Vinegar and Hydrogen Peroxide makes lead Acetate? By golly, you have done what philosphers ages ago failed at. The transmutation of metals!. Now, if you can move up the periodic table just a little, you can turn lemon juice and water into Gold!.
Has anyone tried either of these two methods?
Go to a dive shop and figure out how to seal either the breech or muzzle to their air compressor. They regularly fill SCUBA tanks to 3,000 psi.
Dive shops that pressure test tanks fill them with water and run them up higher than that. (If the tank fails, you don't have an air "bomb", the air tank just cracks and the water begins to leak out.
(I suppose brickeye's method would be easier, but I don't think CO2 has more than 3,000 psi, but I may be wrong)
In muzzleloading days, (if the method in JimK's post 49 did not work or it still gives you the willies even after his testimonial) I am told it was common to have a cleaning rod fitted with a tap (not a lot different from a wood screw). A stuck bullet could be grabbed by the tap and then pulled out. Just make sure the tap does not scratch your rifling. Easy if you use a bushing as a guide.
If worse came to worst, you could stick a drill bit into the center of a rod and make a hole in the bullet, Then enlarge the hole until there is just a thin ring of lead inside the barrel. Then clean the lead "fouling" out like you would after a shooting session.