Spring on the bolt stop would be first on my list.
Presuming that the bolt locked back before the new barrel with the magazines being used.
There's nothing about the new barrel that would change the distance the bolt moves back, unless the new port is severely under-gassing the BCG to where it's not going back to where the bolt stop is.
An AR that reliably ejects but doesn't lock back isn't severely under gassed. It's close to being properly gassed. If there are no leaks in the system, the gas port needs to be opened just a slosh to get the carrier to lock back.
Jqcon24, the carrier not locking back is usually indicative of under gassing, with because the gas system is restricted (gas port too small, gas block misaligned, debris in the gas tube), the system has leaks (poorly fitted gas block, gas tube worn where it fits the gas tube, bad gas rings, gas key leaks where it meets carrier, poor bolt tail to carrier fit) or weak ammo.
Another possibility is mechanical. Bolt release binds, bolt release and/or lower out of spec, magazine follower is out of spec, bolt release spring weak/damaged/binding/has debris.
Once I had lock back problems because the mag catch was not adjusted right and wasn't holding the mags in position.
PS- Throw that stupid ejection chart away. It's not reliable for any kind of troubleshooting.
Another thing- Sooner or later you'll need to replace the extractor spring. When you do, use a Colt extractor spring. No o-ring.
Cleaning and lubing the BCG is a good idea, but it won't solve your problem.
