With an extended magazine it might be different result. With standard mags, when you have the slide locked back and slap that thing in there, you are transferring shock directly into the frame.
to clarify none of the 8rd 1911 mags are extended they are all flush fit like a GI spec 7rd mag. And when this happens, the operator is not the one locking the slide back, its the magazine (follower) on the last round fired....