Well Blackwolfe, I'm new to this also but I have read everything I could find for the last couple of months. And from what I have seen, all of the 30 round mags are curved to allow for the taper of the cartridge. The 20's can be either curved or straight. In the straight 20's you can see that the base is angled to allow for the taper. Either one works well, I think it is a matter of preference. I have chosen the 20 round stainless steel mags (which only come straight). If the worst happens tomorrow, (election day) the mags I have might be all I can get and I chose the SS for it's long term durability. I also have some Pmags coming and those are straight 20's also. The aluminum mags are considered expendable by the army and I have heard people say don't worry about the aluminum mags, if one messes up, just pitch it. That may be fine if you have 30 magazines, but when you only have a few, I want to keep all I have! I hope this helps a little. 44 Man