I needed to include my calibers as 7.62x39 and 308, only running x39 with subs and supers and 308 supers only. Gas port sizing needs to meet a minimum diameter to supply gas on carbine length gas system to reliably run subsonic suppressed and that's where adjustable gas block comes into play. All my x39 guns have same size gas port and tuned to run subsonic whether 8" sbr or 16" rilfe running brown bear 196 grain or hornady 255 sub-x line. 300 blk and x39 very close when it comes to tuning I have found especially when x39 subsonic Ammo now available. I do own factory x39 guns such as pws in all lengths that run subs 100% also, even my custom ak's have definitive arms adjustable gas blocks on them to keep them running subs and supers flawlessly and I do believe a finely tuned gun will last a lot longer.
