I use a 11.5 BCM ELW flutted barrel with a Saker-K.
Gas to the face is non-existent with a Geissele ACH. It's overgassed all said and done but with an A5H3 and rifle springco, it's a peach.
I don't shoot it unsuppressed often but it works fine either way and shift is negligible out to 100m. I haven't shot it unsuppressed beyond since the suppressor lives on the rifle.