Before you get all excited and wet your panties, I need to publish my DISCLAIMER.
TAPCO and ProMag magazines with the G3/1 and G5/1 adapters ONLY:
IF you have NOT done the "drop free" bolt mod this will NOT APPLY to you. If you have, please read below.
If you have "shaved" your bolt so it will allow the removal of the Tapco or ProMag magazines, with the bolt closed, you need to know this PRIOR to buying the adapter.
When loading a mag with the bolt closed it may not load correctly. It probably WON'T want to load with an odd number of rounds in the mag without taking additional material off the side of the bolt on that odd side. You MAY need to do the even side also.
This is easily resolved by removing some additional material from the sides of the bolt ONLY where the front of the round rides against the bolt. Remove material a little at a time, at a 45 degree angle and check for fit often. See the pix on the top.
You only want to remove enough material for the front of the bullet to "clear" the bolt on the "rock-n-lock" process. The tip of the bullet MAY hit the bottom of the bolt and "roll" out of the mag as the loading angle has become steeper. With the duckbill removed the mag locks with a much sharper approach angle. Removing some additional material from the bolt allows the bullet tip to clear the bottom of the bolt.
It is most easily done using a Dremel tool and the sanding drum attachment. Remove the extractor so you don't grind on it. Go slow, take your time, and refit often to check your work.
Time spent doing this will help in the adjustment process later.