Maybe I should clarify just a little. I make .30 cal bullets in a set of steel dies which take more lube than carbide dies. My .30’s come out feeling a bit greasy. So i degrease them. I make 6mm bullets in a set of carbide dies which take much less lube.
To Joe's point, there can be more lube remaining on the
inside of the jacket (directly behind the metplat) than we'd think.
With tumbling to lube the jackets, it's inevitable that some lube will migrate into the jackets. Some could get there during core seating. With a core seat operation where the cored jacket is placed on the seating punch and the die is then advanced over the jacket (like a Blackmon setup), the forward edge of the jacket can't pick up any lube off the die. With a conventional setup, I can see where that could happen.
There's also more clearance between the non-core seated jacket and the die before the core is seated and the jacket expands up. Maybe that bit of clearance lets the jacket 'scoop' a little lube on it's way up the die until it stops at the core seat punch?
When pointing, there's less clearance between the jacket and die. Maybe that either helps...or adds to... any possible forward edge 'scooping'?
When the point is formed, there's a helluva lot of pressure in play. There's certainly lube that lives in that area of the die and around the ejector pin that can be forced into the developing metplat as the point is formed.
I stumbled on this quite by accident. I was looking at the metplats with a loupe and for some reason, I just tapped the point end of a bullet into the palm of my hand. There was a little grease spot on the skin. After soaking the bullets in acetone, I did it again. The spot was still there. But it seemed a bit 'diluted'...for lack of a better term.
Tumbling the bullets in acetone was the next step. No more grease spot. And the acetone was dirtier than I would have imagined. Remember, these bullets had previously been soaked in acetone once.
I'd never say this is a real deal with every set up. Lube, dies, lube amount and all the other vagaries and subtleties are certainly involved. At the very least, it's something interesting that can be checked.
Heck...even it there is a bit of residual lube inside, it could be flashed off instantly by the heat when it's on the way up the barrel.
Thoughts????
Good shootin'

-Al