Here is a little shotgun 101. To understand why a gun kicks, you have to understand the dynamic of a loaded shell. When you fire a loaded shell in a gun you are simply detonating a controlled explosion in which there is only one exit (the barrel). But that exit (the barrel) is block by a heavy object (the bullet). The explosion desires to be released and is pushing against the bullet and propelling it down the barrel. If it did this slowly, there would be no kick, but because it is doing it extremely fast it creates a lot of back pressure in the reverse direction of which the bullet is traveling. This back pressure is delivered to the gun, which in turn is delivered to your shoulder. The larger the explosion ( size of the loaded shell) the harder the back pressure. This is why a 12 gauge kicks harder then a 20 gauge. But the design and type of the gun also play an important part in how much back pressure is delivered to your shoulder. How you hold the gun is of even more vital importance. How you hold the gun is the difference between whether you just feel a kick or you end up severely bruised. Break over long guns (rifles or shotguns) are going to kick the hardest because they deliver almost 100% of the back pressure to you. The only back pressure that is not delivered to you is that which is absorbed by the weight of gun. Cheaper break over long guns are often made with less steel (to save money) and they are therefore lighter which makes them kick even harder. So if you are going to shoot a break over, find the heaviest one you can buy. Blot action and pump shotguns also kick hard, but because they employ a lot more parts, they are usually heavier and this makes them kick less hard then break over long guns. Semi autos kick less harder then break overs, bolt actions and pumps. The reason they kick harder is two reason. 1. When the shell explodes, part of the energy created by the explosion to eject the shell from the gun. The shell is not pushing directly against the gun as it does in break overs, bolt actions and pumps. When the explosion happens, the shell pushes against the bolt pushing it backwards. So the some of the back pressures is absorbed by the bolt which as a spring that absorbs the impact. In some guns, gasses are also employed to create a gas cushion which further reduces the kick. There is a huge difference between semi autos and how much they kick. Really expensive 12 gauge shotguns like those made by Benelli are know for how little they kick. Stoeger makes a knock off of the Benelli which is just as good for 1/3 the price. I hope this help.