I'm adding this to my personal bookmarks this morning. I have been plugging in sectional densities and the .357 Magnum is amazing me so far.
http://www.beartoothbullets.com/rescources/index.htm
10mm 220gr Hardcast SD = .196
.357 200gr Hardcast SD = .224
.44 300gr Hardcast SD = .232
.45ACP 230 Hardcast SD = .161 :-X
Pretty amazing the little .357 round is almost equal to the .44 packing 100gr more.
Yes, the SD is a relationship of length to diameter...the longer bullet is better stabilized as it spins.
The 44 and 357 as revolver cartridges, they can have more bullet outside the casing only limited by the cylinder's length. The action on some lever rifles are too short to cycle long loaded projectiles. That is what happened with the RCBS 180gr Silhouette bullets I cast, to use them in the lever gun I need to adjust the loaded length shorter to have them cycle and same in some revolvers with short cylinders.
The semiauto bullets, like the 10mm, tend to be shorter to keep the enough space in the casing for powder and the cartridge short enough to fit in a reasonably sized grip profile!