I actually used a drill bit to make the final "cut" to connect my cuts inside the magazine on the front face to the top. This helped keep some of shape of the bevel inside the feed lips. Again a dremel would've made this much easier.
All cut out.
I also used a chisel and an exacto knife to try and cut in as much of the bevel as I could on the extended portion of the feed lips. No picks, but after you cut it out, there's no bevel so it holds the round lower in the mag until you fix that. Mine still feeds with minimal beveling.
At this point it's just a matter of filling in the void at the back to whatever COAL you want. My first attempt was slightly too small and the plastic on top overhung my spacer block. This was fixed with a file in about 10 seconds to bring them flush. I also put the cutout piece behind it to push it out forward slightly.
I partially reassembled the mag and did a test with some dummy rounds I had. They would feed but now there is ~.3" gap behind the follower so if it slides back at all then the rounds will jam in the mag.
To at least prove that the above is the issue, I drilled 2 small holes in the back of the follower and stuck a nail in each one as a spacer to keep the follower from rocking back.
This works but the nails do rotate slightly and will occasionally bind on the wood. This got me to 90% functionality though and is how I have it setup now.
To improve this I'd do the following.
1 - Only increase the OAL just above what's needed, this would eliminate the follower rocking issue I had.
2 - Use something other than wood in the back (I'll grab a piece of the plywood cap that the guy on 24 hour campfire used when I'm at HD next time I'm there). If I used something harder/smoother I think it'd eliminate the nail heads binding.
3 - Epoxy the base of the nails into the follower (I didn't do this because I will likely push the spacer out further and shorten the COAL in hopes that it brings the follower rocking to an okay level.
4 - Use a dremel.
5 - I'm considering trying this but am not sure I want to cut it further, I could take the follower from my .308 Tikka mag and just use that.
I’ll write this up over the weekend… after talking to MT and learning they are a ways out on their .223 mags I got to work on my factory mag with a jigsaw bit, a file, a chisel, a drill, and some sandpaper. I also used a scrap sheet of plywood, 2 nails and some electrical tape.
