In my never ending quest to get weird configuration barrels made I stumbled upon these guys.
They've got tons of options and their FB page makes it look like they're not afraid to make some odd things and work with you on custom contours and port locations. I just can't find much in the way of hands on reviews.
Precision barrels | 8.6 Blackout
Precision barrels. AR15 Barrels Stainless. 8.6 Blackout. We also provide precision rifle barrels, quality firearms barrels, and
mos-tek.com