I've searched and searched and youtubed and trouble-shot (trouble-shooted?) and can't find my exact issue/solve.  So, here's yet another gas problem thread:

New AR build
20" barrel
Rifle gas system
Carbine buffer/buffer tube/spring
Gas key tight and staked

Originally, I had a Trinity Force gas block.  The carbon ring was showing lined up well horizontally (thanks to the barrel manufacturer's dimple), but it appeared that it may not have been lining up vertically (not far enough down the barrel, even though it was butted against gas block shoulder).  I returned it and got a YHM gas block, thinking the TF gas port might be out of spec.  Installed YHM today and exact same gas issues.

Brass ejecting approximately 5 o'clock
Empty mag test fail (but it locks back on empty mag when manually racked)
FTFs and FTEs on .223 ammo after about 2-3.
FTFs on 5.56 ammo after 3.

Not to sound like a smart ass but is your bcg lubed?? On new builds I soak mine till everything gets wore in.

No worries.  All questions/suggestions welcome, in case I overlooked something.  Yes, it's nicely lubed.  Passes the 45 degree test without a problem.  There doesn't seem to be any hangups or friction problems.

Sounds like it may not be a gas issue. Is your extractor spring tight? You may need a better spring and O ring but you will not be able to tell visually. I had a tight chamber before and would have similar problems until I bought a BCM spring and O ring. It fixed the problem.

That would cause a failure of the empty mag test?  It seems to extract fine.  When I mentioned FTEs and FTFs, it is almost entirely FTFs.  When it FTFs, it's almost like the bolt tries to close on the case before it's in the chamber.  I have some pretty deep grooves in the bullet casings as the bolt tried to close on it before it was ready and the bullet seated diagonally when the bolt rammed into it.

Gas blocks aren't meant to be butted up against the shoulder. If you're old enough to remember classic mil-spec handguards, there is a cap that used to go between the gas block and that shoulder to hold the front end of the handguards. Gas blocks and barrels are still cut to the proper spec to leave room for this handguard cap - unless specified otherwise.

If your barrel is dimpled, and you use a set screw to center into this dimple, that space should set itself properly. Otherwise, you can buy a spacer/shim from quite a few sources, or make your own using 22ga sheet steel.

EDIT: The space should be .03" which may not seem like much, until you realize that gas ports are as small as .06 and top out around .12 or so. .03 can be enough to block as much as half of the barrel's gas port.

This.  You don't mount a gas block against the shoulder.  Use a shim or space it about the thickness of a thumbnail off the shoulder.  Then you'll be aligned.

This is a moot point, as when the gas block is butted against the shoulder, the ports STILL did not align, as the gas port was still too far forward in the replaced gas block.  In other words, with the gas block butted against the gas block shoulder, the port was still not far enough towards the rear of the rifle to fully cover the barrel's gas port.  It's also moot, as I've replaced that TF gas block with a YHM gas block and it gives the same issues.  Also, the YHM gas block is so tight on the barrel, when I removed it it ruined any type of carbon ring on the barrel.  I'll try again later today.

but there is some leeway there, as the gas block and gas tube openings are much larger than the gas port itself, I take a measurement with dial calipers to make sure Im good.......

Yes, but at the very least, the gas port on the gas block should entirely cover the much smaller gas port on the barrel.