Ok, here's what's happened.
A buddy picked up some Hi-Tek coated 9mm bullets that were sized to .358. Loaded them to a middle of the road load and shot them through a Springfield XD. The last inch or so of the barrel leaded really bad. Rest of the bore was clean.
Coating passed all the tests.
Where did we go wrong with this?
I've shot the same alloy, 50/50 pure/COWW, through my 10mm pistols hat higher velocities, with the same batch of Hi-Tek and had no leading.
It seems from what I've read here that the 9mm seems to be the problem child when it comes to leading.
He picked up some more of the same bullets yesterday, he's going to load them in .357 and see if they lead there. The bullet is the Lee 358-125 RF.
Another strange data point, those bullets where shooting high and to the right for him. He's a great shooter and at 15 yards these loads were shooting 3-4" to the right and 4-5" high. He bought the target to the house to show me.