Several things cause leading. Soft lead, rough bores, driving the bullet either too fast or too slow. The only way to fix the soft lead is to get a hard cast bullet from a reliable source. Personally, when I shoot lead it is from Lasercast
I read with great intrest all the misconceptions of shooting cast bullets.
1. It is a myth that when dealing with hadgun bullets that shooting soft lead causes leading
Many years ago when I was shooting a .44 magnum I got leading even with hard cast bullets that were gas checked, properly sized and had a good lube on them Why?
I noticed that dead soft factory ammo with only 3 per cent antimony added gave no leading at all even at high velicities. Why?
It you want to reduce leading It may be that you are using to fast a burning rate of powder and in too large a quantity. In my .44 magnum experiece simply by going to a slower burning powder did the trick. I went from a bore that was coated with lead to vertually no leading whatsoever.
2. Myth 2 , rough bores cause leading. ONce again in my experiece pushing rifle bullets as fast as 2,000 fps I got very little leading even from military bores that had been damage from shooting corrosive ammo out of them. The bore has to be extremely pitted to pick up a lot of leading. It can happen if the bore is really bad but then the weapon usually needs rebarreled and will not accurately shoot even jackted bullets for very long before fouling out.
What does cause leading besides to fast a burning powder.
1, Undersized bullets
2. Poor types of lubes
3. Not using gas checks when approaching 2,000 fps. They are not necessay for most pistol velocities.
The one big draw back of buying store bought cast bullets is one of quality and also one of size. When casting your own you can size it to fit your particular bore.
I also do not like the plastic lubes most commercial bullet casters use. I find the lubes inferior to the old NRA 50/50 alox formula.
How I clean out leading.
When shooting 9mm's fast on a hot summer day I sometimes do pick up a minor amount of leading. I simply us a .35 caliber rifle brush and some Hoppe's no. 9 and run it back and forth though the bore until the leading is gone. It takes about 30 seconds of back and forth scrubing or about 100 to 200 strokes. Sounds like alot of work but it is not. It only takes about 30 seconds of work.