I have been using 1 part white vinegar 1 part Peroxide for years on stainless barrels. I don't have to leave it soak for "hours." 10 minutes usually does the trick. The lead gets gummy and releases from the barrel. I do understand that the remaining compound is a health hazard. Just a few more points- I have been told that it will remove bluing (I have never tried it in a blued gun). Don't premix the peroxide and vinegar. Mix only what you want to use that day. Apparently the mix loses it's potency. I have also soaked heavily soiled cylinders in a batch of the mix. It works great to remove lead from the face of the cylinder.
Mark