This is all good to hear.  I was a little worried.

I just did my first range session with the new STG-556.  My dad gave me 250 roungs of the 55gr Wolf for my birthday and mine It no-likee, either.  Even on the "high" gas setting, it would eject fine, but the bolt/carrier wouldn't cycle far enough to strip a new round out of the magazine.  Thankfully it was a zeroing-in day... and the range I was at (Kenmore, Seattle) was finicky about loading one round at a time, anyway... so no big loss.

I did run 30 rounds of Federal 55gr practice ammo through (I think it's a laquered steel case, too) and then 30 rounds of Federal duty hollow-points through it, too.  Divided it between all my 30r mags (to make sure they all work, too).  The Fedeal stuff fired and functioned just fine, even on the "low" gas setting and all my mags worked as intended.  I'm still happy to hear it'll "break-in" a bit.  I've still got a bunch of Wolf left over!

I still got a little ways to go for zeroing in.  I had a respectable fist-sized 50 round group at 100 yards... just about the 4:30 postion about 4-inches from the bullseye.  Had to stop, though.  My eyes were getting a little tired and buggy in the twilight hours.  I think one more slow-speed sit-down session and I'll be good-to-go.

Definately another happy customer so far.

Initially, I started braking in my STG with XM193 and SS109. After about 100 rounds without malfunction I then decided to try Brown Bear 62gr SP, and experienced the same FTF mentioned issues. Subsequently, I returned to firing  several hundred further rounds of SS109, again without failure. At present, now thoroughly broken in, the STG digests BB SP on the normal gas setting without qualm.