I've had good accuracy with WW alloys to about 1,800fps without leading, using normal alox/BW lubes. Lyman's moly lube and LBT's Blue will allow somewhat higher speeds with the softer alloys.

Much depends on the peak pressure of the load and time to peak pressure as well as how much over the 'ductile' barrier pressure one is shooting can determine how accurate they shoot and how much leading, if any, will ocurr.

Of course, the harder the bullet, the higher speed it can be driven. I've driven 275gr. FN's from a H&H at 2,700fps with MOA accuracy and no leading, using LBT Blue - so much is possible & there's lots of room for experimentation.