Grand,
Perceived recoil is dual-directional, you feel it in your shoulder as the gun attempts to move straight back, and you see it in the muzzle as it rises because the gun can't move entirely in a straight rearward position.
When we talk about reducing recoil, it's necessary to separate out what the two elements are that Vang's barrel work addresses.
The ports push the muzzle down, which reduces that part of the recoil you see and feel against your cheek.
The internal backboring & cone lengthening mechanically reduce the actual back-thrust that occurs when the shot charge first enters the cone (spreading it out over a longer compression period) and again when it enters the now-oversized bore.
Although it all happens too fast to register when the gun fires, those two "compression" points create part of the recoil that results.
Long way of saying that the porting acts in conjunction with the internal barrel modifications to reduce both aspects of perceived recoil, the part you feel on the shoulder and the muzzle rise.
Porting alone would address the muzzle rise, but wouldn't be as effective in overall recoil reduction as the full treatment.
Another note on porting is that not all ports are equal. Drilling CAN leave burrs, which would tend to tear up plastic wads, IF not polished out.
I didn't see any wads, conventional or Flitecontrol, that showed unusual deformation or tearing after porting.
Gmoats,
My occasionally hazy memory from the first shotgun Vang worked on for me about nine years ago thinks something was said at the time about the backboring acting to reduce velocities somewhat, and I added that to an email conversation with one of Vang's shop guys about the recent barrel work where he said velocities are lowered slightly as the end result of their modifications.
Could be wrong on the backboring & cone affecting velocity, but the overall effects I experienced in recoil & patterning still apply.
I have not chronoed any buckshot loads. Never had the interest in taking the time.
Denis