I converted my 21c to .460 Rowland. I had no other use for it since I carry a Glock 29 10mm anyways. It’s a beast. I posted some velocity/energy data in this thread if you care to check it out. I love the Glock 21 in .45 acp and have gone through about 4 of them. It was hard for me to tamper with perfection. If it was my only handgun, I wouldn’t have done it... but it wasn’t. expansion of a 230 grain JHP at around 1200-1300 fps is pretty incredible. penetration is extreme also. The .45 super conversion is pretty awesome too. It doesn’t require anything more than a new recoil spring and guide rod and you will be making a lot more energy than .45 acp and your Glock 21 will take it like a champ since it was originally designed around the 10mm automatic cartridge which operates at a significantly higher pressure than the .45 super.
A buddy of mine just converted his 1911 to .460 Rowland, haven’t had a chance to play with it yet...we’re supposed to hit the range sometime next week.
The data for that round is pretty impressive; over 900 ft lbs...wow :)