Bronze round wire is perfect for use with BronzClay, CDA #521. It's the perfect alloy (92% copper and 8% tin). The melting point is 1880F. It is dead soft but is stiffer than other metals in the same gauge.
If you are going to solder on your piece and this wire is part of your design, the flux will deplete the tin. This may cause the piece to appear copper plated when removed from pickle.