Hardness isn’t really a benefit with 44 special or starting magnum loads. I shoot both 50/50 pure/ wheel weights and straight wheel weights out of specials, at less than the 15500 pressure limit with good results.
Getting into magnum territory I use only wheel weights because the softer alloy leads. That could be my gun, my alloy, my techniques, and not the bhn of the alloy.
Could be the lube. If your commercial bullets have x lube, and you are using Y lube, that’ll make a difference. Or if one or the other is powder coated and the other is lubed.
There is no reason a 200 grain bullet shouldn’t shoot well though provided things are right with the gun, load, and techniques.