Grendel mags?

[stanc]

Why is wall thickness even an issue? Couldn't you just keep the thickness the same and adjust the stack width by increasing magazine length? It just be a longer magazine with a narrower stack. Why wouldn't that work?

I think a "proper" double stack is necessary for two reasons:

(1) to keep magazine length to a minimum; and (2) to correctly align the top rounds with the barrel feed ramps.

What you propose would result in a significantly longer and heavier magazine, and because of the reduced stack width, it might not permit reliable chambering.