The port pop dB's can vary a large degree from AR to AR, even in the same barrel length, by just changing the gas port size. If you take an "overgassed" AR, it doesn't take much suppressing to get the muzzle down below the port noise. On the other hand, if you have an upper than as a longer gas system, a smaller port, and maybe tuned reciprocating parts, you can get away with a much more muzzle-suppressing can, and the maximum of (muzzle noise, port noise) can be a lot less than the overgassed upper, if you do things right. This is not, and was not meant to be, demonstrated in the Summit dataset, but it's easy to demonstrate through metering a few different config uppers with mics at ML and SE.