Oh boy! What really removes Lead fouling from gun barrels easily? Yes there is a substance that does it without scrubbing or any sort of effort but there is always a but isnt there. Before the health safety and joy police managed to snatch more power from us unsuspecting folks and beat us over the head at every opportunity they can, the traditional way in the gun trade here was liquid MERCURY! Gasp stagger back in horror!! Thoughts of mad hatters and rather sick people in the Mercury Gilding trade. That said just cork the muzzle pour in about a quarter of a pound of the fascinating silver toxic stuff in the shotgun bore then cork the chamber then roll it from breech to muzzle takes about one minute, all the lead is gone.
As they say over this side of the pond Ya pays your money and takes your chance I am still here and have done this for more years than I care to remember.