Fired primer anvils as brass cleaning media

[mdi]

Tumbling brass is not an exact science. Anything can be used for tumbling and even nothing, no media with brass in a tumbler will work to clean brass. It all depends on the finish left on the case. The speed and finish is what really determines the media. For a quick cleaning, ceramic media, hard resin, BBs, hardware (small nuts and screws) and pebbles will work but the finish is often a dull matte. For a finer finish, softer media (corn cob, walnut, dried peas/beans, cat litter, baking soda) or liquid and small media works.

[Froogal]

If those SS pins are left wet they will rust somewhat, I know this because I've done it

Which also indicates they are not true stainless steel.

[upnorthwis]

There are many types of stainless steel. Some are magnetic, but they're still stainless steel.

[fast ronnie]

If those SS pins are left wet they will rust somewhat, I know this because I've done it

I leave the pins in water in the tumbler with the last little bit of liquid from the tumbling process, so it also has a slight amount of Armorall Wash an Wax. I use a Dillon separator filled with water to separate the pins, so the pins don't see pure water except when I'm refilling to run another batch. I have yet to see any rust.
If you have any steel cases in the batch though, brass does not look too good after tumbling. I have to stop and clean the pins without any brass before I can get good results again. Just my .02

[lightman]

There are many types of stainless steel. Some are magnetic, but they're still stainless steel.

I'm not an expert on stainless steel but this is correct. I have a few different type of stainless bolts in my bolt bins and I want to say that the 300 series stainless is non-magnetic while the 400 series is.

I leave my wet pins in the tumbler drum and have no rust problems. And thankfully mine are magnetic.