Just about every question about cycling has already been answered in this thread. How many rounds through your S12 so far? What exact loads/brands did you try? Which gas setting(s) have you tried? Do you still use the stock gas regulator? Have you checked the patency and number of gas ports? Their size? Did you try firing the gun prior to converting it? Did it cycle at all beforehand? Do you 'limp wrist' the gun (not lock it up tightly against your shoulder)? Is the gun lubed up well? More specific answers might be available once this info is posted. Welcome to the forum and hope your predicament gets squared away.