Mark O asks in comments:
I am a pistol guy. In a pistol with lead you have to be concerned about leading above 1000fps. What about a rifle?With the proper bullet alloy, and good lube, bullets can be pushed much faster than the 1000 fps limit. My favorite cast bullet load for the .357 magnum runs a hard-cast, gas checked bullet of my alloy out to almost 1200 fps with a 180 grained bullet. That same load from a rifle give me almost 1600 fps with no problems.
I push my favorite .30-30 load to about 1800 fps with no leading.
On the other hand, I can push a soft lead bullet out of a pistol at 650 and get leading. It's a function of alloy and lube. My heavy cast loads are normally cast from good alloy, dipped in liquid alox, the the gas check is applied, then it's dipped again in alox before I load it.
You never know what a cast bullet is going to do in your barrel until you try it. It's all part of the trip down the worm-hole.