I've shot it with weaker brass cased 223, but not steel. If you want to shoot steel cased ammo, you're going to want a barrel with normal or slightly overgassed port. It's the only way to ensure reliability with weak or inconsistent ammo.
I'm running a 5.56 can, but I beleive Righter13 is running a 30 Cal.
I'm running a standard gas block, gas tube and an LMT enhanced carrier. My goal was no adjustment necessary. However, a member on m4carbine.net has been using his with an adjustable block and a heavier carrier than me. That tells me that the reduced port still has some cushion and isn't so tight that it is running on the ragged edge of reliability.
I've spent a good bit of time discussing this barrel with Sionics in real life. The barrel was originally designed for a specific Police Department SWAT Team. Sionics tested it for months to ensure that it would run unsuppressed with PMC bronze, even though the PD specifically stated it would be used with suppressors only. But Sionics wanted to design in some cushion because they weren't comfortable taking the risk that it could be used without a suppressor. They wanted the gun to run no matter what, because dead officers isn't something you want on your conscience. It will run unsuppressed, but steel case ammo could be iffy in the reliability department. It would probably run suppressed though. I'll have to test it next time I get out to shoot.
They just had another run available about a week ago, but they sell out quickly. Probably have more in 8-10 weeks.