It sounds like it was the cleaning. You need to use neck lube after a good water and detergent cleaning or wet tumbling. I bought some wet tumbled pistol brass, and even this pistol brass stuck to my expanding die and caused galling. In two different calibers. A pull thru rifle expander may have to work much harder than a pistol expander.
Sidenote: when you put tension on a tube of brass, it gets just a tiny bit longer... and a tiny bit thinner, too. So when the expander starts to stick in the neck, the harder you pull, the tighter it gets! This is why you often need neck lube to expand rifle cases, but not pistol cases. At this point, lube may or may not adequately fix the problem. Even if your dies are in spec, the case necks may be exceptionally thick.
In almost every case of dies sticking in brass cases it's improper or inadequate lubing. It's not the dies, it's not the prep and you don't need to buy more expensive dies, fix the lube problem.
My Hornady 7mm die must be exceptional. I'm a pretty strong guy, and I would not make it through 100 neck lubed cases with this die and stock expander.
you don't need to buy more expensive dies
Personally, I rather buy a $30.00 die than to neck lube every case and then either wash each case or suffer powder sticking and clogging the necks along with reduced neck tension/friction. If you have not had expanding problems, you obviously would not consider buying an alternative solution. When you do run into problems, remember the M die. Once you've used it, you might buy one for other calibers, even. No neck lube, less effort, no inside chamfer, more consistent neck tension even on untrimmed brass, better concentricity (if you are having problems), zero bullet scraping, being able to decap primers from problem brass without redundantly resizing/expanding or changing out the expander ball. Just a few of the side benefits.
You don't need a lot of things in reloading. You could get by with a Lee Loader and a hammer.
As many steps you need to mind in rifle reloading, it baffles me that all major die manufacturers think that combining sizing and expanding is a good tradeoff for the additional work it creates and potential problems it may cause.
Sidenote: I have also had problem seating cast rifle bullets concentrically, and I had some improvement with a competition seater die. But once I got the M die, the comp seater is now completely useless.
