I am very confused about all the diff. types of 38 ammo out there.
I'll try and do a quick rundown.
.38 Long Colt uses a 1.03"-long case and an inside-lubricated .357"-caliber bullet. The most common loading is a 140gr lead round-nose bullet. Most older Colt revolvers simply marked ".38" are chambered for this cartridge.
.38 S&W Special, usually known simply as .38 Special, is a higher-powered derivative of .38LC with a lengthened 1.16" case. .38LC handloads can be made from trimmed .38Spl cases, and .38Spl revolvers can safely fire .38LC, but .38Spl ammo
should not be fired in a .38LC revolver due to its higher operating pressure.
.38S&W, .38 Colt New Police, .38 Police, .38NP, and .38/200 are all the same thing, depending on the cartridge maker, gunmaker, and military user. This cartridge was widely used in top-break revolvers from a bewildering variety of gunmakers, along with twist-open Merwin Hulberts* and small-frame swing-out cylinder revolvers from Colt and S&W. It has a 0.78"-long case and a 0.361"-caliber bullet. The case also has a slight taper, unlike .38LC and .38Spl.
This cartridge will fit in some .38LC and .38Spl revolvers with unusually sloppy chamber dimensions, but this practice generally isn't recommended. FWIW most commercial loadings use soft lead bullets that can safely be fired through 0.357"-caliber barrels- in fact, S&W reportedly used such barrels on some postwar .38S&W revolvers to simplify parts inventories- but firing
military FMJ .38S&W or .38/200 ammo through a 0.357"-caliber barrel
should not be attempted. FMJ bullets will not "snug down" into the sub-caliber barrel as readily as lead bullets and an over-pressure condition (and catastrophic kB!) may result.
.38 Short Colt is similar to .38LC but uses a true .38"-caliber outside-lubricated heeled bullet, i.e. the outside of the bullet is the same diameter as the case, like .22LR. Since the bullet is so much larger than a .38LC or .38S&W barrel, the above warning about overpressure applies; firing this cartridge through any other .38-caliber revolver
should not be attempted. However, .38SC is pretty much an obsolete historical footnote today.
.38 ACP (aka .38 Auto) and
.38 Super (aka Super .38 or .38 Super Auto) are Browning-designed automatic pistol cartridges that are totally incompatible with all of the above.
OK, so maybe that wasn't so quick.
*Footnote: A small quantity of .38S&W ammo was produced in the late 19th century branded as ".38 Merwin Hulbert". Although this ammo can be safely fired in any .38S&W firearm, this practice isn't wise because MH-branded cartridges have become somewhat of a Holy Grail to vintage cartridge collectors. Single cartridges have been sold for over $50 and an entire box will fund the purchase of a nice new gun or a Mediterranean cruise.