Here is an example of bullet shot at 40 000 fps using Phantom v12 prototype in a clear summer day, lit by sunshine only:
You will probably need several tests before choosing the right speed for your specific needs, depending on bullet type/speed (pistol or rifle) and the amount of powder, available lights or sunshine, required resolution, framing (super-close-ups need higher frame rate), etc.
For certain type of bullets (980m/s or more) even 120 000 fps might still not be enough... Up to about 100 000 fps sunlight can provide you with nice even (and flicker free :)) light source. For higher speed you might need big mirrors (curved/parabolic mirrors are better, as it can concentrate the beam).
If you are aware about the exact camera trigger moment, you can use a time machine: http://www.bmumford.securewebsites.com/photo/camctlr.html
If color image is not a must, you can also have a look into different black&white high-speed camera models. Here is an example of bullets captured up to 1 million fps:
My reply came a bit late... but hope is still helping.
Diana - Phantom technician