A friend and I have the Lee 3R mold, I use ww's +Tin and Chilled shot and cut a rabbet for a gas check with a lathe.
The air cooled bullets are BHN 11-13, depending on batch, When I water drop. I get BHN 18-20.
I use liquid alox and LBT soft blue, both do well, up to 1600fps for my handirifle with the 3R and 1800fps with a 325gr RCBS, no leading at all.
My friend had a lot of leading problems with speeds over 1400 fps with his BC, even with chilled shot added. Waterdropping and double dipping in liquid alox helped, but the real improvement came after I made him a little machine to cut a rabbet for a gas check, he is now getting 1" 100yd groups with waterdropped , double dipped, gas checked 3Rs and no leading, even at 1750fps.
So far, seems the 3R is good for 1200fps as is, but to really move it, either adding a lot of linotype or heat treating to get a much harder bullet, or add a gas check.
Might be a good subject for a group buy from Lee.
Don