The only time I've gotten sooted necks and bodys is when the cases needed annealed, other than that I can't see a problem with what you're doing. 10,000 psi is all it should take at most to expand the case and seal it up good. If it isn't doing that I'd anneal them. When they get hard and brittle they just won't open up and seal. Some of my Ultra brass seemed awefull hard to begin with to tell you the truth. I noticed this when my brother first got his too. The necks seemed a little thicker as well.
If you use a hack saw or dremmel to cut off a short ring on a cases neck, chamfer and split this ring, seat a bullet into the short necked case now, slip this ring over the bullet and leave it out long. When you chamber this round the chamber will push the ring back when it hits the end of it, pull it out and measure the cases OAL now.
This will tell you the trim to length, I trim to .005" shorter though. My 300 Ultra is exactly 2.840" to the end. Don't outside chamfer the end of the ring that hits the end of the chamber too much or it will stay out farther than it should.
I've got dented cases just exactly as you describe too, just a little "below" the shoulder and running length wise about 3/8" long and 1/8" wide.... they all came from my **** FL sizing though. Didn't matter what amount of lube I use either. Something I've just lived with basically.
How old is your brass?
