Well I’m speaking as an opinionated caster/shooter who has absolutely nothing scientific to back up my thoughts.
First off I have lead from various sources of generally unknown makeup. But it works which is good because I can’t afford buying from Roto Metals other then 5 or 10 pounds of this or that to harden an alloy, mostly tin. I love Roto Metals by the way, just makes for spendy bullets. For a few years I was enamored with the HP casting and bought molds from NOE and quickly became somewhat disappointed with one the pin design which can be a pain in the rear to get set right for casting. The other is, obviously this depends on the bullet you’re cast for, rifle or pistol.
For handguns it’s all dependent on velocity. Too much, stuff blows up, to little velocity and not much improvement.
Outpost has the answer there with a known quality of alloy.
But in my “use what you have world” I’ve ditched the HP in rifle bullets and either use a flat or cup point pins.
I handguns at lower velocities cup points work for me if I’m using a HP mold.
But as there are many variables what works for me is softer alloys, 30-1 with powder coating to hold things together.
But with traditional lubes 20-1 works pretty good so far.
I have a fair amount of CWW lead but I rarely use it because of moving diameters and hardness.
I do use CWW for some rifle bullets once they have aged, some Powder Coated and about half lubed, Ben’s Red, then coated BLL.
I admit I don’t have the experience of many on this Forum but I’m working on it.
Powder Coated bullets have opened up a large change in the velocity and hardness of bullets used. But the added diameter of .001 to .002 can cause a difference problem with certain molds. That’s where traditional lubes really shine.
But HP fracturing if the alloy is too hard or a bone is struck, unpredictable is not for me. Too many variables. Softer, bigger flat point, more weight, moderate velocity.
Anyway that’s my 2 cents and I’m probably over changing here.