I have shot my homegrown cast slugs in my stock G21 SF barrel before I got a Lone Wolf 6" barrel. I was very careful to clean the bore after every range session so no build up of lead would have a KB to occur. But, we were talking speeds of less than 1000fps. Not, 10mm velocity with speeds of near 1200fps with a LEE SWC 175gr. slug lubed with Liquid Alox. WW will be my casting alloy by the way, water quenched right from the mold. Anybody doing this with their stock barrels in 10mm stock barrels, safely? I'll be getting an aftermarket barrel soon, just wanted to see if could do for this for a while until I can alot the funds for the new barrel. Thanks!