I ran some Aguila and PMC, which I think are "lighter" loads, with the original spring and it ran fine. Still tossing casings but I just moved the tarp! I worked the slide stop slightly and lock back was fine with McCormick mags. As you can see I'm still getting used to the trigger. Surprised it's that different from my Guardian. Not like it's bad or anything just different, maybe the long trigger vs. the shorter one on the Guardian.