No, I use plastic wads like everyone else. They don't completely contain the shot charge, there is plenty of lead contact with the bore.
The pits Drew observes are in guns that could not have seen a plastic wad until the 1960's.
Undoubtedly the actual corrosion was caused by salts left behind by the older primers, but once a pit starts and gets covered over with a coating of lead it's hard to get clean. It's a little galvanic cell that keeps turning iron into oxides.
I did used to load 20 gauge spread loads with BPI X inserts and WWAA20 wads with the shot cups trimmed off so the X wad would fit. I didn't have a serious problem with them until I loaded a couple boxes for a friend with a Model 23. The lead was deposited in his barrels in sheets. The leading was so bad, I was afraid it would act as an obstruction. I no longer load those! That was 6% Sb Remington shot by the way, not some cheap crap.
