its more about the camera than the program
It is more about the camera that the program. Any free program you get online can bring down the frames per second on your video, but only down to 30 frames a second, which is the recording limit of most cameras. If you have a camera that sports a "sport" mode that shoots at a higher frame rate, you can drop this even lower, maybe to around 60 frames a second. Still, at 300 fps (a low end airsoft gun), it will still barely be in frame, and very out of focus. Sorry. To get the correct equipment to get a good shot of a flying bb, you will need expensive equipment. But you can get decent results for free.
No program is capable of that, the speed at which you can capture is determined by your camera. Standard camera only capture at around 30 frames per second (FPS), to slow to capture a fast-moving projectile. If you want to do that you will need to invest in a dedicated slo-mo camera, but be warned that they can be VERY expensive.
Youtube.
