These are the rifles that have the barrel pressed into the receiver. The bolt locking lugs go into a recess in the barrel extension, and lock up in a way similar to that of a semi-automatic. It's a cheaper way to manufacture rifles, to pass the savings on to the consumer. All the tests I,ve read on them said they weren't particularly accurate, at least not like a traditionaly manufactured rifle. From the way they look, if the barrel gets shot out it's a toss away at that point. Cheap build, bad triggers, and injection molded plastic stocks you're not getting much of a gun, but the price probably is it's one redeeming feature.