubed, the bolt closes smoothly,  even if only pulling the CH back enough to see the bolt face through the port.   Before this, when it was dirty- if 30 rounds is enough to make it dirty- the empty gun still felt a lot of resistance to fully close the bolt.

3rd range trip.....  tried some Winchester NATO 147 grain and some Federal 308 150 grain.    I ran 5 of each back and fourth,   the first failure of the day was on the 12th round, then every round there after.  Same failure to fully chamber.

I did a clean and lube, the bolt to carrier fit was tight, barely moving.   After cleaning and lubing it works smooth.   Loaded up some the the Pravi,  now 15 rounds run ok before the same failure comes back...

enlighten me

It's not dirty, it just needs to break in a bit more.  New builds always need a little break-in.

Get some inexpensive 308 factory ammo, load up a couple full mags, and shoot at something like a 200-yard steel (not worried about super precision, just hits) and run thru it as quick as you can stay on target, get it good and warm.

And lube the crap out of the BCG before you do it.

I dont know, sounds like something is way too tight. When heated, it swells just a cunt hair or two, which starts to lock shit up.

After the description, Id suspect out of spec gas rings. But, its hard for me because there are so many issues to diagnose with Aero's design, could be just one, or combination of many. Plus, I still have a really bad taste from my own experiences. Kinda hard to stay unbiased.

It does seem like the rings are stupid tight innthe carrier.

You know the thing you can do with the BCG (out of the gun) when you push the bolt into the carrier and then holding the end of the carrier you whip or flick the wrist and the bolt should rotate and move forward?

This BCG will do as described after a clean and lube, but after 20 rounds fired, no way.  Not happening.

I'll bet it's an issue with your ejector.   Knock out the roll pin and remove it .   Polish it with some flitz and clean out the channel.   There are videos on YouTube about this.   Worse case get a new bolt.

I had one that was giving me issues similar to yours.  It definitely needed to be broken in.

After reading all the steps you've taken, I have one you may not have considered.

The inside of my buffer tube had these very small ribs on the inside of the tube.  (It looked sort of like a ribbed prophylactic)  Because it was dry in there (no lube) the buffer spring was catching on the ribs a bit, and it affected the cycling of the action.  There's a weep hole on the back of the stock, so I put some MPro7 in there, cycled the action a bunch of times, and it solved the problem.  The action was still stiff, but it functioned.

Just thought I'd pass it along.

You could try a heavier spring.

I did disassemble and clean the ejector as part of the bolt cleaning.

A new buffer spring is worth trying, and I'll just continue to break it in.

Thanks

Had problems like that with a 5.45 build. Ended up putting a chamber brush in my drill and 'polishing' the chamber for a few minutes. Worked wonders.

I run a geisslie super buffer kit in my ar. It’s a  Braided spring that’s stiff as all get out and comes with its own buffer that you can add tungsten or steel too add weight.

This is the gas block

The spent brass looks fine, no marks like in your photo.  Nothing funny from the extractor either.

Maybe it just needs more gas?

If this was my rifle, I'd disassemble the upper, and the bolt.  I would then check fitment of bolt and chamber, with and without a live round.

I imagine that it would be fine and tight, and somewhat inconclusive to a specific problem..   At which point I would proceed to doing Hellbenders fluff and buff on most all of the parts...

https://www.ar15.com/forums/Precision-Rifles/Hellbenders-guides-to-Ultimate-AR15-and-or-AR10/4-42/

Or you could hand cycle the action a couple hundred times after oiling it wet, especially the charging handle sides.

Everything you ever wanted to know about chamber polishing,,, see table 1

https://www.varmintal.com/a243z.htm

On the first range trip I tried with the gas block fully open.

I have done this since the second range trip.  It does cycle (by hand, w/o ammo) smother with lube here.

I did a complete disassemble and re-checked things like this.   The gas block is a C-hair off of the shoulder in order to completely line up with the port.   I carefully measured before setting the gas block in place.

I fairly sure it is not a gas issue.

This thing may have run from the beginning with a heavier buffer spring.  I have ordered a springco 'orange'.
I am not one to say or believe "use a heavier spring" is the answer to any gun problem question.... but it may solve this one.

Since my last post I have scrubbed the chamber with a new brush in a drill, thoroughly cleaned and dried, then polished with a cotton mop and metal polish, and cleaned and dried again.  I have a couple different kinds of ammo on order to test.

This.

A brand new chamber, even one in spec dimensions, can sometimes grab cases like this.

I usually wrap some 1000 grit paper on a brush and then follow it up with some polishing compound.

Have unfucked a good number of mystery problem rifles like this.

Keep it wet.

Got the same issue on an Armalite AR-10T. Up till now I've blamed it on the suppressor. I have an SLR adj gas block on it. But the chamber fouls so bad after 10-20 rounds, that it has to be cleaned. It probably has 1000 rounds down the tube from the previous owner so it's not a break in issue. I just replaced the buffer spring and haven't made it out to shoot it again. It still may be a suppressor issue at this point. I did check and verify the weight of the buffer.  Curious to hear how yours does with the new spring as well.

It js called the action spring.

Yeah, OP, maybe you need a stronger spring &/or a buffer w heavier weights inside to give it that extra little bump into battery?

I would remove lower half, extractor and ejector turn the upper hald upside down, drop a rd. In and slowly chamber by sliding the carrier manually  so yoy can geel exactly how tight it is.

Also, after you chamver a round, remove the carrier leaving the rd in there.  When you tilt the muzzle up the cartridge should fall right back out of the chamber.  If it doesnt it may indicate that your chamber is too tight or rough

Had one doing similar things.

Ended up being the magazine spring was very robust, dragging down the inertia of the BCG flying forward.

Tweaked the spring a bit and problem solved.

Heavier buffer spring would probably work too. Look at the Tubb flatwire ones Brownells carries.

Shot mine today. New 20% heavier Spring made no difference. 7 rounds down range then it ceased to chamber. Had to smack the butt on the bench to eject the round. Tried to chamber two more, same result. All rounds were fired thru a Sig 7.62QDTi can. 20" or 22" barrel, can't recall at the moment.

Update from the range

I just fired 40 rounds of the same ammo without a single malfunction.  This is after scrubbing / polishing the chamber as described above, very generous lubrication, and with the new springco orange action spring.

Went back to the original spring that came in the kit, the rifle does now cycle with it, but the recoil impulse feels? better with the springco...

I then tried some other various ammo that I picked up, all ran 100%

ETA
When trying to extract a live round everything still seems very tight. I didn't have to do a full mortar but I bumped the stock on my hip while pulling the charging handle in order to get the bolt to open

Glad to hear everything is looking on the up and up OP.

I had this issue when my 308 AR i built a few years back.  I would be lucky if i got 10 rounds before it would FTF or FTE and usually cause the BCG to go about 95% into battery but never go all the way.  Checked everything, cleaned the snot out of it, ect.  STILL did it.  While trying to figure out the issue someone said to check the *clean* chamber with my brass/round *since i reload* and see if the round basically "fits" in there correctly or if it gets stuck.   Well, with a clean chamber and a new round made, the round would get stuck and you would see it actually didnt chamber all the way.  Come to find out, my JP barrel was more towards the SAAMI min spec and the dillon case gauge was more towards the max.  I ordered a JP case gauge, found out all my reloads were WAY out of spec (for the JP).  I ended up getting a 308 AR small base die, resizing them all to the JP case gauge and they all fit the barrel perfectly *basically slide in and out of the chamber.*  4 years and about 500 rounds later, not 1 issue since.

When you use the charging handle, do you feel like it starts to bind? Check your can pin and the area the can pin tends to hit the upper

Same with my MATEN and Rainier Match barrel.  Chamber is toight like a toiger.  Just pulled down 45 rounds this past weekend where the brass was SLIGHTLY (like 2-3 thousandths) longer than max length, and headspace was well within SAAMI spec but on the "long" side of it, and they wouldn't chamber.  Got them resized with a small base, trimmed to 3 thou under book "trim length", recharged/bullets seated, and heading back out Sunday to (hopefully) get some shooting done.  

Same mags!

So I built two rifles that are nearly identical... The one I built for my father had a full weight BCG and didn't exhibit that issue. Mine has a Ti carrier and had the problems.

Less inertial energy... Blah blah.

Same barrel, same ammo, same buffer spring and buffer - it confused me for a minute.

No......it’s not

Well, it's called an operating spring for Armalite. Same spring for carbine and rifle. So yeah...