I don't think the guide rod or recoil spring can have much effect on how a round chambers (or doesn't) UNLESS the recoil spring is really weak -- and that wouldn't cause nose-dives. It just wouldn't have stored force to strip and fully chamber the round. If the existing guide rod and recoil spring feed other rounds properly, you can probably discount both of those variables.
I've found that shooting 9mm hollowpoints in my FNS-40 semi-auto (when running a 9mm conversion barrel) will cause the hollowpoint to bite into the feed ramp, while hardball (round nose, no opening) feeds regularly. (I ended up buying some 9mm mags -- even though I'd almost never shoot hollow-point ammo n the conversion barrel.) I don't think that would be a problem if I were running the same round in a 9mm gun, rather than a converted .40. And since it's still happening with a new mag, it's arguably not a mag spring issue, or that you might be using a mag for the wrong caliber. (Weak mag springs will often still work if you download 3-4 rounds -- but they can't handle the extra weight of a full mag.)
Weak springs often cause the nose of rounds to dip -- but if they do, they'll typically do it with all rounds of any shape, not just one type -- but do it less often if you download several rounds.
It may just be bullet shape.