Difference between 45 acp and 45 colt?

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Prof Young

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So what is the difference between bullets for a 45 acp and 45 colt. Is one bigger, smaller, longer, shorter? Are they relatively interchangeable? I looked at the SAAMI specs but I don't think I understand how to read those.

Talk to me please.

Life is good.
Prof Young
 
.45 Colt tends to use heavier cast bullets with a cannelure (crimp groove). Also it can use flatter nosed bullets because it doesn't have to feed from a magazine.

.45 ACP bullets can be cast or jacketed, but they don't need a cannelure, and they are not quite as heavy as typical Colt bullets.

That said, there is a *lot* of overlap. One of my favorite .45 Colt bullets for plinking is a 240 grain ACP cast bullet. It's the Lee truncated cone mold with the micro- lube grooves. At least I think it's 240; it's been a while since I've used them...

Edit: the Lee bullet is 230 grains, not 240. TL452-230TC
 
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SAAMI does not specify bullets - the actual projectiles - other than diameter and that with a large tolerance.
.45 ACP is shown as .451" jacketed, .452" cast with a +0, - .003" tolerance.
.45 Colt is specified as .456" with a +0, - .006" tolerance.

Most manufacturers hold them closer than that, and a good thing, too. A .448" bullet would be nothing but trouble in used .45 ACP brass.
Nearly all .45 Colt bullets are very close to .452" except a few swaged lead bullets at the old .454" diameter.

Look at the catalog specifications.
A .45 ACP bullet will typically weigh from 185 - 230 grains and will not have a crimp groove, being held only by case neck tension and maybe a bit of taper crimp.

A .45 Colt bullet will typically weigh from 200-260 grains and will have a crimp groove for good bullet pull against recoil forces.

There are plated and coated bullets without crimp groove for .45 Colt and other revolver rounds and they will usually work for casual shooting, but I don't consider them the best.
 
I use 230gr copper FMJ in my Kimber .45 APC and 255gr Keith-style cast in my Taylor/Uberti 1873 Colt .45.

Both are great and accurate and I have no reason to consider if they might be interchangeable.
 
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The SAAMI specs only tell you the SAAMI specs, and in order to fully appreciate both rounds it helps to know the history, which often explains why some things are the way they are.

There are actually books on the subject, some of them are pretty good.

Real quick rough history (and leaving out some interesting details for brevity)

1873 Colt introduces the Single Action Army (aka model P aka Peacemaker) and the .45 Colt cartridge. First batch of guns goes to the Army....

The .45 Colt was loaded with a .454" 255gr "conical flat point" bullet. This is a somewhat pointed round nose with a small flat tip.

It was loaded over 40gr black powder and would deliver 900fps+ depending on the barrel length.

In 1875 the Army buys some of the S&W Schofield revolvers. While the break action of the S&W offered much faster reloading than the Colt, the S&W cylinder wasn't long enough to take the .45 Colt cartridge.

The .45 Schofield is a shorter case than the .45 Colt, and was loaded witb a 230gr bullet over 28gr of black powder and delivered 830-850fps

Both guns served until the 1890s when the Army went to the .38 Colt. Both types of ammo, .45 long and short were in inventory. The S&Ws could only shoot the short round, the Colt could shoot both. This is probably the time when the .45 Colt came to be called "Long Colt"

The .38's performance in combat (Moro uprising) was ...less than desired, and officers in the Philippines urgently asked for .45s Some Colts were "dusted off" and sent.

By 1905 the Army is pretty well decided its next pistol will be a semi auto, and they want a .45 caliber. In 1910 Browning delivered a prototype pistol and a .45 caliber round that met the Army requirement (230gr @ 830ish fps) and when adopted in 1911 Colt built the guns. The Army got .45 Schofield ballistics, which they knew worked, in a semi auto pistol.

SO, you've got an older revolver round, originally black powder, and a newer shorter case rimless semiauto pistol round with slight dimensional differences in bullet diameter, and significant differences in bullet design. However there is overlap, and other designs appear that work in both rounds.

After WWII (when colt wasn't making SAAs) other makers made .45 Colt guns with barrels of .451 /.452" instead of the original .454"
This was to work better with .45acp bullets and the .454" .45 Colt slugs squeezed down just fine.

SO, today we have SA revolvers shooting either Colt or ACP bullets, and some that can fire either ammo, such as the Ruger .45 Convertible.

I've skipped a LOT. Happy to answer specific questions, what is it you need to know?
 
Keep in mind, contrary to popular belief, the .45ACP
is based on the .45 S&W and NOT the .45 Colt.
 
The .45ACP case was designed by Browning, to work in the pistol he was designing. The ballistics of the ammo were specified by the Army, which duplicated the .45 S&W bullet weight and speed.
 
I agree with everyone. The bullets are pretty much interchangeable. I typically use lighter weight .45 colt bullets in my .45 auto rim cases simply because the cannelure allows for a crimp.

"45 AMP's" history is fascinating, and as he said, not everything can be covered, because entire books have been written on the topic. However, an interesting side note is that there was a third army issued cartridge: the .45 colt government. THe .45 scholfield has a slightly larger rim than the 45 colt, and due to manufacturing tolerances for guns an ammunition at the time, the .45 schofield would sometimes not chamber in the single action colt revolver because of rim interference. Therefore the army issued the .45 colt government, which had the length of the scholfield cartridge, but the rim diameter of the .45 colt cartridge. Unfortunately that solved one problem, but created another. The smaller rim of the .45 government wouldn't always provide positive extraction in the scholfield revolvers.

However, maybe the ones who have been calling the 45 colt, the .45 long colt have been right. I think you could legitimately describe the .45 colt government as a .45 "short" colt, and therefore there really was a .45 short colt.
 
In practical reloading terms these are two very different cartridges: One for revolvers, crimped, and heavier bullets. The other for auto loading pistols, headspacing on the case mouth, and a shorter length for magazine feeding. 45 ACP loads are lower velocity. Due to the lower velocity, using even heavier bullets in 45 ACP seems pointless. I choose lighter bullets for 45 ACP for higher velocity: 185 to 200 grains for 1000-1100 fps.
Also, my Glock 45 ACP has a capacity of 13+1, with 2 spare mags that is 40 rounds on a belt.. Can't do that with a 6-gun.
 
I only recently saw the specs on the 1906 Frankford Arsenal .45 ammo. It is not the same as either the final .45 ACP or the original 1905 Colt .45 Rimless Smokeless. Apparently the 1911 .45 ACP is the Colt case and the FA bullet, or pretty close.

Major Schofield may have had a little help getting his design made by S&W and adopted by the Army. His brother General Schofield was then chief of Army Ordnance.
He later grew despondent and shot himself.
Apparently his nephew, also a Major, did, too.
 
So what is the difference between bullets for a 45 acp and 45 colt. Is one bigger, smaller, longer, shorter? Are they relatively interchangeable?
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Prof Young,

As previously stated, .45 Colt bullets tend to run a little bit heavier. Also, due to them being fired in a revolver, .45 Colt bullets will have either a cannelure or crimp groove to allow for a roll crimp, while this is typically not found on .45 ACP bullets due to them being taper crimped. Get the right bullet and it can be used in either cartridge, such as the Lyman 452423 bullet on the left that was designed for a revolver (.45 AR), but works equally well in a semi-auto.

Don

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Think of a 280gr SWC at 1050 in Colt versus a 200gr SWC at 1000 in the Auto. That 280 blows through hogs and deer to 40 yards at any angle.
 
About 1909 the .45 Colt case was redesigned, with a slightly larger rim than the original, to provide more positive function with the DA revolvers then coming into use.

Up until the last couple decades or so, the heaviest .45 Colt slugs were about 260gr.

Any of the ACP bullets can be used in the .45 Colt. Even ones without cannelures. It's a matter of loading technique, and not trying to go beyond the bullets limitations.

Some ACP bullet are/were made to go both ways.

here's a bit of a side note, you may see the term "Ruger Only" with some .45 Colt loads. It's a little confusing today, because there are now Rugers that won't take the "ruger only" load levels.

In the early 70s various handloaders began experimenting with heavy loads in the Ruger Blackhawk .45 Colt. THAT Ruger is built on the same frame size as their .44 Magnum Super Blackhawk. And it was found that the Ruger would handle loads in the .44 Magnum class. These loads became known as "Ruger only" loads, and there was only one Ruger in .45 Colt at the time.

Later, Ruger introduced the "Vaquero", which was also built on the big 44 mag size frame. They will also handle "Ruger only" loads.

A decade or so later, Ruger dropped the Vaquero, and replaced it with the "New Vaquero". (Important! Even though the names are almost the same the GUNS ARE NOT!)

The 'NEW VAQUERO" is a smaller frame gun than the Blackhawk or Vaquero, it is the same size (roughly) as the Colt SAA, and should be used with the same pressure as the Colt SAA and NOT "Ruger only" level loads.

There are a lot of tips and tricks used nowdays, loading the .45 Colt for different guns, at levels ranging from the light loads used in Cowboy Action Shooting up to .44 Mag levels (and possibly a bit beyond) is those guns capable of handling that level pressure.

Every gun marked .45 Colt is NOT able to handle every .45 Colt load combination. If you're wanting something above the original black powder speed and pressure, you need to do some research into the gun you have, and its capabilities and limits.

I've been shooting .45 Colt since the early 80s, in Ruger NM Blackhawks and later Vaqueros. Had my days of making a magnum out of the .45 Colt, and settled on one load a 250gr SWC at just a hair under 1100fps from my 7.5" gund. Works well, has a lot of "thwop!" and while it has noticeable recoil, its not so bad as to be unpleasant, for me, anyway. When/if I want more than that, I go to a .44 Mag. by choice.

Happy to answer any specific questions I can.
Both the .45s are great rounds, and are found in some of the best guns ever made. (also found in some cheap crap, too, so be sure the gun you get is the one you WANT. :D)
 
A lot of very useful info has been given above, but a quick and dirty answer to you question is:

Any handgun bullet of .45 caliber will function in a .45 Colt.

Only specific profile .45 caliber bullets will function (feed) in a .45 ACP.

Thus, you can use any .45 ACP bullet in the .45 Colt but not vice versa.

Note that the powder loads, OAL, and most every thing else is different. Check your loading books for specifics.
 
Only specific profile .45 caliber bullets will function (feed) in a .45 ACP {semi-auto handgun}.
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Some of us use revolvers with the .45 ACP cartridge where the bullet profile isn't as 'much' of an issue. Always exceptions :) .
 
Some of us use revolvers with the .45 ACP cartridge where the bullet profile isn't as 'much' of an issue. Always exceptions .
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Okay, I'll add one word to my post:

Any handgun bullet of .45 caliber will function in a .45 Colt REVOLVER.

And just to be safe: Or in single shot .45 caliber rifles.:D
 
Only specific profile .45 caliber bullets will function (feed) in a .45 ACP.

Thus, you can use any .45 ACP bullet in the .45 Colt but not vice versa.
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Nope. See the bullet on the left in the pic in post #12. It's a .45 caliber revolver bullet that functions fine in a .45 ACP pistol.

Don
 
Thus, you can use any .45 ACP bullet in the .45 Colt but not vice versa.
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Not quite true. Every .45 bullet can work in both cartridges, but every .45 caliber bullet won't work in every GUN.

I've got .45 caliber revolvers and single shots in both .45 Colt nd .45ACP. Every .45 caliber pistol bullet can be used in those guns.

I've also got semi auto pistols in .45 ACP. Only certain bullet weights. profiles and lengths will work in those guns (and function as repeaters).
 
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