Rip van Winkle personal Musket is a one-man anti-aircraft arsenal with "magic bullets" that rip through jets and tanks.
These magic bullets can change their trajectories in mid-flight and repeatedly pepper a target before expiring. Rip seems to have a limited amount of these bullets, as she only uses one at a time. In fact, she uses only five on-screen before her death throughout the entire series and only one directly against Alucard (so far: she might use them again during The Dawn.) It's possible that this could be due to the fact that she has to go through the process of manually reloading the musket after each shot, forcing her to rely on taking out all of her targets with a single, decisive shot during engagements. (This is an article about her gun. Way too much info on her powers before hand.)