Please take this as constructive criticism. You are using terms that are not sufficiently descriptive to explain your problem.
A "bullet" is the projectile that goes out of the barrel.
The "case" is the brass part into which the bullet is inserted.
The "cartridge" is the complete round.
The term "shell" can mean either the case or the cartridge, depending on who's talking. Since it's imprecise, it's not a good idea to use this term in these kinds of discussions.
Having said that, you can refer to bullet length, case length, or overall cartridge length. Cartridge length is often abbreviated as OAL (overall length), COAL (cartridge overall length), or COL (same thing).
If you could re-work your question using these commonly understood terms you will have a better chance of getting meaningful responses.
If you want to shoot...shoot...don't talk! Tuco
USAF Munitions 1969-1992