The original question here is, " How fast can I push a cast, un checked bullet from a 44 mag?"
Let me tell you what I have found in my 30 years of shooting cast bullets.
The variables in how fast you can shoot cast bullets are many. I will attempt to list them but may leave some out. They are:
Bullet alloy, Bullet design, Your gun, Primers, Powder, Lube, sizing diameter, Your location on the earth, and what you need the bullet to do.
In a nutshell, no matter what anyone else will tell you, you can push a cast bullet until you get lead in your barrel, at that point, you need to clean your barrel and back off. Sometimes you have to shoot the bullet slower but maybe just changing the lube or alloy will alow you to go to an even higher velocity. Sometimes a good load will start to lead in the summer when it gets hotter than you have been shooting it. Sometimes changing primer manufactures will cause lead to form.
After a while you will get a feel for how fast you can shoot cast bullets in different situations and avoid leading, just from prior knowledge.
Some of the things that I have found that work are:
If I get lead from a commercially cast bullet I lube them with Lee liquid alox and try it again. Most of the time it works.
If a bullet is designed for a gas check, I use a gas check. I have shot lots of bullets, so designed, without gaschecks but I always get better accuracy with those bullets, with a gas check.
The base of the bullet is the steering wheel of the bullet. To get good accuracy, it has to be close to perfect. As a result, some guns just shoot better with a gas check design and a gas check installed.
I have never had consistent accuracy with bevel based bullets. Some people have had good luck with them but I haven't. I just sent a mold back to Lee to get a bevel base removed.
I usually get higher velocity, in some cartridges, with cast bullets than I do with the same weight of bullet that is jacketed. These include most pistol cartridges and older, long necked, rimmed, rifle cartridges, like 30-30 and 22 Hornet.
Most of the time, I get the best velocity with cast bullets using faster powders. This isn't always the case but I try fast powders first and usually stop there.
Accuracy almost always wins over velocity. You got to hit it before you can kill it.
I probably didn't answer the question, but I feel I have given good solid advice.
Sixgun