Glock does not like cast boolits, hard or soft, regardless of caliber. If you shoot cast boolits in a Glock-only, GSSF match, you will get no re-shoots for any reason (don't ask how I know). A friend loaded his 19 with hand-cast boolits for USPSA and, at one point, something went wrong and blew the slide open and the magazine out the bottom. This was 20+ years ago, and I don't recall the exact cause, but most of us reasoned that it was his rather sloppy casting/loading technique. I shot cast bullets in .45ACP in a 21, 500 rounds a week for years with no ill effects. Another friend shoots his 21 with only cast bullets since at least 1993, an A-Class USPSA shooter. Thousands and thousands of rounds. It is also his EDC, and he is one 70 year old guy you don't want to shoot against. (But, heck, he can't be THAT good. In a twelve-gun bowling pin match he only came in first ahead of me by .02 seconds. .02 seconds! Never should have let him borrow my lever gun...). I don't know that there was anything special about the 10mm. Another guy in that same club used a Glock 10mm to shoot the pants off just about anyone, with cast bullets all the way. Very probably still does.