On several of my mil-spec 20 rounders I have experianced a failure to lock the bolt back after the last round is fired.  This failure occurs only on certain 20 round mags with alloy followers.  This failure does not occure on my 30 round mags with either the standard black or up-graded green follower.

Upon examination of the allow follower I observed noticeable abbrassions (scratches) on the follower.  The likely cause of these is the bolt coming over the top of the follower.  Is the solution to this problem simply replacing the follower?  If so, are there up-graded commercial followers out there similar to the magpul or the anti-tilt green follower?  

I'd rather not have to take a dremmel tool to anything.  

Thanks in advance,

Gary

How long since you replaced the springs?
I had four really old 20 rounders that wouldn't lock the bolt back. I replaced the springs and they work like a charm now.

To my knowledge, the springs have never been replaced.  These were "pre-ban" mags I bought in the mid 90's as a part of my high capacity magazine preservation plan

I could try a few Wolff spring upgrades and see.

Regards,
Gary