I have found that if you push the velocity of a pellet much beyond Mach 0.8 (~900 fps) you start losing a large piece of the additional velocity in the first few yards.... The new version of ChairGun, based on the GA (airgun) drag model, produces the following graphs for residual velocity for a typical round-nosed pellet....



To compact the charts I cut the bottom off them, but the X axis is 100 yards, with the light vertical lines being 5 yard increments and the heavier ones being 10 yards.... The upper left graph starts at 700 fps, so the entire chart is right near the plateau of Cd at it's lowest value (ie basically a constant Cd model), and the decrease in velocity is nearly linear, with 60% of the muzzle velocity remaining at 100 yards.... Only 5% is lost in the first 10 yards and 10% in 20 yards.... The upper right starts at 900 fps, and you can see a slight curvature at the beginning, losing 6% in 10 yards, 12% in 20 yards, but then the line tracks the same slope as the 700 fps version, and is down to 58% at 100 yards.... The lower left chart is at 1100 fps, and the curvature at the beginning in quite marked, the pellet losing nearly 10% of its velocity in 10 yards, and about 17% in 20 yards, with 55% remaining at 100 yards.... Push the muzzle to 1300 in the chart on the lower right, and the pellet loses 15% of it's velocity in just 10 yards, and about 23% (300 fps) in 20 yards.... At 100 yards, it only has 48% remaining....

I've measured the loss in velocity over the first 5 and 25 yards of flight with several weights of JSB Exact pellets, and I've found that as you push the pellet over about 900 fps, you start losing a large percentage of the muzzle velocity in the first few yards.... To me, that is just one more reason to stay below the transonic region.... One experiment I conducted with a MV of 1101 fps using a .22 cal JSB Exact RS, showed that the pellet lost 64 fps in just 5 yards (5.8%) losing 11.3% of it's FPE in that short distance.... Interestingly, that is just what is predicted by the 1100 fps chart above.... Another test I did, using a 14.3 gr. JSB Exact Express at a MV of 1067, showed the velocity was down to 857 fps at 25 yards (80%).... which is just a bit worse than predicted above.... The very same pellet, starting at 901 fps was cruising along at 789 fps at 25 yards, only losing 12% of it's MV instead of 20%.... My calculations show a BC of 0.024 at 901 fps, dropping to just 0.014 at 1067 fps.... I simply can find no evidence for a constant Cd drag model.... If you push the velocity into the transonic region, it costs you extra air to do that, and you give most of it back in the first few yards.... You have to ask yourself if it's worth it, or if you should switch to a heavier pellet....

Bob