I have some AUG 42 round mags - I was looking at them with a flashlight the other day, and on the spine of the mag, there looked what seem to be hairline cracks up and down the spine.

Are these cracks a just plastic imperfections?

These are kept standing in a chest with a 450 gram silica box. The room is a constant cool temp. Can't figure out what would have cause this.

A lot of my 42 rounders show those same imperfections, the handful of 30 rounders I just looked at don't. I think they are just imperfections from the molding process, IIRC they had them when I bought them years ago. I am not going to worry about mine.

eta: I have some loaded 42rders somewhere else. They have been loaded for at least 3 or 4 years so I will take a look at those a bit later to see if there is anything going on with them.

Ok, I just looked at the two fully loaded 42 rounders mentioned above. Both show the same imperfections shown in your picture but neither of them shows any cracking or other damage. I think it's safe to say it is just part of the manufacturing process and is no big deal.

Thanks for looking at your mags.