Very interesting..... in a geeky sort of way.
Travis, you've tried several shots with this weird configuration, so I thought I'd give it a try, too. This is just a first try to see if it would work at all, but there will be more tests coming.The projectiles were made to fit my .51 cal mule test bed gun. 340 cc tank, 30" barrel.The ring wings on this first attempt were made from gray PVC barbed fittings for water lines. O.D. was turned to about .503", and a slight I.D. taper was added at each end. I.D. is .405" . Lengths are .61 (13.3 grains) and 1.33 (27.8 grains). The pusher disc (sabot disc?) is made from UHMW and is a slip fit into the tubes and weighs 11.7 grains.To get a baseline for the shots, I first tried a 250 gn bullet at 1100 psi, with medium hammer force setting.That shot was 659fps and used 200 psi. Air efficiency was .84. The calcs for that shot show that the valve closed when the bullet was about 2/3 of the way down the barrel.Without changing any settings, I loaded one of the 13.3 gn rings, with the 11.7 gn sabot. Total weight was 25 grains.The air for this shot was a tad higher at 1150psi. The ring and sabot did not separate, and went across the chrony at 1101fps. Air used was about 350psi. The spreadsheet calculated that the velocity should have been about 1400fps, and that the valve did not close until after the ring was out of the barrel. Why was the velocity only 1101fps when the prediction was 1400? I don't really know. However, it does seem that the spreadsheet has a tendency to predict too high of a velocity for light weight, high vel, shots.Unfortunately, because the sabot did not separate, they are now lost inside the hundreds of plastic grocery bags inside my bullet trap. But, at least it fired and went across the chrony. Next step will be to make some more parts and take it outside to see what happens. If all goes well, then lead rings will follow.Lloyd