I have never seen, nor heard of a mid length 300 blackout barrel. The blackout is optimized with a pistol or carbine gas port. Some 16" barrels with a carbine gas port will not cycle subs reliably, others will work fine. With pistol gas, both subs and supersonics should cycle fine with or without a suppressor.
I'm sorry I hurt your feelings when I called you stupid. I thought you already knew.