Originally Posted by
kartoffel
Amen to that!
Another thing I think we're overlooking is that The Chart covers carbine length gas, carbine receiver extensions, and 14.5" and 16" barrels ONLY.
For that configuration, the "correct" gas port diameter is 0.062" if I recall correctly. My limited exposure to gas port dimensions and SME's who talk about such things leads me to believe that Colt/BCM/LMT/DD et. al. hover right around 0.062", whereas the shit tier makers sometimes have bigger ports to overcome rough actions and mild .223 ammo.
Now, if you're shopping for an SBR upper, or a midlength, then you're already outside the scope of The Chart. I'd recommend looking for other sources of information, rather than bugging Rob for perceived shortcomings in The Chart.
On the other hand, I think it's pretty dumb to play like gas port diameters are classified info, or a dimension that's not worth knowing. The original purpose of The Chart was more or less to track compliance to the TDP, and I bet you somewhere in that legendary document is a spec for gas port diameter.