Thread: Whats this for

Hard to tell from the picture angle, my ERA bolt will "slide over" but I always clip the round into the follower to be sure ..... I mean to say these are old rifles and you need to be a bit gentle with them! This rifle has had the follwer ground back so that it doesnt stay locked open.
The Winchester one is the same, looking at them there is a little bevel to the extractor ( on the edge not visible in your photo @raydafish ) so that might be allowing the round to slide under the extractor without causing trauma, hope that helps.

I had been led to believe that the device shown is a single round adapter too. But as I say I always clip the rim into the mag even for single shot shooting.