Those little FM transmitters are probably not going to get you more than a few feet. Not a lot further than from the ipod to the car stereo. I've never used one so I could be wrong, but that is what they are designed for. Unless you used some larger powered transmitter, like for those home wireless music systems.
You could use a long cord spliced to allow plug in directly to your radio. You probably would want to figure out some way to plug in the ipod to a larger battery source, as the battery is small, and they typically use only a very small current to make the music in the ear buds.
Sound like a cool idea overall if the technical hurdles can be broached. You have to love the interface of the Ipod.
Bullets have well documented performance specifications.
Min Velocity info is available, and describes the performance floor of the bullet... DON'T allow yourself to reference F.P.E. as an accurate descriptor of killing power.. You are smarter than a copy editor, and you understand that you can determine maximum (reliable) effective range by comparing your drop chart to published bullet data....... And, dog-on-it, people like you!