Back in the mid 70s when they went to the Satinslide bolt guide they broached a slot for the lug guide to run in through the receiver. It went all the way through the ring which wasn't strictly necessary, but was cheaper. The upshot of that was some of the rings came apart when a case seperated on firing. If they've done away with that, you may be right. Mine is one of the very early ones made in 1959, and has managed to avoid the extractor problems that led to the redesign in '64, or '68 whenever.