Its a g20. I wanted a fully supported barrel to minimize bulging brass with hot loads. I havn't ever had a feed problem with it.Is your kkm barrel the conversion version for a g21 or do you have a g20 and wanted a tighter fit? I've read that the g20 is a heavier slide.
There are alot guys are putting after market 10mm barrels in the g21, and I havn't heard of any failures. Some guys also change to a 20 or 22lb guid rod spring.