In no specific order, nosedive jams can be caused by:

1. Shooter error (limp wrist)
2. Dirty or unlubed gun
3. Magazine issues (misshapen feed lips or weak mag spring, or even a too strong mag spring)
4. Weak recoil spring
5. Underpowered ammo
6. Feed ramp/bullet nose shape incompatibility
7. Too strong recoil spring

If it makes it up as far as the extractor, it isn't really a nosedive jam.