Got a Snowpeak SP500 pistol to try darts, the only .22 darts I could find are these Milbro Black 0.222. It does 4 fpe with 14.3 grain CPHP at 355 fps. These are about 21.2 grain, I average 50fps or 0.12 FPE with them. The package says they are mild steel. After shooting I see no rifling marks...