Based on the concerns listed by the OP in all three of his "not enough rounds" threads, I would have to suggest that he give up on his goal of carrying a revolver as a primary weapon and choose a semi-auto with sufficient capacity to make him feel comfortable in his ability to fend off 5 armed attackers.
The Glock 21 is a fine firearm if you want a high-capacity .45, and then there's also the Glock 17 if you want a full 18 rounds before reloading. As mentioned earlier, there is a 32-round mag available for the Glock 17 which you could carry as a spare in case you exhaust the first 18 rounds and still need to keep shooting.
You might also want to look into similar offerings in the S&W M&P, Ruger SR, and Springfield XD families. All offer rather high-capacity magazines in the full-sized pistols.
Basically - if you feel you are undergunned with an 8-round revolver, then it's really not the right platform for you.
I most often carry a 5-shot J-frame revolver if I carry at all. When I was a police officer for 15 years I carried a 6-shot K-frame revolver. Turns out that was 6 shots more than I ever needed.