I recently purchased two twenty round mags from a co-worker who got them from his dad.  The father was in 'Nam and had these mags for a while.  When I took them to the range I found I could only load 5 rounds in one of the mags.  When I first got the mags I took them apart and cleaned them but paid no attention to a small strip of metal "banding" that went around the spring on one of them. After I removed it I could get 20 rnds in the mag.  Both are Colt mags and I was wondering if this is a factory item or if it was an aftermarket item.   The 5 rnd mag did not say it was a 5 rnd'er on the floorplate.  This strip of metal is a U-shape and the ends are bent on the corners.  Has anyone ever run across anything like this?

A square U shape with the corners on each open end bent in??  If so this is/was a Colt 5 round block that they put in 20 round mags.  Back in 1976 when I got my first AR , I ran into these in the mags.

I was given a Colt 20 round mag and it had one of these blocks in it.  I still have the block, but have no use for it.  What to do with it?  

I will buy it, how much do you want for this part? (obviously for a reasonable amount!)

Fire me an email so that we can discuss, thanks.

Thanks for the help.  I think I'll hold on to it may want to hunt with it someday and I'm a pack rat, I don't throw anything away or sell much gun related stuff. Maybe that explains all the clutter around the house.

I've got one of the blocks that came from a Colt 20 rounder if anyone wants it. Shoot me an IM.

-Charging Handle

I have two of these as well. But would removing the block constitute the manufacturing of post-ban high-cap? or because they were made before the ban, Legal?