To me, this is also the hardest path and akin to direct milling your pistol for a specific optic footprint. The EZ tune is as reliable IMHO, good for 10k rounds, and can be swapped out in 15 minutes. I am getting 2 pistols direct milled but when I think about a custom barrel, I am too cheap to pay full price!
I shot my 12.5 Carbine gasser today with the .057 EZ Tune (which is stated to mimic a 0.055 gas port). It worked 100% as expected with my suppressor and rifle spring+A5H3 buffer (I was too lazy last night to break open the buffer to make an A5H2***). One one hand, a smaller port is possible if only shooting 5.56 ammo, but even with the AGB I would find the correct setting for 223 lockback and then open it up one more click for the homies who aren't with us. That was doubly conservative for shooting 5.56 and I wonder if that is the equivalent to a 0.055 gas port?
No issues today with 5.56 55gr, 5.56 77gr OTM Clone (my precious stash of CBC), and some cheap BVAC .223 55gr that is probably my lightest load. But not a stress test at all, clean system, indoors, and not a lot of rounds.
*** At some point in the past I bought a bag of tungsten weights. If you have an A5H1, you can then make the A5H2-3-4. The A5H0 comes with an AL weight for the bias spring and cannot be swapped out. Cool Story Bro - If anyone wants some weights to mess with, let me know and we can work something out.