What are the possible causes of leading and how best to remove it?

Thanks for the reply. It will take a year or two to gather that data. I’ll be back.😂😂😂😂👍👍

I’ll take some measurements over the next week. Thanks again.

To add to RSW's questions:

Barrel length
Bore condition
location of leading

My only two causes of leading, regardless of other factors, are to hot of weather and wrong lube for those temps and under size bullets.

If breech seating make sure your seating deep is enough to seal and not get blow by.

I shoot a .32 caliber bullet .002" wider than my groove-to-groove diameter 11.5 twist barrel using 20:1 lead:tin alloy with Alberta Schuetzen Lube at 1,526 fps and I have NO leading after 120 rounds even at 110 F.

Much of the leading occurs from using an alloy that is too hard so the gas goes around the bullet instead of having the base properly seal from the bumped softer alloy.

Or the bullet is too narrow that allows gas cutting around the bullet.

I have used 20:1 alloy with .002" wider bullets with all calibers from .25 to .50 caliber without experiencing leading even with plain base cast bullets even at 1,856 fps.

When breech seating make sure at least half of the base band is engraved by the lands to ensure you have a good seal.

My base band is completely engraved when I breech seat.

For fixed ammo I ensure my bullet concentricity is within .001" to ensure I do not get shaving of a tipped bullet when it enters the throat.
This is achieved by using unsized fired cases, using an inline seater and compressing the necks for consistent neck pressure after I have inserted the bullets (using a neck seater with the depriming rod removed).