Strange rust in Kimber barrel

[Beaux Nehr]

I'm anal about keeping my firearms clean, but recently (yesterday) upon examining my barrel with my super bright Surefire I discovered a weird, crimson colored rust on the lands of my barrel. Really strange.

It's not visible to the naked eye (well, the rusted area only looks cloudy to the naked eye.)

I went to town with CLP and a bore mop (the only things I have available since I'm not at my house) and it slightly cleaned up the surface rust.

I have no idea where this came from, as the only thing I've done differently recently is to start reloading using lead bullets and WST as the powder (CCI primers.)


Otherwise, I have no idea where or how this rust started.
I plan on covering a bore mop in IOSSO bore paste when I get home and scrubbbing the crap out of it.


I'm pretty disconcerted by this, as it's never happened before, and I'm super careful with my stuff.

 

[Beaux Nehr]

So I've been working my butt off trying to get this crap out.

All of the surface rust (that's all it was) is gone, except for the tiny line that runs down the right angle where the grooves meet the lands.

I just can't get to it.

Any suggestions?

EDIT:

Got everything I can see out, but I'm still feeling a little leery.