Dear Friends, Hello again. I am back to square one. In my last post I told you that the gun cycled the 71/2 shells. So I assumed the gun is fixed. However when I went back to the same range and asked the owner to let me try a couple of slugs. He was kind enough to try a couple of slugs and shot the gun himself. Same problem the gun did not cycle. so the gun cycles 71/2 but not slugs. Both shells are 12 gauge 23/4 inch and 1 OZ. So may be i was confused, about the assembly. May it was assembled correctly all along. The problem is now narrowed to the type of shell. It just does not cycle slugs. I read online that some of these guns come with two pistons, light load and heavy load. mine came with just one piston. May be I need to try a heavy load gas piston. Do you know where they may sell shotgun gas pistons?