20 ga. Chamber length

[Spin Drift]

Unreformed engineer here but when I did these calculations about a decade ago a 1oz load at 1200fps was 16 pounds force. (this was my standard Clays load for skeet and sporting clays). When I started to shoot International skeet, I made up some 1 1/8 oz loads at 1550 fps for second shot at stations 3, 4 and 5. These forced out at 35 lbs of free recoil. You had to be a man to pull the trigger a second time. I only used three of these shells per round.