.450 Bushmaster magazines

[ben4372]

Yep. And a guy makes a pop in follower that works great. You just "roll" it in from the top. I bought a few of these when I first got my 450. Its funny, the factory built .450 mags have a dimple or crimp to keep you from pulling the follower and dropping in a .556. These are the ones I bought, I think. https://www.ebay.com/itm/Magazine-Fo...-/152137172696

Almost forgot. I had to cut a crescent relief in the front of the mag, similar to factory ones.

[Little Dutch]

Yep. And a guy makes a pop in follower that works great. You just "roll" it in from the top. I bought a few of these when I first got my 450. Its funny, the factory built .450 mags have a dimple or crimp to keep you from pulling the follower and dropping in a .556. These are the ones I bought, I think. https://www.ebay.com/itm/Magazine-Fo...-/152137172696

Almost forgot. I had to cut a crescent relief in the front of the mag, similar to factory ones.

The followers work well in 20 round metal mags. I didn't cut a relief on them, but did have to gently squeeze the lips together.
I have found that the Hornady Black factory cartridges are actually too long to make the curve in the 30 round steel magazines. I haven't gotten any of my P-Mag magazines to work. They would require some extensive material removal to make work.