[moooose102]

i usually polish the heck out of my brass until it glows. but now, i want to actually stain some of it for a particular reason. is there a way to permanantly stain brass so that it will not come off during tumbleing?

[janobles14]

straight vinegar soak will patina the crap out of it but i think it would do some bad juju. also copper killer (bore cleaner) will turn it dark brown but again might pit and damage.

[Otto]

...is there a way to permanantly stain brass so that it will not come off during tumbleing?

No not really, the finish will eventually wear off.
Brass Black is used to mark and identify cases and is easily re-applied.
http://www.cheaperthandirt.com/ctd_images/lgprod/23451.jpg

[The Bushmaster]

Grape kool-aid...

[jmorris]

Put them in black soil and get them wet (rain seems to work pretty well).