Pardon the ignorance but it there a difference 45 auto and 45 acp or is it like the 357/38 special- 223/5.56 ? I know one is hotter but are the basically the same? Thanks

The .45 ACP (11.43x23mm Automatic Colt Pistol), also known as the .45 Auto by C.I.P., is a rimless pistol cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the U.S. Army in 1911.  Also known as Pistol, Caliber .45, Automatic, relating to the 1911A1.

As posted before, same round, unless its a +P, which is a different story.

.45 ACP (11.43x23mm Automatic Colt Pistol), also known as the .45 Auto
ETA- beat me to it.

.45ACP was the original name.

Just as what is often mistakenly called .45 Long Colt was .45 Colt.

However companies making single action clones of the Colt revolver stamping their barrels .45 Colt got a lawsuit pressed on them by Colt.

Because of that, they could no longer stamp their barrels .45 Colt, and the ammo companies stop called the ammo .45 Colt, and .45ACP.  Now its called .45 Long, and .45 Auto.

In the end, the lawsuit probably hurt Colt more then it helped them, sort of like the M4 trademark suit.

Of course, then there is the 45 GAP which is a different cartridge from the 45 ACP / 45 Automatic

Whoa, let's set some things right:



1).45 auto and .45acp are the same in +p regardless of the name. +p means the round is up to 10% over the SAAMI standard maximum pressure for the round.  Whether it is .45 +p or .45 ACP +p does not matter.  I am pretty sure the poster understood it this way, but the statement didn't make that clear.

2) .45 Long Colt is not "mistakenly" called that. That is a common name for it, and as a matter of fact, the one Colt uses.  It is stamped on their guns, and it is what they label it.  Check their web site:

http://www.coltsmfg.com/products-c1-q43-Colt_Revolvers.aspx

3) The use of ".45 Long Colt" grew up to avoid confusion in the military, immediately upon introduction in the 1870s, not because of a lawsuit.  A standard military round at the time was the .45 Schofield, which was shorter.  It was commonly called ".45" so to prevent confusion, people started calling the much longer .45  Colt cartridge the ".45 Long Colt."  It made so much sense, Colt adopted the name.

4)  What lawsuit?  This is how S&W labels it's CURRENT production gun - not ".45 Long."  I think you are thinking of that old Sopranos episode, "46 Long."  I personally own a S&W from 1916 stamped on the barrel ".45 Long Colt."  It is not a mistaken name, wrong, nor was their a law suit involved in it's adoption.

The way I understand it is that ".45 Long Colt" has never been an proper term.  Just because everyone uses it doesn't make it right.

There was a .45 Short Colt aka ..45 Colt Government, and the .45 Schofield as you said.

.45 Colt, and .45 Short Colt.  The short round is NOT a Schofield.

You are right that there are several versons of the .45 revolver cartridge, and .45 Colt being the longest of them, quickly started to be called the name "long Colt"  The term Long Colt didn't become popular until after the 1911 had introduced the .45 ACP.

As for the lawsuit.  i don't watch much TV so I don't know what the hell your talking about.
Companies making copies of the SAA were marking the barrel ".45 COLT"  (The PROPER name of the cartridge)  and Colt claimed that customers could be mistaken into buying a clone thinking they were buying a Colt.
Quote "While Colt wholeheartedly supports the ATF and SAAMI marking protocol, there have been others who have exploited these requirements to falsely represent that their firearms are made by Colt. "
Google .45 Colt Lawsuit and you can find more info.

Now on this last point, I am not sure about.  I believe that I have read that the schofield was only purchased as an interim and Calvary weapon, and finally phased out because the Colt was the standard, and the Schofield could not take the standard ammo.

Hell, if we are going to let what ever the majority of people call something to be its proper name, we might as well call all magazines "clips", all cartridges "bullets", and obama "the best president ever".

The quick and dirty:

45 acp = Automatic Colt Pistol

since the game is not just colt any more most people say 45 auto

If I am typing about the cartridge I will note it as .45acp.
If I am talking about it, I will call the caliber .45auto.

And you can see why you could shoot the scofield in the colt .but not the reverse.  Same as the .357Mag and the .357.

Bob

Gentlemen, there was also never technically a .45 Scofield.  The proper name for it is .45 S&W.  But that doesn't seem to stop any of you from using that term.  So argue all you want about the various Colt rounds but you are still using a pervasive term for another chambering.  All of that being said, Colt in order to not use the term S&W got at least one ammo company to call that round the .45 Colt Govt in order to put that on the side of their Colt New Service.  This was also an issue with at least one .38 and .32 chambering.  Was there ever a Long Colt?  No.  Was there a Short Colt?  Yes.  Did people start using a different term to differentiate between the two and all of the other .45 Colt chamberings?  Yes.  Get over it.

The main reason older cartridges have multiple names is not because of lawsuits, but simply because a lot of companies do not want to put a competitor's name on their product.

So a Glock will be labeled .45 Auto, and a Colt will be labeled .45 acp.  (one of my colt's is actually labeled "Colt .45 Auto").  In the old days, it was actually worse. For example .38 S&W and .38 Colt Police Positive are the same cartridge.

45 Auto is shot for 45 Automatic Colt Pistol (ACP).  So it's just a different way to say it/put it on a box.  It is quite different then 38 spl/357 mag.  You can shoot a 38 spl in a 357 , but not vice versus.  The 357 mag round is longer and will not chamber in a 38 special revolver.  Also the 223/5.56 are different rounds as well, although MUCH more similar then a 38 spl and 357 mag..  So, the 45's are a different name, and the other rounds you listed are different rounds.

Thank you. So in short I can shoot 45 ACP out of my 45 AUTO marked springfield with no Problems?

Ive never seen 45 ACP ammo. Only heard of it when people are talking about 1911 pistols. Thanks again

I call it .45 ACP.  I've never had anyone get confused, or not know what I was talking about.  .45 Auto is the exact same thing.  

45 Auto, or 45ACP....

In true AR15.com fashion, get both.

FB

According to ballistics expert Billy Dee Williams, it is properly called Colt .45, and it works every time!

My recently purchased Uberti is marked 45 Colt on the barrel.  Interestingly enough, so is my M1917 Colt, though that one is chambered for the .45 ACP.  As is my Uberti, when I change to the .45 ACP cylinder.

Now, if you want to get really picky, argue over whether it is .38 Super, or Super .38!

So please tell us the different story.

um,,, the .357 mag is not the same as the .38spl. what everyone else is correct... can shoot .38's in a .357 revolver, but not other way... the 357 has a longer case, and much more powerful
just my 2 cents.

Say what? Other than a different primer/powder and maybe a lighter bullet, its the same thing.

And just to add to the confusion, don't buy ammo marked ".45 Auto Rim"  for your 45 ACP or 45 Auto marked pistols.

Uh, It's what COLT calls it.  I think that's reason enough to get over it and accept that ".45 Long Colt" is indeed a common and acceptable way to refer to it.  I am not arguing you should call any round by one name or another.  I am arguing that it is pedantic and silly to deny that a name in common use is in common use.  Just get over and realize there can be two or more ways to refer to a caliber.  What one maker or another uses, and it's just not THAT confusing that anyone should go around correcting someone else.  I know this was a fetish of certain small-minded gun writers in the '70s and '80s, but that's no reason to keep repeating their intolerance and errors in logic.

Call it .45 S&W, Schofield, .45 auto or ACP.  .357 Magnum or .357 Remington Magnum.  It doesn't matter, it's still the same thing.  The names are in common use and probably will stay in common use.  Especially since it's what Colt calls their guns.

If you really want to argue there's no such thing as a "45 Long Colt," I suggest you start by calling Colt and asking THEM to stop using the phrase:

Ding ding ding!  Winner!

Its why Glock doesn't label their 40S&W barrels 40S&W anymore.  Now they just say .40.  
The "45 Auto" nomenclature is a way for companies to avoid putting Automatic Colt Pistol (ACP) on their guns.

45ACP = 45 Auto.
No difference.