I am not stating that this accounts for an appreciable amount of recoil, I was just saying what I thought was behind the design having only seen a little bit of information about it.
Making the barrel hard to rotate is exactly the opposite of what you want it to do though. You want to transfer the energy in to rotating the barrel. If you make it hard then there there is no point doing it. The easier to make the transfer of energy in to rotating the barrel the more energy you take away from it pushing the pistol directly back.
Once again, I can't say in practice how well it works, thats just how I saw it at first glance.
You are misunderstanding how energy transfer works. If it is easy to rotate, it's doing less to reduce or change recoil. If the barrel weighed 20 pounds, yeah it would have a noticeable effect.
I must be misunderstanding then because some of the things I have had to do in the past and calculate for involved taking rotation and converting it to linear motion. The Nm required was calculated based on the linear force I needed to overcome and mechanically works in the same way as the rotating barrel.
Having said I could be wrong, I could even be further wrong because I dont understand how saying F=ma proves that something lighter has more force? Only if a specific calculation has m*a greater would it have more force. Isnt the original force coming from the powder, the mass is the slide and the acceleration is then given from force and mass. A heaver slide will accelerate slower, but it has more mass and unless the force originally came from having less powder how does it have less force?