Are there just some bbls that don't like cast

[Fatdaddy]

I've had good luck with my 9mm and 45 cast boolits, almost no leading.
The .40 is another story. I slugged my BBL and it measures .401.
I lapped my mold out to .402 and it's dropping .402-.403.
I also bored out my Lee sizer to .402 just for size consistancy. I'm still getting mashed taters for about an inch or so then moderate leading the rest of the bbl.
I noticed that the rifling lands almost totally erase the tumble lube grooves on the boolit I slugged. Is this normal?
I have some Keade Cast with some sort of red lube and they lead worse than my home rolled.
Are there some bbls that just don't like cast boolits?

[918v]

Hammerforged barrels don't like lead. Large throats don't like lead. Too hard a bullet will lead unless it is a perfect fit in the throat. Some powders eat at the base of the bullet, vaporize the lead, and lead.

[Fatdaddy]

This is a Smith and Wesson MP40.
Using 5.6gr. of WSF @1.29 oal no FCD.
I've tried water dropping and towel dropping straight ww with a little solder. Can't tell a difference.
How much over (thousandths) can you safely go when experimenting with boolit size?
Could the case tension be swaging my boolit to a smaller OD?

[JLarsson]

How hard? How fast? What pressure?

[918v]

.005" ?

It depends on lead hardness and pressure.

I have shot .358" hardcast bullets in a .354" barrel at 35000 PSI pressure levels without any problems.

[Fatdaddy]

Could the case tension be swaging my boolit to a smaller OD?

[918v]

Only if you run the round thru a FCD.