big al , that looks interesting !
In addition to understanding the physics of the recoil we did some serious testing . Tombstone --There are many gadgets that are really scams and people who don't know the science etc are taken in .That happens in almost any field.
I was part of a test with some very good ,very experienced sporting clay shooters .Two identical Browning SC guns were used, one with and one without porting .A round of SC was done by shooting half the rounds with each gun. The shooter was asked if he could detect any difference , and the watchers were asked if they could see any difference.
No difference was seen or felt with target loads.
Pure target loads made by companies like Remington have powder carefully chosen that will burn all the powder completely within the barrel.That removes any jet or rocket effect that is reduced by porting.
The porting however will act on powders that are burning outside the barrel and reduce recoil.
It's all physics but they don't teach science in schools anymore !