GI Mag Follower Bump

The magazine follower in SA MilSpec magazine I recently purchased has a bump on the follower. I have seen this on numerous MilSpec magazines. It is also shown in the Kuhnhausen 1911 Shop Manual but no explanation of what it’s for. I know it makes loading the first round in the mag a PITA. Most mags seem to work fine without the bump. 

What’s its intended design purpose and why is it added. 

Thanks
Rush

As a round is fed into the chamber, the bump keeps the next round from moving foreword in the magazine.

Actually all rounds in the mag are free to move forward as you say, except for the last round that is against the follower. 

Rush

Round followers don't have the bump

Keeps the last round from dragging should there be a buildup on the follower. Remember these are warfighting implements, designed to perform in all climates. That bump just provides a 1/32" high point contact on the round so that round will still slide out of the magazine.

I have a Colt series 80 that benefits from the bump on the follower.  If I use a magazine without the bump, after the next-to-last cartridge in the magazine is fired, the slide cycles to the rear, the empty case ejects, and the inertia of the slide hitting the rearward stop pulls the pistol to the rear, and the inertia of the last cartridge in the magazine tries to keep it in the same place, drawing it out of the front of the magazine.  The follower then pushes up the slide stop, locking the slide back, and I would find the last cartridge lying loose on top of the follower.  

With a bump on  the follower, it causes the last cartridge to not be pulled out of the magazine.  

Not every 1911-type pistol has this problem with no-bump magazines.