Purpose of case clipping primer slide angle lever #48?

[rangedog]

I'm wondering why the case, after priming and during indexing, clips the leading edge of the angle lever and moves it in and out a liittle?
Am I missing something obvious?
Is it to create a little tension to index against?

[LeupoldMRK4]

That seems to be a safety device so you cant run the press in reverse possibly causing a double charge. 

[rbwillnj]

It also prevents you from advancing the shell plate if you are out of primers because the end of the primer follower drops into the primer slide and prevents the angle lever from moving.

[Rolling Stone]

That is what I thought too. The follower really locks things up. If you are not out of primers you can always move the lever to back up, but not when the follower is in the primer slide. Sometimes still causes an anxious moment, when I fear something else has fubar-d before I look at the tattle tale (marker) on the follower.
RS

[rangedog]

Makes sense, thanks fellas 

[Jep]

It also jiggles the primer slide to allow better seating of the primer in the slide.
Jep

[llwsgn]

so much attention to detail in these old machines, so much i'm learning as i lurk about in this place.