There is an old myth that if you shoot a lot of lead bullets and get your barrel leaded up, you need to shoot some high velocity jacketed bullets through the barrel to clean out that lead fouling.
Doesn't happen. Actually you can compound the problem by shooting jacketed bullets through a lead fouled barrel. What happens is the copper jacketed bullets do not push out the lead as most everyone thinks it does. It actually runs over the lead fouling and presses it down into the pores of the barrel steel. Now you really have a problem. You also have covered up the lead fouling with copper fouling. Two dissimilar metals do not get along well and can cause pitting. If you shoot a lot and get the barrel heated up you can almost solder the lead to the barrel. Good luck getting it out then. Also you know have to use two different types of barrel cleaner. One to get rid of the copper and then one to get the lead out of the pores of the metal. Twice as much barrel cleaning time for your efforts. Don't do it.
Just clean the barrel with a good bronze brush and solvent (what ever you usually use). It will creep under the lead through the scratches your cleaning brush makes when you scrub it bore. Then let it sit a while until the lead is loosened and use patches to clean it out.
But don't combine copper jackets with lead cast bullets.