Re: using mercury to remove lead- yes, it works- and we USED to do it here. However, since mercury is very poisonous, it is very difficult to get it here. With a 22, bronze brush and bore solvent takes care of most problems. For .357 Magnum, I use a Lewis De-Leader. Brass screen over a leather plug that fits the bore very tight. Have pulled CHUNKS of lead out out the bore after shooting a LOT of lead wadcutter bullets.
What we have heah is.... failure to communicate.