Sionics Reduced Gas Port 11.5 bbl.
I was looking for an 11.5" barrel that would run well suppressed, something with a properly sized gas port. The disclaimer from Sionics is that it may be undergassed when unsuppressed, and may therefore cause malfunctions without a suppressor due to the smaller gas port. (It measures right around .070") Since I don't have my suppressor yet, I figured I'd test it out unsuppressed. I shot several types of ammo, using both an H1 and H2 buffer, and never had an issue. Even when using some weaker 55gr .223 ammo and an H2 buffer the ejection pattern was still within the "properly gassed" range.