After reading up on the matter, it would seem to me better to ultrasonically clean brass. Thoughts? Quote From Redding Reloading Website Please note that the inside of the case neck should be cleaned with a nylon or brass bristle brush before lubrication is applied; a few quick passes is sufficient (see image #8 below this paragraph). Cases should then be wiped free of dirt or debris but they do not need to be tumbled, ultrasonically cleaned, or otherwise polished before the resizing process. Extremely clean or highly polished cases have a higher coefficient of friction than lightly tarnished cases, making them more prone to sticking. My thought is that the oxidation on brass acts as a lubricant. Quote from an old –time reloading dude (referring to rifle cartridges) POLISHING BRASS.... Smooth and uniform case mouths are very important in producing accurate reloads. Therefore, I don't polish my carefully prepared brass in a tumbler. During polishing, the case mouths are hammered against the other cases in the tumbler. The hammering rolls over a small lip or burr on the ID and OD of each case mouth. This peening process also locally work hardens the brass. These tiny rolled-over rings of brass at the case mouths are harder than the rest of the annealed neck. These rings and tiny peen marks are very obvious on new brass. If you look at your nice shiny cleaned cases out of the tumbler, you will see the battered case mouths! I have heard that some people tumble their loaded ammo to clean it and, with a bullet in place, the case mouths would be protected from the hammering. I haven't tried it. CAUTION: There is a serious problem with tumbling loaded ammo. The coating on the powder grains, that controls the burn rate, could be abraded and this would change the powder's characteristics. If you were loading ammo near maximum, after tumbling, you might have created a dangerous pressure problem. I merely wipe each of my reloads clean with a cloth towel to remove all of the grease and dirt. For my "fitted neck" cases, I polish the neck OD and shoulder with a "Krazy" brand polishing cloth (any silver or brass polishing cloth would work) or a bit of Flitz Metal Polish on a cloth before each reload. I swab out the neck ID with a cotton cleaning swab to remove the carbon and dirt. Keeping that case mouth smooth can't be over stressed. FORGET NICKEL-PLATED BRASS.... I liked the looks and feel of nickel-plated cases, but I don't load them anymore and here is why. The cases are strong and it is easy enough to outside neck turn them. That is not the problem. The nickel-plating on the case neck ID is like sandpaper. The only way you might be able to remove this grit is with a case neck ID reamer if you have a "tight neck" chamber and enough neck wall thickness to work with. If you have a loaded nickel-plated round laying around and don't believe me, just pull the bullet. It will look like you pulled it out of a tube of 180 grit wet/dry sandpaper. If you pull the bullet out of a brass case mouth that has been carefully chamfered and polished with the steel wool spinner process above, it will be essentially smooth like out of the bullet box. Want copper in the barrel? Start by sanding the surface of those nice polished precision bullets. Try it with a Moly Coated bullet and it is even worse; the nickel-plated cases scrape off the Moly. The nickel-plated case neck IDs don't get any better after you reload them a few times. They are still like sandpaper. Think about a few of those nickel pieces of grit imbedding into the copper of the bullet and what they do to your rifle barrel! I have heard that the nickel is hard enough to score some reloading dies and also wear down the expander ball.