The FC cases are heavy, and thick... and softer than brass from other makers. You'll see pressure signs sooner, even with reduced loads.
What ends up happening is the neck tension begins to vary too much from one case to the next with the FC cases. You'll seat one bullet, and it's snug... the next bullet almost falls in, even though both cases were sized the exact same way.
I haven't examined any of the FGMM ammo lately, but they may (MAY) be using a slight crimp on the case necks to even out neck tension to some degree, plus when the brass hasn't yet been fired, neck tension is going to be more uniform--most likely.
For the .308, the Winchester brass really works well. Lapua is of course better, and IMI (if you can find it) is every bit as good as Lapua. I don't like Norma cases, for the same reason I don't like the FC cases... heavy, smaller volume, not as tough.
All I can tell you is what has--and has not--worked for me. As they say, your mileage may vary.