I bought 2 Colt 5-round magazines off the EE.  I took them to the range yesterday only to find out they hold 6 rounds.  The first 5 went in no problem as usual and to my surprise the 6th round was no harder than the previous five.  I tried to put a seventh one in but it wouldn't take it.  I bought these 5 rounders for hunting in Michigan where it states that a magazine and chamber cannot hold more than 6 rounds combined.  Now I'm in a predicament having 6 rounds in the magazine plus 1 in the chamber.

First, is something wrong with the mag or did Colt mistakenly make them 6?  Second, how can I modify the mag by adding a plug or otherwise to make it 5 rounds.  And lastly, is it legal to plug the mag this way to use it for hutning.  I assume it is since you can plug the magazine tube on a shotgun to use it for hunting.

Do you have a pic of the mag?  Does it look like the colt 20rd. ones?  I bought one at a show, thinking it was a 20.  Turns out it was a 5...with a rivet in the floor plate and an insert in the body so it'd only hold 5 rounds.  

I dremeled off the rivet, pulled out the insert, and turned it into a 20.
Just wondering if you have the same mag.  I've seen 5rd. ONLY mags, not sure where though.

Here are some pics of my 5 round mag
20 round USGI mag body
block intalled inside, with rivet in floorplate

(it only holds five rounds, no way i could get 6 in there)

http://i3.photobucket.com/albums/y74/zaq12wsx/DSC_0153aaaaaa.jpg
http://i3.photobucket.com/albums/y74/zaq12wsx/DSC_0154.jpg
http://i3.photobucket.com/albums/y74/zaq12wsx/DSC_0155aaaaaa.jpg

I'll take a picture of mine tonight after work and post it.  It's really small, not just a 10 or 20 rounder blocked.  It doesn't even stick out of the magwell when inserted.  It actually seems pretty poor quality as the floor plate easily slides off and the notch in the front of the plate won't slide all the way over the front.  I'll post pics later to show what I mean though.

They make 9 rounders too. The modification should work to turn it into a hunting-legal 5-rounder.