Why is there an ACP after .45?

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Automatic Colt Pistol. It's just for that round. It's a .45 caliber round (.45 of an inch around) which was first designed for a pistol manufactured by Colt, thus ACP.
 
ACP=Automatic Colt Pistol,to be able to discern between that and the 45 Colt,now known as 45 Long Colt,which was a common round in the early 20th century.Kinda like the 357 Magnum and the more modern 357 Sig.In both examples,the cartridges are not interchangeable,some method was needed to avoid confusion...
 
. . . which is lucky, because otherwise people might get confused about calibers sometimes. . . .
;)

Caliber nomenclature is crazy stuff.
 
I think it was 1904 or 1905 when the US Government asked commercial manufacturers to come up with a new .45 caliber cartridge. I believe it had something to do with the fact that they were using .38 Long Colt revolvers at the time, which of course was an anemic round with the technology they had at that time. Since low pressure primers, etc. and ball ammo were all there was, the only way to get better performance was a bigger bullet seated in a more powerful cartridge.

The new cartridge was simultaneously developed with the new Colt pistol that would fire it... you might note this footnote in history as the 1911, which of course we all know never went anywhere.;)

Thus the catridge was dubbed the .45 Colt Automatic Pistol, or .45 ACP.

If nothing else it has to be distinguished from say .45 Long Colt somehow.
 
There are lots of different .45 loads. In rough order of development:

1. .45 - sometimes called ".45 Colt", although this is historically inaccurate. This was the load developed for the Colt Model P revolver (known to history as the Single Action Army, or SAA, or colloquially as the "Peacemaker) in 1873.

2. .45 Schofield, or ".45 Short" - developed for the Smith & Wesson Schofield revolver. It was shorter than the original .45, which was too long to fit the Schofield's cylinder. The US Government standardised on this round for a time in the late 19th century, as it was interchangeable between the SAA and Schofield.

3. .45-70 Government - a rifle round, developed during the 1870's for US service rifles. Used by Custer's men at the Little Big Horn, and still popular today for bear defence.

4. .455 - a British round, used in Webley revolvers.

5. .45 ACP - early 1900's, developed without a rim for use in Colt pistols, hence the initials after the number ("Automatic Colt Pistol").

6. .45 GAP - developed in the 1990's for Glock, a shorter, higher-pressure version of the .45 ACP.

There are probably a few others floating around.
 
Prior to the .45 ACP there were revolvers and other guns that used .45 caliber ammunition.
The .45 ACP was specifically designed for the Automatic Colt Pistol (ACP) also known commonly now as the 1911.
The Colt automatic pistol was (and often still is) chambered for .380 ACP and other calibers.
Colt at one time was the major manufacturer of the 1911 type automatic pistol, but many companies have and still do manufacture them.
Three ACP cartridges (.25 ACP, .380 ACP, and .45 ACP) have continued to remain popular, and many guns have been designed to use them.
 
" It's a .45 caliber round (.45 of an inch around)"

.45 of an inch in diameter, not around. If it was designated by 'around' (circumference) then it would be called a 1.42 ACP.
 
Husker1911 wrote

The reason there's "S&W" after .44mag, and "Winchester" after .270. It's named for the cartridge's introducer/developer.
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I know of the .44 S&W Special and the .44 Remington Magnum. Are you getting these mixed up?
 
MedGrl-
Cartridge nomenclature can be extremely confusing, as the numbers are sometimes approximations. Pick a caliber and chances are there are at least a half-dozen cartridges using the same bullet diameter.

Do yourself a favor and pick up a copy of "Cartridges of the World". Runs about $25 at your local sporting goods store and is an invaluable resource, even to the seasoned enthusiast. It gives a fairly detailed description of each cartridge as well as a brief history and ballistic table.
 
Three ACP cartridges (.25 ACP, .380 ACP, and .45 ACP) have continued to remain popular, and many guns have been designed to use them.
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Don't forget .32 ACP, although it's not as popular as the others; maybe that's why you left it out. Personally, I'd like to see more steel-framed small guns chambered in .32 ACP; heck, just bring back the 1908 and I'll be happy.
 
There are probably a few others floating around.
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.45 Auto Rim comes right to mind.

Wow. Thanks for the fast responses. That was just something I had been wondering. Thanks again
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It's actually a fairly Frequently Asked Question. The number (either metric or English) is (roughly -- a ."38 Special" is closer to .36, but ."38" sounds better) the bullet diameter. The verbage after the number is marketing. Anymore, there's nothing much special about ".38 Special". Colt, Glock, Sig, and others have put their names back there. Sometimes it's sort-a descriptive (".45 Auto").

The situation with 9mm cartridges is worse than with .45.

They can call it anything they want, just as long as the Wally World Sporting Goods counter guy can be guided to it in the locked case ("down a row, to your right. Yes, that."):)
 
Funny this comes up today I went to Wal mart to get ammo and when someone finally showed up I asked the guy for a box of 45 ACP he said sorry don't got none we just have 45 Auto so I said that's alrigth I'll just take them then.
 
Sounds like the stupid store clerk I encountered one day who didn't know a half-dozen meant six. :scrutiny:
 
Is that for all .45 calibers or just a certain type of handgun .45 load?
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The .45ACP is only for pistols "chambered" for it, and yes, you can find revolvers chambered for .45ACP. But generaly this cartridge was designed for the "automatic" (semi-auto) pistols such as the 1911 Govt' model, etc. If you look at the older .45 long colt ammo next to the .45ACP you will notice the long colt has a pronounced rim for a revolver style hand gun, while the .45ACP is a "rim-less" design which (correct me here if wrong) chambers or seats on the case mouth and the groove in the rear of the cartridge is for extraction of the round after firing (or just unloading). The rimless design reqiures the use of "Halfmoon" clips to hold them correctly in a revolver.

Hope this helps! :)
 
acp = another crook perforated

another cretin punctured

amazing criminal protection

a-hole control program

afterwards, call police

:scrutiny:
 
For what it' worth, some of the old-old ammo was marked "C.A.P" (Colt Automatic Pistol)...have had some 38/40's marked "CLMR" (Colt Lightening Magazine Rifle...they used a small primer).
 
On the 44 magnum...

Somebody posted the monicker S&W in the title, this it not true, it is called the 44 Rem Mag, because Remington was developing the cartridge for Smith & Wesson, who was developing the revolver for the round. Ruger was also developing a Blackhawk revolver for this round and actually came to market with their 44 mag revolver before Smith & Wesson brought out the famous Model 29.

Other cartrdige names came about not by their developer, but by their loading. Example: the 44-40 and 45-70 were old black powder rounds and the name means a 44 caliber bullet, backed by 40 grains of black powder (44-40) or a 45 caliber bullet, backed by 70 grains of black powder (45-70).

Other rounds are so named, because of their introduction or acceptance as military rounds as well as their diameter. Example: the 30-06 is a 30 caliber rifle round that was accepted into US Army service as the official caliber in 1906...hence the name .30-06.

The naming of cartridges is a very interesting subject!

- Brickboy240
 
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