I am right now on a mission to find out why some loads work in a 20 ga. and many do not. I was informed recently, that slower burning powders do not work as efficiently as faster burning does. That has also been my experience.
The question really comes down to this. Many of the choke tubes we get today, are all tapered. Even in my various gauges, this seems to be the norm. Even with Briley extended, the parallel is extremely short. Would longer parallels, in your opinon, help stabilize the shot/wad, even with slower burning powders. I do know the tapered chokes work well with nickel plated shot, but with lead the patterns get blown.
I am planning on calling Brileys next week to seek out their opinion. Yes, if shooting is critical, I will go up in gauges.
I do know there are centuries of experience here and would like to hear what you have to say.
Lenard