[glassman]

I'm obviously a NOOB. I went to the thread by pax at 'corneredcat' but the difference still eludes me.

[Baba Louie]

The original .45 Colt was a blackpowder round used in Colt Single Actions circa 1873.
The .45 acp (auto colt pistol) was a smaller updated design utilizing smokeless powder matching the earlier round's ballistics. Besides being shorter in length, rim is different as well due to extraction capabilities in a semi-auto design vs revolver.

[runfrumu]

Someone correct me if I'm wrong, and I'm sure I am. The .45 colt casing is longer than the 45.acp but the ballistic's are about the same, being that the acp has a newer powder than can pack the same punch with less. The .45gap is shorter still than the acp, with as good or better (so I've been told) balistic's than the acp.

Theres a general idea at least.

[Smith357]

The .45 Colt (often incorrectly called the .45 Long Colt), was introduced in the single action Colt revolver in 1873. Two years later, it was adopted by the U.S. Army and served there until it was replaced by the less powerful .38 Long Colt in 1892. Originally loaded with a 255 grain lead bullet pushed out the muzzle at 810 fps by 40 grains of black powder, the big cartridge generated a then impressive muzzle energy of 378 foot pounds. Today, Colt's .45 caliber cartridge is loaded with smokeless powder to a nominal muzzle velocity of 855 fps with 250 and 255 grain bullets and a 225 grain bullet at 900 fps.

During its heyday, the .45 Colt was the magnum of revolver cartridges. Only the .44 Special with its 360 foot pounds of energy came close to matching its punch. Even though the various modern day magnums have pushed the old 45 to the bottom of the performance charts, it still has enough life left to be used for hunting game up to whitetails in size at woods ranges. A 250 grain bullet loaded to about 1000 fps and fired in a modern revolver such as the Ruger Blackhawk delivers about as much energy at 50 yards as does the .357 Magnum, and it punches a much bigger hole through things once it gets there.

The .45 ACP and its Colt Government Model pistol hold the distinction of serving longer military careers than any cartridge/firearm combination ever introduced in the United States. Adopted in 1911, both were retired from military duty in 1985 when its foe in many battles, the 9mm Parabellum, became Uncle Sam's "new" cartridge. After serving faithfully for three quarters of a century, the old soldier was put out to pasture as an older and less powerful cartridge took its place.

Even though the .45 ACP is no longer our official military cartridge, it is more popular today among civilian shooters than it ever has been. And its popularity, along with that of the Colt 1911, keeps growing in leaps and bounds despite the introduction of new autoloaders and new cartridges such as the 10mm Auto, .41 Action Express and the .40 S&W. According to "Front Sight", the official publication of the United States Practical Shooting Association (USPSA), over 70 percent of its members still use the .45 ACP in competition. Most of those guns are the old faithful Colt Government model.

[Dakotaphoto]

So if I see a box of ammo labeled .45 Automatic, can I assume that's the sames as .45 ACP?

[MCgunner]

Yes, it .45ACP is .45Auto is .45 Automatic. .45 Colt is a much larger and potentially, in the right gun, much more powerful round in the modern era. All that case volume necessary for the original black powder round comes in pretty useful with a bulky, slow powder like 2400. :evil: The ol' man can still bite and better'n ever.

[Vern Humphrey]

The original .45 Colt blackpowder loads drove a 250 to 255 grain buillet to a velocity of about 1,000 fps -- considerably more powerful than the .45 ACP (a 230 grain bullet at around 830 fps.) However, when the Army was persuaded to buy some Smith and Wesson "Schofield" revolvers, they adopted a new round -- the S&W's cylinder was not long enough for the .45 Colt. The "short" .45s closely duplicated the later .45 ACP. To prevent confusion in ammunition supply, the "short" .45 cartridge (which worked fine in Colt revolvers) became standard.

The Army eventually abandoned the S&Ws, but retained the "short" .45 Cartridge -- as much because soldiers found it more comfortable to shoot as for any other reason, I suspect. The specifications for the new automatic pistol cartridge seem to have been aimed at duplicating the ballistics of the "short" .45.

[Colt46]

Is the correct name for the cartridge. Often it is shortened to .45 ACP, .45 Auto or just .45
Many people incorrectly refer to the actual .45 Colt as the 'Long' Colt. Incorrect, but helpful when purchasing ammo.

S&W has produced a few large frame revolvers chambered for the .45 ACP over the years. Because it is a rimless design they utilize a stamped steel device called 'moon' or 'half moon' clips to insure they function in a cylinder that was designed for rimmed cartridges.

To further muddy the waters, there is another cartridge called the .45 Auto Rim(.45 AR) that was developed for large framed colt and S&W revolvers that were sghipped overseas to take part in WWI. I believe that the .45 AR is an exact duplicate of the .45ACP with the addition of a thick rim to allow for use in conventional revolvers.

Thanks Vern- I realized the water was getting a little deep.

[Vern Humphrey]

I believe that the .45 AR is an exact duplicate of the .45ACP with the addition of a thick rim to allow for use in conventional revolvers.

The .45 Auto Rim is for use in unconventional revolvers -- that is, revolvers chambered for the .45 ACP and meant to be used with half-moon clips. It was developed to allow M1917 revolvers to be shot without the half-moon clips. The rim is very thick -- to allow for the extra headspace required by the half-moon clips.