Amend 2 Mag Bulge Problem

[KZero]

So, I’m about to be in the market for Grendel mags. Why is polymer preferred to metal? I run metal 5.56 mags in my other ARs.

When it comes to the Grendel, I don't think it can be said there is a preference for polymer magazines; as far as I know, the Amend2 are the only ones currently available, but I'm new to the cartridge and could be wrong.
Much like you (I suspect,) I went looking for a consensus on which magazine(s) were best to invest in. So far, I've found it to be anything but a settled issue.
The best I've found is that the CProducts and ACS are a decent gamble, though I've found plenty of posts where both have needed some fiddling to work correctly.
Amend2 are new to the scene, and so far it seems to have complaints about how hard some people find them to load, and that they can bulge if left loaded for more time than it takes to shoot them empty.
I have three of the Amend2 examples; I've not yet tested them for bulging, but I don't find them the least bit difficult to load to capacity. I took and posted some pics on it, and at least one someone has a video out on YouTube that does a good job showing how.
I also have one example each of the CProducts and ACS, both are 5-rounders. I can't say which of any of them is better; I'm still waiting for all my parts to get here for the rifle.
It may be a moot point right now anyway; when I ordered mine, there wasn't a large availability of any of them except the Amend2.