A basic scientific law is;'Every force has an equal and opposite force". In the case of any gun/rifle the opposite force to that created by the detonation of the cartridge/shell is the recoil we experience.I would expect that the weight of your 10G complete with Chambermates is heavier than your 12G. This being the case you will experience less recoil with the heavier gun for any given shell.Another factor that can influence recoil is cartridge head space, if excessive this could be another reason for increased recoil experienced with your 12G. In so far as velocity is concerned, once the charge leaves the confines of the 12 G Chambermate and enters the 10 G barrel, velocity may be reduced due to the increase in bore diameter/volume. It would seem logical that a 12G wad would not be an efficient seal in a 10.G bore[ie;diameter increase is.046 inches] Perhaps Chambermate has carried out tests to determine the impact on velocity as the charge enters an over size barrel?
