It may be over simplified but a good place to start is:

Every 100fps of velocity ='s 1bhn

If your load/bullet is doing around 800fps you need to look for a 8bhn bullet. The bullets alloy/velocities can over lap meaning you could use a 8bhn bullet for a 900fps load or a 10bhn bullet for a 900fps load.

Using this simple formula will get you in the ballpark.