ANY kind of slug can be used in a rifled bore. However, it is POSSIBLE that the Foster type and the old style Brennekes might cause leading. This happens in some barrels, but not all of them....

I believe there's something weird about a sales clerk in a store who won't sell you what you want! Even if the slugs would ruin the bore in 10 rounds (B.S.)!! it's YOUR BORE!! "Let me speak to your supervisor, please!" You might get leading. But I've never experienced leading in a shotgun bore that I could not clean out with Shooter's Choice or one of the other good bore solvents.