I've been working on getting my open Glock 19 running and had similar problems to what you are having. Switching to Power Pistol at the maximum that Alliant specs in their manual seemed to get me going and I worked up from there with a plated bullet, and even though I am going to switch to a jacketed bullet this winter the plated bullet worked fine for 2 seasons. Also make sure that the ejection port is lowered to allow the brass an easy path to escape I had to use a trimmed 11# spring for minor pf loads ~150pf and a trimmed 12# spring for Major loads ~170pf, but keep in mind that this was in a shorter Glock 19.
Hope this helps.