Turns out Hexmags are good mags for single stack big bore AR platforms. They do not have the "front alignment ridge" that is there to prevent tilt in normal .223/5.56. This is why most of us have to use GI mags, shave down that ridge in Pmags, or buy dedicated big bore mags. With this follower in the 30 rd hexmag, you can easily get the full 10 rds of .450 BM. I do not have .458 socom, but it should take 10 as well.
SO I modeled this follower from scratch from the original hexmag follower and a set of calipers. The dimesions are perfect, even down to the tapers of the "legs" of the follower. Also made sure to keep width in areas to maintain strength for printing.
I printed upside down with 20% zigzag support in cura, 0.2-0.24 layer heights, 4 walls, 20% infill, 5 top and bottom layers.
Here is my big plug for HORIZONTAL EXPANSION. If you have never adjusted this setting in your slicer, it will revolutionize the accuracy of your print dimensions. Definitely look into this if you never have.
Horizontal expansion will be the reason someone will say that a model is "too large." Yes, you can scale it down, but that changes dimesions and isn't the right solution to the problem. SO, if you print this and it is "too large," I encourage you to look into your printer settings. It will make ALL of your parts fit the way they should.