Soft lead bullets shot below 900 fps should not lead if the bore is not rough. I suspect, I cannot prove it yet, that some powders cause more leading than others.
Hard cast bullets may lead at velocities below 900 fps because the gases are not present in enough force to obdurate the bullet to seal the bore.
Supposedly the problem with leading, besides a rough bore, is that the bullet does not seal the bore, the gases rush past the base and melt the sides of the bullet to the bore.
So whether it is soft lead or hard, if the bore is not rough, if the velocities are enought to obdurate the bullet and seal the bore, leading "should" not occur.
At least this is how it has been explained to me. I suggest a visit to the website for Desperado Bullets [
http://www.cowboybullets.com/] and you can read their suggestions.
Also supposedly flat-based bullets are better at sealing than bevel-base.
You also could try a wad on top of the powder and below the bullet base as black powder cartridge shooters do. It serves as a gas check. But it is another reloading step and in the case of handgun cartridges it might be a pain.
I have currently been shooting hard and soft cast bullets out of M10s and M19s and am getting no leading at velocities running from 850 fps to 1200 fps. The higher velocities in the .357 magnums only!
As a last resort, the easiest, and it is easy, way to clean out leading is to go buy some copper "Chore Boy" scrub pads at the store. Pull out as many strands as necessary and wrap around to "fatten up" your proper caliber brass bore brush. Scrub the bore with this rig and almost all of the leading will be gone in quick time. Then use a lead away patch to clean out the rest. It works better than the "Lead Out" tool kit. It is easy and quick.
Lead bullets are cheaper than jacketed, they are found more readily, they will kill [I only know about game animals] as well as jacketed, and are easy to use once they are "figured" out.
I hope this helps.