The issue:
The bolt will not reliably lock back after the last round fire. Sometimes it does some times it stops on the mag follower and not the bolt catch. Sometimes just doesnt stop at all.

The build:
18in SPR ss fluted BA 223 wylde barrel
PSA upper and lower
M&P lower parts kit with G2S trigger
BCM bolt carrier group
upper receiver was lapped
gas block..tried two...wilson combat and an adjustable i think psa

fixes tried:
gas block properly aligned...at least 25 times, adjustable gas block, springco yellow spring, lighter buffer weights, rifle length buffer and spring, carbine buffer and spring, h1 and h2 buffers with carbine spring, blowing out gas tube with air compressor, lots of lube, probably things missing

literally no idea why it does this. it will hiccup on m855 m193 pmc and cheap tula all the same. ejects at about 330/ 4 o'clock

Check the gas key on the carrier. It may be leaking. Use compressed air to blow through it. put some very lite oil in the key to see if it blows out between the two. Ater that you need a set of pin gauges to check the gas port diameter. And try another bcg if you have one. Fastest way to see if it is the bcg

sorry forgot to add, ive tried a smith and wesson and a psa BCG with no improvement. The gas port is .093

Have you tried a different lower to rule out the bolt catch? Sounds like it's running fine with underpowered Tula and full power 5.56 so the issue is probably not gas related. You might need a longer bolt catch or get a 9mm bolt catch and shorten it to fit.

yes i have tried a different lower as well. not sure whats going on..i noticed that on two of the charging handles i have used they have wear marks on them..none of my other ARs have ever had wear marks to bear aluminum. when i first assembled it the bolt seemed to stick. it seems fine now after around 200 rounds but still having the issue

How far past the bolt catch does the bolt go when fully retracted?

1/4in ish maybe slightly more

IIRC, it's supposed to be closer to 3/8".

Can you thread the buffer tube back one turn and it still keep the butter retainer in?

i could try, but that shouldnt matter because ive swapped parts from everything i have to try to make this thing work. It will not work on another lower that functions perfect with the 18ins bolt in the 16in upper

If you have a bad lever on it, you'll have to cut the bolt catch spring a small amount to reduce the effort and speed required to get the catch to pop up.

negative on the bad lever

Have you tried with different mags?

Otherwise.. does that same lower work 100% with a different upper?

System sounds underpowered. Check gas block alignment, gas path for obstructions, and excessive gas leakage from manifold.. Check for hangups causing mistimed function; barrel extension lugs or bolt lugs for peening or undo wear.

Did you pin gauge the gas port or are you relying on mfg spec?

18in SPR ss fluted BA 223 wylde barrel

This is likely your problem. I had a nitride mk12 profile 18" rifle length from BA and the gas port was sized the same as a 20" rifle length, i.e. too small. Around .09 IIRC. Proper size for an 18" rifle length is somewhere around .10-.105".

I bought a good drill bit from McMaster and carefully enlarged the port on a drill press. It resolved all my problems and did not negatively effect accuracy. Prior to this it was short stroking similar to what you described. After enlarging the port it would cycle underpowered wolf steel case in the cold with no issues.

The original version of the MK12 SPR, with an 18" barrel with a rifle length gas system, calls for a gas port diameter of 0.0995".

There may have been some changes since the original specs, but that was for functioning with MK262 and M855 ammunition at the time.

For reference, 0.093" is the gas port size for a standard 20" A2 barrel.

i have tried several different mags including several pmags, gi mags with magpul followers, regular gi mags from like 2004, and troy mags. all do the same thing. I used a drill bit gauge to measure the hole

.093 hole, I would open it up to ~.100.

Maybe try an undersize drill first and measure the resulting hole.

If you decide to drill it out. Put a cleaning rod in the barrel so you dont drill into the other side.

I do the same.

I use a metal cleaning rod, loose inside the barrel.

As soon as the drill contacts it, it dances and rattles around, making enough noise for me to stop drilling right away.

A small, "drill stop" (or masking tape) attached to the drill is the an even safer way.

so open the gas port hole up to .100ish?

"Anything will work with a big enough gas port."  The problem is that tens of thousands of those barrels are out there functioning perfectly fine.
Is this a new build, or a rifle that ran fine and now doesn't?

Maybe try 0.095", especially in drill size, as the resultant hole will be larger than the drill.

A #88 drill is 0.095" and a #87 drill is 0.100".

A #89 drill should be 0.091".

Drilling your gas port should be the absolute last resort.  These guys on here are so obsessed with gassing it's ridiculous.  First, they'll tell you to hog it out.  Then they'll tell you you need an adjustable block.  Then, ten guys will say adjustables suck and you should use a BRT gas tube.  It very well may be a bad port, but those barrels are very popular and I've never really heard anything about improper cycling except from Tula bros.  If it is to the manufacturers spec, you shouldn't need to drill it.  If it isn't to spec, and it's new, call BA, and they'll replace it.  Or if you want, accept the risk of jacking up the barrel, and then it's modified with a voided warranty.  If it doesn't fix the issue you'll be out the barrel, and still have the same problem.

I had a similar issue when breaking in a new build.  I started checking all the normal failure points but was perplexed, because when manually operating the action it would always lock back on the catch.  I had plenty of gas flowing for it to function properly, but it would only lock back about 1/3 of the time.  I hit everything with the air compressor, wiped it down, and then realized I never lubed my fucking bolt catch.  It was a snug fit in the receiver too.  Two drops of oil, and about 5 minutes of working it burnished the fit.  I blew it out and reoiled.  I haven't had an issue with it since.  Check the simple stuff.

Post an image link of that unusual charging handle wear.  The bolt sticking when first assembled is also an indicator of improper assembly, or out of spec parts.  You probably should look for odd wear inside the receiver and lead into the receiver extension.
You mentioned that the receiver was lapped.  How was this done?  Did you sight in irons on this build?  Did you need excessive windage or elevation adjustments to zero the rifle?

Guys, this isn't rocket science. There is a spec for gas port size established by crane (.995") and BA isn't using it for some reason. Search around and you can probably find a dozen threads on various forums of people reporting the same issue.

I'm sure there is some combo of perfectly efficient gas block and gas rings that will allow this to cycle with full power ammo, but without hand selecting and measuring parts to achieve that, many people report issues with these BA barrels. A suppressor would probably also help with cycling, maybe that's what BA had in mind. FWIW I am not a proponent of adjustable gas systems.

My suggestion: buy a quality cobalt or TiN .100" drill bit from McMaster. Use that as a gauge. If it doesn't fit, drill bit out, and enjoy your functioning barrel with a now properly speced gas port.

There's already a hole there.

A larger drill is just to open it up a bit.

It shouldn't take much of a drill to do that.

The gas block journal of the barrel should be clamped 90 degrees to the drill, so as not to angle the gas port.

Besides straightness, the other concern will be not drilling too deeply in the barrel.

If a drill press, instead of a mill, is used, the drill is very likely to have some wobble, so maybe try a slightly undersized drill, as the resulting hole will likely be slightly larger than the drill used.

The existing gas port in the barrel should guide the drill fairly well straight.

Maybe a metric drill will be sized between numbered drill sizes.

2.5mm is 0.0984", so I would get a couple of 2.5mm drills, of any decent steel, if super hard ones can't be found.

I would attach images but idk how. The wear on the charging handle is on the top left side. It has worn through the finish on 2 charging handles