460 Rowland
I have a a 460 conversion from Rowland for my Glock 21. Even though it was more money I felt with the high power, I would go to the experts who originally developed and made it. Kit comes with the comp and 24lb spring. I also bought 2 of the heavier mag spring and a box of 185gr Nosler HP's from them. Originally I bought a complete Glock 20 in 10mm. Then had a chance to pick up a complete Glock 21 upper. Since they share the same frame I can just switch the uppers around. Have not shot yet, frame is at Robar getting a grip reduction.
Will report on once I have had an oportunity to shoot.