Part of your problem sounds like a headspace issue. The extractor is not supposed to hold the rim of the cartridge for the firing pin to hit the primer. The shoulder of the case is what is supposed to determine how far the cartridge fits/slides into the chamber.
Your comment that "put a shell in it and it let the shell go into the chamber well below flush of it, unlike the 223 that stayed out of the chamber a little ways." idicates that you have sized your brass too much.
Since the firing pin did dent the primer, although slightly, sounds like the locking lug was working correctly on that frame, but your cartridges aren't headspacing properly.
Try sizing your brass so that the action just closes on a sized case. Do this by backing out your sizing die, sizing a case, and trying it in the chamber. If the action won't close, screw in the sizing die 1/8 of a turn, resize and try again. Repeat until the action just closes on a sized case.
Then check for function by priming the case and trying to fire a live primer. Of course treat as a loaded round, keep gun pointed downrange, ear protection, etc. If the primer fires, then you will know that the problem was a headspace problem.
Hope this helps.
Brad