I would 1:7 pistol length gas. If you want an AGB Riflespeed, SLR, or Superlative Arms are the best I've found. Like DDadams said if you only plan on shooting supers you probably don't need an AGB.
I haven't used this exact BA barrel, but the price is pretty good.
I haven't used this exact BA barrel, but the price is pretty good.
Ballistic Advantage 16″ .300 Blackout Pistol Length AR 15 Barrel, (Modern Series)
This .300 Blackout chambered 16 inch Modern Series Barrel is machined from 4150 Chrome Moly Vanadium steel with a QPQ Corrosion Resistant Finish and QPQ coated M4 feed ramp extension. Additional Info Length 16
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