WC with speedloaders is a royal pain in the process. They sorta work if you fiddle them in, but don't expect much "speed in the speedloader."
Speedloads work well with RN, HP and TC. I use HKS for carry and Safariland Comp 3 for competition.
Your model 19 takes a 10A HKS and a Comp 3 S&W K frame, stock #13224 from Dillon (avail many places).