Nah. I'd put about ten mags through my G21 and inspect the bore. It usually just had some lube residue that would come clean with a mop. It was certainly cleaner than a regular rifled barrel. Not once did I ever have to run a brush down the barrel to remove leading, because it never did.
Too bad the rest of the gun was junk.
Agreed. I got to the point with mine that I became confident enough to run several hundred rounds through it without checking it. It was always the same thing, no leading. I used just straight wheelweights airdropped and sized to .452 in it. It got way way more lead through it than jacketed. Before I gave it to my son. I concluded that it was junk when compared with any other handgun I had. It was accurate and all but it was finicky with anything besides lead RN. In fairness, it was more accurate than my stockish 1911, it just didn't mesh with my ideals and collection.
The rounds that did jam in it, I would kick to the side and fill an entire mag with them to be ran through my Colt. It was pretty satisfying to have full mags of G21 jammed rounds run like butter through my Colt.