Two suggestions for you...
the first is that there are two sizes of bracelet memory wire. You probably have the regular size. You might have better results with
http://shop.rings-things.com/cart/pc/showsearchresultsCustom.asp?pageStyle=M&resultCnt=10&keyword=61-167&submit=Go+%3E%3Einstead.
The other suggestion has to do with the size of the beads you are putting on the wire. Tiny beads like seed beads will make a bracelet that just about matches the size of the memory wire without any beads. In my experience, medium size beads will sometimes make the bracelet fit a little more loosely. It seems like they barely effect the shape of the wire, not misshaping it, but relaxing it. Very large beads will take up more room inside the wire, effectively reducing the overall circumference.