Never seen FC with those dot marks, would love to know what it was in the first place. My experience with scrounged pickup Federal (not Gold Medal) has left me thinking Federal from gas guns is really prone to rim tear-offs when FL sizing, plus neck cracking. I got around that by changing my methods, always FL sizing "new used" Federal with the decapper and ball gone from the die so I could punch it out WHEN needed, not if. But after that, and a decent annealing, FC has been fine both as gas-rifle brass and as stock for forming "more" 221 FB brass (which is a pain).
PMC has also been a "good find" or was, when it was plentiful. For the most part, it seems almost any 223 brass can work out just fine if it's given a good prep (including using a pick to feel for the "Base Ring of Doom" plus a weight sort for the "outliers."
