Ammonia can turn the brass brittle, which obviously isn't good for containing small explosions! "Probably" won't hurt it immediately, but most reload their brass several times. Why chance it when there are other products out there. Try a SMALL amount of NuFinish auto wax, or get some Hornady One Shot. I've found the NuFinish can leave a film on the brass once the media get loaded up with it. I ended up trashing a whole batch and went with a mix of ceramic media and regular corncob/walnut shells.
If you don't want to tumble, try washing the brass in water and washing soda (NOT baking soda). Get the soda in the laundry section. I may even use a smidgen of regular soap. You can let it soak for awhile, but DO NOT soak for hours as the brass will tarnish. You may still get some tarnish, which is still OK to a point. After rinsing WELL, leave a bit of fresh water covering the brass and then dose it with a bit of regular vinegar. Swish it around and the brass will immediately brighten up. Don't soak it in the vinegar, just swirl for a minute and then rinse well and dry.
I sometimes go through this washing routine even when I tumble. Keeps most of the crud out of your media.
A forum community dedicated to Springfield Armory XD and XD-M series firearm owners and enthusiasts. Come join the discussion about optics, gunsmithing, styles, reviews, accessories, classifieds, and more!