ETA: I am (fairly) familiar (although not an expert like many here) on the differences in 1:7/1:8/1:9 rifle and carbine barrels for .223/5.56 AR builds. But I have to admit that I have never paid any attention, let alone, learned the difference in twist rates of pistol calibers. Mainly because I never had that option. Could you imagine customizing/changing as much crap on your pistols as you can with your ARs? When I buy pistols, they are what they are. I don't have the option to specify "oh, I want a Glock G17 but I want x length barrel with a 1:n twist rate instead of the factory spec."