If it's a Century Arms build with an Imbel receiver, it can be easily remedied I'd think. Some Imbel receivers were milled for the inch pattern magazine so definitely get some of those. I've seen Century builds on a variety of different upper receivers and quality control was all over the place. I've encountered problems usually from tired parts kits used for the builds like gas cylinders, springs, etc. Nothing to worry about. You just need to go through it and give it a little love.