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.45 auto & .45 ACP

TheRoyalDoyle
I am new to guns, and am wondering what the difference is between a .45auto round and .45 ACP.
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8 comments

Date Votes
  • Laredo Lefty
    Nothing. They are the same round. Just 2 different ways of refering to the same cartridge. The ACP stands for "Automatic Colt Pistol".
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  • perry shooter
    Hello for the most part if you live in the U.S.A they are one in the same .45ACP (AUTOMATIC COLT PISTOL) there is also 38ACP 32ACP and 25ACP There are some other 45 Caliber cartridges 45 Gap and 45 Webley that are shot in Semi Auto pistols. Hope this helps Karl.
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  • JohnnyBGood
    In 99.99% of the cases they are one and the same. However, be aware that there is the .45 Auto Rim (AR) which is the .45 ACP with a rim that allowed it to be used in revolvers.

    John
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  • KySilverado
    The cartridge name, according to my latest Hornady handbook, is 45 Automatic. Quote from it "45 ACP is a moniker commonly used to describe the 45 Automatic, however this is the incorrect description of the cartridge, but is the correct descriptor for the gun the cartridge is fired in."

    I've always called it 45ACP.
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  • beantownshootah
    As mentioned, there are other obscure .45 caliber cartridges that can be fired in autos.

    But in GENERAL anyone refering to a ".45 auto" cartridge with no other explanation is talking about a .45 ACP (automatic Colt pistol). In practice the terms are synonymous.

    I have to disagree with Hornady stating that its incorrect to refer to the cartridge as ".45 ACP". In my opinion, not only is Hornady wrong, but ".45 ACP" is the PREFERRED way to refer to the round in question.

    For one thing, the cartridge has been widely known as "45 ACP" and if for no other reason other than wide recognition and popular usage, its correct. As mentioned above, its also unambiguous, since there are technically other kinds of .45 auto cartridges.

    I'd also argue that its historically correct as well, as Colt was the first major manufacturer of guns chambered in that round, and was the ONLY manufacturer of guns chambered in that round for decades (or at least the biggest one). Its not necessarily true anymore but for DECADES the terms ".45 auto" and "Colt pistol" were synonymous.

    Lastly, there are plenty of recent manufacture NON-Colt guns that are labelled ".45 ACP". For example, Taurus labels its guns .45 ACP. Taurus, obviously, isn't Colt, so contrary to what Hornady claims, how could the term "ACP" on the frame of a Taurus be referring to a Colt pistol? Is Taurus wrong? How about Smith and Wesson, which also used the term .45 ACP?

    As a separate issue, note that there is at least one major gunmaker that appears to refuse to use the name of competing gunmakers in labelling its guns!

    So intead of the .45 Automatic COLT pistol, it labels its guns as ".45 auto" and instead of .40 SMITH AND WESSON, it labels its gun as ".40 auto".

    Not surprisingly, this same company has no problem labelling its own proprietary (and IMO mostly pointless) cartridge as ".45 GAP".
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  • MFI
    Make sure you dont mix it up with .45 Colt either..
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  • ColtDoctor
    Beantown is right. Even Colt would call 32 S&W - 32 Colt New Police, etc... Nobody likes advertising for the competition! It gives us gun cranks many hours of study for such idiosyncrasies.
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  • Riomouse911
    And just for fun, as was mentioned earlier Glock came up with the somewhat short lived .45 GAP... which is a shortened .45 Auto case loaded to higher pressure for .45 ACP performance using a 9mm sized grip frame. It stands for "Glock Aotumatic Pistol. They will not shoot reliably in a .45 ACP because the chamber in the ACP is longer then the GAP case. You may sometimes run into a box of the the .45 GAP round in larger stores, but they're pretty much gone now.

    I own a .45 Super, which is a stronger .45 ACP sized case loaded with .45 ACP bullets for higher velocity/energy. This was along the lines of the 1970's-1980's era .451 Detonics cartridge, which is very, very rare. If you find a rare box of .45 Super, or an even rarer box of .451, DONT USE THESE in a .45 ACP, they might ruin the gun... or worse. The now pretty much obsolete .45 Winchetser magnum is another .45 ACP based cartridge using a longer case and higher pressures for .44 magnum power. LAR Grizzly's were chambered for this (1911 style) along with the gas operated Wildty Auto-mag.

    Learing about guns and calibers is fun, and holds a lot of history. For info beyond your wildest dreams get a copy of Cartridges of the World by Frank Barnes. I got my office a copy of the 11th edition last month for 17 bucks on Amazon.
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