Gunner Gatlin, SASS 10274L

Howdy - been enjoying going through the teething pains with my 550C purchased a number of months ago. The thing overall works great - but there is a small issue that can create big problems. My spent primer chute stays open as I raise the shell plate. Have played around with the cotter pin, but that seems to work through maybe 5-10 cycles at best. Any solutions to keep the the chute closed during depriming and working properly? GG ~