I have a lifter from an original 73 Circa 1889 that has a slot of about 3/16 in deep in the sides of the lifter so that
only about 1/8 in at the front and back slide on the receiver wall. I believe that it came from the factory this way.
That would be a .32-20 carrier. The big bores didn't have the slot. None of the Ubertis come this way. from the factory.