It has been my experience that wheel weights with 2% tin added will expand down to about 1700fps. I generally use a 50/50 mix of wheel weights and pure lead plus 2% tin. That will give me expansion out past 200 yards with a Lyman 311041. Without over expanding at 25 yards, if muzzle velocity is around 2,000.
That velocity number may be correct for one particular bullet you're using, but it varies a LOT with meplat size and nose shape. A wider meplat will generally expand at much lower velocity, and may come unglued at higher speed. A round nose, on the other hand, usually requires more velocity to expand. The hollow points in my picture above obviously expand well, and they only started out at 1,000 fps.
I try to avoid overgeneralizing about this stuff because it lead to some very flawed conclusions.
Personally I have come to the conclusion that large meplat bullets are undesirable for most rifle loads exceeding ~2,000 fps or so, unless combined with harder alloys to limit expansion (and that only works to a certain extent). I have also learned to not bother with softer alloy noses in rifle bullets for use over 2,000 fps or so even with very small meplats; it's just unnecessary unless you're trying to make the nose blow off on impact.
Low velocity (like black powder rifle or handgun speeds) loads are a different thing entirely, and can benefit from larger meplats and soft alloys where appropriate.
