204Ruger

One possible reason the first one stayed clean is you may not be drying your chamber while cleaning the bore.
A little solvent left in the chamber will act as a lubricant allowing the brass to flow easier.

Is this virgin or once fired brass? How are you sizing this brass?

It's once or twice fired, I don't keep very good track of that. I full length size using rcbs dies

Are you measuring the amount of bump your die is moving the shoulders back?

If you set your die to touch the shellholder your probably oversizing your brass which does not help your situation.

I have the die touching the shell holder, I set it that way because the instructions that came with them said to. Is there a way to set it so that it only neck sizes the brass?

Hmmm, it's been a lot of years since I bought any dies from RCBS. Seems they haven't changed thier one size fits all instructions. Shame.
Chances are high with a factory chamber your pushing your shoulders back much further than you need to. That's never good. Incipient case head seperation, Google it

You must have a set of calipers your using to measure cartridge overall length. You can buy a set of Hornady headspace comparators. One of the most important tools a reloader will ever buy. Highly recommended by everyone. Can you live without them? Yes, but it takes a lot of expierience and there is no replacement for knowing the real truth done by measurements.

But for now, yes, turn that die out one full turn and reset. Not technically neck sizing but it has to be better than what your doing now. I set up my FL dies that way with virgin brass.

Now the shoulders are the last thing your die will move. Somewhere between bumping the shoulders and not bumping the shoulders theres a sweet spot. Your shoulders will actually begin to flow forward/lengthen. The comparator makes this easy to see by measuring.
So if you turn your die out one turn and you feel resistance while chambering an empty piece of brass you can screw it out further ( for now) or attempt to set it deeper in tiny increments until resistance goes away. Once again, the comparator is the easy way to do this stuff.

Normal shoulder bump is .002". Once fired brass usually is .002" less than chamber dimensions already. That's why that sweet spot I mentioned is beneficial to find.
Some of your brass may be shorter yet as you've been having pressure issues.

I suggest the comparator.
A box of factory ammo if you don't have it. The fired brass from that should be consistently closer to your chamber dimension than your reloads that haven't been functioning correctly.
And if you want to get serious about accuracy Id also suggest a Redding S series FL bushing die.
I will never pull an expander ball through the neck of any brass I expect decent accuracy from. That beautiful carbon coating inside the neck is nothing I want to disturb,

'funny you mentioned the annealing thing RAMOS. Yes, I've had to do that to brand new brass even... Laupua even (for 6.5-284).

I was getting the "soot" thing also (savage bolt gun), and it happened to coincide with noticing that, while (lee collet) neck sizing, some cases didn't drag on the collet "like usual", and the bullets "seemed" (oh, man I hate those feely-creepy indefinite words.. usually used by left wing liberals that cannot define the word "truth"). To keep thing short, after annealing the brass revived and the soot stopped. Not a scientific study by any means, but I believe the brass lost its joy and did not seal up well under fire. Who knows…

The laupua I use gave the same effect right out of the box. Joy returned after annealing.

BTW Joe, always appreciate it why you wander in. I've been using you shoulder bump advice with excellent results.

I've been away quite a bit too.

I meant "when" you wander in, LOL!

Ok I picked up some more tools and measured a once fired factory hornady case and compared it to a few of my resized cases, and length to shoulder differences were between .0035 and .004. I also picked up a neck sizer die and will give that a try as well.