Never shot the fmj, but shot ACC's for years. ACCs were the flip-side of FMJ...(Alum inside, carbon outside), so they would be similar. I loved acc's, very forgiving, quiet, small diameter, and shot a wide-range of bow weights/types well. My 3-49's shot well from 45#-55# recurves and up to 60# compounds with 150 grains up front (50 gr outsert + 125 gr BH).
There are some 3-60's in the classifieds at 28" fletched. I shot this spine in 55# recurve with 125-150 upfront and also in 60-65# compound. Most shafts took 2-3 deer each before it hit a rock in the ground after full penetration.
3-39 are .440 spine,
3-49 are .390 spine
3-60 are .340 spine
I expect the FMJs to be as good.