I believe that if I do it won't be with a Glock slide. I will definitely get an aftermarket slide since they are made to improve the characteristics of the Glock slide. The LWD and Caspian slides advertise their Rockwell hardness, where Glock does not. Although, from what I saw on the Caspian web site, they don't offer a G21 slide.
I'm not going to give up on .460 Rowland. But I am going to be a lot more cautious with how I go about it.
Here's another pic that looks more like OD Green.