Here is some information that I posted back in July after my first attemt at shooting fireworks. I hope this helps.
I took my camera and set it up on my tripod and used a cable shutter release for mine. This was the first time that I ever tried it and I think I got some pretty good results. The times varried. I had the ISO set at 200, with the shutter set to "BULB" setting, picked what looked to be a good spot in the sky and would press the button and let it go when the explosion was over. Sorry it's not more definitive, like I said it was just hit or miss for me.
All were taken with a Nikon D80, Quantaray 18 - 200 set to 95 mm, F10, and these are all JPG file straight out of the camera with no processing at all.