I was planning on running a 8" with a can, if I decide to get into the 300 blackout.
I am working on a 300 Blackout build myself. TBAC can but 10.5 inch barrel. Most 300 bullets fully burn off the powder by 9" [little to no flash] and at 10.5 there will be less beating my can up with the pressures while still having a rather short setup.
My life working is only preparation for my life as a hermit.