i want to know, from you guys in the know about 300 blackout, why the uppers PSA has for sale are using the pistol gas length, even the 16 and 18 inch bbl.
Because 300blk's pressure drops very quickly and pistol length gas is the most reliable for using both subsonic and supersonic loadings.
You can also use those barrels to make a shorty upper because pistol gas is needed for anything under 16" to cycle reliably.