personally, i use __________, but it really doesn't matter.
as per danjet500's advice, and others before him, ammonia is what eats the copper up. if your flavor has ammonia, it'll work.
A WARNING TO THOSE WITH CHROME LINED MILITARY OR PRIVATELY LINED BORES...
DO NOT LEAVE AMMONIA IN THESE FOR LONGER THAN IT TAKES TO CLEAN THE BORE.
IT WILL ATTACK THE CHROME LINING ALSO.
an FFL who dealt out of his house in this area used to shoot 1911 competitively at camp perry for about 10 years. back when he did so, lead bullets were all they used. he kept a jar of mercury to soak the bbl in overnight, and after letting it hang an hour or so to let the excess drain back into the jar, he'd run a brush through it. really works, and much easier on the rifling.
keep the brush wrapped up in plastic, or in a jar as a designated mercury brush. wear gloves when handling mercury. spray bbl with cleaning agent over a container to catch remaining mercury. shoot first round UPWIND from firearm at next outing, NOT indoors. application of heat to mercury will make it airborne, and easily inhaled.
READ THIS COMPLETELY BEFORE MESSING WITH MERCURY, IT IS A VERY HAZARDOUS METAL:
http://www.ehs.gatech.edu/Mercury and Compounds.pdf
gunnie