Every time I go to the Starline site to get 10mm it's right there on the line below, calling out to me - 10 MM MAGNUM. I'm thinking it wouldn't be too hard converting a G20 to shoot that cartridge: Get a fully supported aftermarket barrel and drill it out, put on a heavy muzzle break and add stronger spring. The biggest problem as I see would be magazines, there aren't any, yet... I have no gunsmithing, metalurgy or mechanical experience. But for heavens sake, the 460 Rowland bumps the pressure on regular 45's to the double 21K to 40K PSI. That's with AFAIK with standard barrels and slides with a stronger spring and some extra weight. 10mm to 10 mm magnum would only be from 38 to to 43 K PSI. The G20 slide is beefed up compared to a G21 and the barrel has thicker walls - I think... Except for the magazine problem I don't think is too far-fetched, or?