I run three Redhawks and a couple of GP-100's. I size .358, 410, 430-431, and 452 and have no issues with leading unless I try to run alloy too soft for the loads or anything above around 16-18 BHN.
Most of my loads run on the hotter side for cast loads as I use them for hunting. I actually blended the alloy up to handle the velocities I might hit with each caliber respectively. I use two different ones, the first will do wonderful up to right at 1100fps and then smears terribly, the second works up to around 1600 as as far as I have pushed it in my 357's and 41.
As for the issues your having, This is what my 41 looked like with only 4 rounds through it using the first alloy I mentioned. The first couple of inches,
Pretty much the rest of the 7/5"
Same alloy as the 41, but in my 45 Colt, and after putting over a hundred plus rounds through it,
Now that said, I ran the second alloy mentioned cast in some 180gr HP's through the 41 up to 1600fps and it looked pretty much unfired except for some powder residue. Same with the 357's using a healthy dose of AA-9 and some 160gr HP's up into the 1350fps range. These were all lubed using Carnuba Red and sized as stated above. In my 44 however if I try to use a hard alloy it just pukes out lead like an extrusion machine. I have to keep things at or under the above mentioned BHN with it. The GP-s will do the same thing, but I believe on them it is more due to not being able to run the bullets hard enough. Even so I found what DOES work through them and I'm sticking with it.
I also run the Lee 452-300RF cast with air cooled WW, sized to .452" and lubed with two coats of Alox, once before sizing and once after, through my Raging Bull at 1550fps with no issues.
I'm not saying I'm an expert at this but something is giving you fits and it is sounding like you might have the thread squeeze issue in at least one. I have only heard of it being a real pain in the RH's, but I might be mistaken. I would for sure get them slugged to find out, and if that is the case it isn't a huge deal to remedy it, just a bit time consuming. The cylinder thing is an easy fix, and I have heard of more having that problem than anything else. If your choked down in the beginning your never going to get a clean shooting barrel with cast. They just don't squeeze down then get fatter again once the pressure get around them.
The biggest thing with cast is finding what DOES work and that is a big balancing act of alloy verses pressure. You might WANT to push a bullet to X velocity with Y alloy but sometimes you don't get what you want. I foudn that out several times while working up my two blends and it's also why I HAVE two blends I use. I could use straight WW, for 99% of what I shoot and do if I am casting a solid. I just happen to like shooting the HP designs and worked through trial and error to get what I needed. Trust me I had plenty of barrel cleaning time before I got to what worked in them all.