1st; Bore volume is based on the Square of the dia, not the dia. Thus the volume of the .775" bore is 13% more than the .729" bore, not the 6% stated.
2nd; Assuming the wad obturates & seals the bore, even though the pressure dropped by 13% it would be acting upon a 13% larger wad base so velocity should be unchanged from this cause only.
3rd; Recoil is based upon wt & velocity of the ejecta, not pressure. As the wt of the charge is unchanged the only thing to affect the recoil is developed velocity.
4th; While on average larger gauges weigh more this is not an automatic given, there are some 10ga guns which weigh less than some 12ga guns. If the two guns weighed the same & velocity was the same the recoil would be the same.
"IF" the velocity is actually increased as claimed by the makers, even though pressure may have been reduced, recoil will be increased in proportion to the velocity increase.
