I haven't chronoed such a load, but my gut-estimate would be you're in the 1000-1200 fps speed range. That shouldn't be excessive for a plainbase cast bullet, BUT, there are alot of factors that affect leading and accuracy. You should start with a barrel that has been thoroughly cleaned to remove any and all jacket fouling. The cast bullets should be sized to the throat of the chamber, and typically at least 0.001" over bore dia. The bullet lube should be on the softer side, and the bullet also shouldn't be too hard. The base of the bullet should be flat.
The absoulte worst leading bullet I've ever shot was a commercial hard cast .357" 160 gr truncated cone swc w/ a bevel base out of a 35 whelen. I was using fairly mild loads, unique for 1500 fps. The combination of the hard bullet, undersize bullet, bevel base and crappy hard lube made for bullets that leaded in long strips in the barrel. It was a serious chore removing the leading.
While gas checks aren't always needed perse, they typically make for bullets that are less likely to lead, and are more tollerant of conditions that would lead to leading. I see them as cheap insurance if you don't cast your own bullets. When you cast your own bullets you can tailor the bullet alloy, lube and sizing to your gun, and hence plain base bullets work fine in many applications. But with storebought bullets, I see gas checks as worth their price.
