In an attempt to get this post back on track... Regarding recoil, put simply (in round figures), reduce the velocity of the cartridge by 10%, you reduce free recoil by 20%. Reduce the shot load by 10% and you again reduce free recoil by 20%. Reduce both by 10% and you reduce free recoil by 40%.
So going from 1oz @ 1350 to 7/8 @ 1200 (both changes are around 10%), in a 7lb gun, you reduce free recoil from 15.8 foot pounds to 10.1 foot pounds (actually 36% reduction not 40%, but hopefully you get the drift).
The gauge that you are using has NO effect. The weight of the gun has an effect, which is what battue was pointing out. If you are already using 7/8 oz @ 1150 in a 7lb 12g, using 7/8 oz in a 6lb 20g will generate more free recoil.
