one on left is original ar-10/sr 25 mag, one on right is shorty ar 10 mag.
sr-25 reciever on left, ar 10 reciever on right.
I guess I have never handled them all so I can't say for sure,
but thats what I have gleaned from the internet anway.
not really important anyway, unless you are going for some sort of frankenbuild
maybe check that the dpms mags feed properly in your AR-10
They do feed properly.