If the cartridge is jamming at the top of the barrel/barrel hood, that usually means the COL is too short. Likewise, if the cartridge jams on the feed ramp, that usually means the COL is too long.
For incomplete chambering (the cartridge got past the feed ramp and attempted to chamber properly), you need a plunk test pretty much at described above.
Take barrel out of gun
Coat the bullet and case with ink from marker (Magic Marker other)
Drop cartridge in barrel and rotate a couple of times. The cartridge will rub the interfering part of the cartridge against the barrel.
1) Marks of bullet mean COL is too long
2) Marks at corner of case mouth and case body indicated the case mouth flare still exists and more crimp is needed.
3) Marks on the case body just below the case mouth would indicate excessive crimping
4) Marks on case body about ¼" above extractor groove indicates the sizing die is not going down far enough and you probably need to Bulge Bust.