Quote Originally Posted by Justin View Post
I looked at one of those awhile back. The problem with them is that the magazine blocks usually lock into the mag well via the standard AR magazine release, and the block itself has a magazine release similar to the paddle release on an AK.

The problem with this is that if you're used to hitting the traditional magazine release on your AR and you do this while the block is in, you'll dump the magazine and the block on the ground. If you want to keep the same manual of arms on a 9mm conversion as on a regular AR, you're better off going with a dedicated lower or something like this magazine conversion which seems like a really clever idea..
Go over to calguns and pick up a bullet button mag release.