The Obsolete .45 ACP

The .45 ACP cartridge has a strange, cult-like devotion among many American handgunners. Strange because it is practically inferior to more modern pistol cartridges. Its diameter makes it impractical for double-stack magazines (which is not to say those don’t exist: I handled FN’s double-stack FNP-45 but it is far too large for a carry gun), which means capacity is typically just 8 rounds for a full-sized gun. The chamber pressure limit for the cartridge is just 21kpsi, vs. 35-40kpsi for more modern pistol cartridges. This may have been a benefit in the past but with the ubiquity of strong alloys and precise manufacturing technologies it is no longer. It does, however, mean that the cartridge is optimized for propelling heavier bullets at slower velocities, which as I explained in a previous post results in more recoil for a given level of energy. Finally, the heavy bullets and larger dimensions of the cartridge make it significantly more expensive than other defensive pistol cartridges.

The .45 ACP was developed and launched along with the 1911 pistol, so even though 1911s are produced for other calibers there seems to be some nostalgia for shooting 1911s chambered in .45 ACP. But there is also a great deal of lore surrounding the prowess of the cartridge as a “man-stopper.” This is almost certainly rooted in the military’s experience with pistols. The U.S. has followed the 1899 Hague Convention, which prohibits the use of hollow-point bullets in warfare. Until 2010 even military police carried full metal jacket pistol loads. Rifle bullets go fast enough that standard copper jackets break up in soft tissue, creating large wound channels and dumping most of their energy into human targets. But slow, solid handgun bullets punch through human targets practically intact, which means that they leave a wound channel only as wide as the bullet itself. Given this constraint it’s not surprising that .45s developed a reputation for stopping people with fewer shots than smaller bullets that have been government issued.

But this situation does not apply to civilians, who can carry hollow-point bullets. The standard test for terminal ballistic performance is to shoot gelatin that is calibrated to the consistency of animal tissue. The following image shows the wound channel and penetration of standard loads using jacketed hollow-point (JHP) bullets:

Ballistic gel tests of hollow-point pistol rounds

With hollow-point bullets the .45 ACP offers no advantage in stopping power over .40 S&W or .357 SIG (my favorite), which have the advantages of lower recoil, lower cost, and higher magazine capacities.

Energy and Recoil for the pistol rounds shown in the ballistic gel image above
Caliber Bullet
9mm 124gr 1181fps 384ft-lbs 146 1.10x 1x
9mm 147gr 1032fps 348ft-lbs 152 1x 1.04x
.357 SIG 125gr 1319fps 483ft-lbs 165 1.39x 1.13x
.40 S&W 165gr 1076fps 424ft-lbs 178 1.22x 1.21x
.40 S&W 180gr 995fps 396ft-lbs 179 1.14x 1.22x
.45 ACP 230gr 875fps 391ft-lbs 201 1.12x 1.37x

One obvious question is why no .45 cartridge has been specified with higher pressure limits? For example, raising peak pressure to 32kpsi could add 200fps to the load shown here, boosting both Relative Energy and Relative Recoil to 1.7x. One obstacle may be the popularity of 1911 .45s: Neither a standard 1911 nor a standard .45 ACP case can safely support much higher pressures. A few wildcat cartridges have emerged over the years (e.g., .45 Super and .450 SMC) with the same external dimensions and higher pressures, but SAAMI will probably not approve any such cartridges because they could be inadvertently fired in a .45 ACP gun, causing damage and potentially catastrophic failure. SAAMI did approve the .45 Win Mag because its slightly longer cases wouldn’t chamber in a .45 ACP. However that caliber never really caught on, perhaps due to the other problem: power factors above 250 represent a level of recoil that is apparently not practical for a defensive carry pistol.

I recommend this page for further reading on terminal ballistics.

62 thoughts on “The Obsolete .45 ACP

  1. John Lloyd Scharf

    I would only disagree about over-penetration. If it goes through the aggressor and hits any innocent party, over-penetration is more important than under penetration. If I make an inch wide hole from 9 feet with an aggressor, I am not too concerned about how deep it goes.

  2. Charles Darwin

    It’s an excellent round for suppression. The best pistol calibers for suppression are .45 acp and 22lr. The only pistols I have cans for. I tend to carry my 9mm for EDC more often then my compact .45.

  3. federalist Post author

    @Darwin – Good point! Low-pressure, low-velocity rounds are ideal for suppressed shooting, so that’s an argument for the relevance of .45ACP.

  4. Detroit Citizen

    I disagree with John Lloyd Scharf that “there is no such thing as one shot / one kill”, but his assertion brings up the valid point that the .45 acp does INDEED offer the Least chances at a head shot among the major calibers mentioned! Lucas seems to concur above with the contention that shot placement trumps “stopping power”. The .45 acp offers the least chances for effective shot placement among popular calibers within a given size.
    An issue was raised regarding suppressed firearms. This brings to mind the fact that the .40 S&W does indeed offer 180grain rounds at subsonic velocities, while the SAME .40 S&W caliber has highly effective supersonic offerings with bullets of reliably-expanding lighter weights. And again this is with more bullets within a given-size platform. It seems to be a more versatile round when these things are considered.
    In regards to recoil comparisons…I personally prefer a “snappy” recoil that is quickly over-and-done-with, as opposed to a long drawn-out “push” of a recoil that proponents of the .45 acp indicate is common with that caliber. For me it allows me to realign my sights sooner, as my recoil would be complete while the .45 would still be pushing.
    An issue has also been raised in regards to penetration depth. Many favor the FBI standard. My thoughts on this are that, while my preferred .40 S&W load penetrates 10.5 inches at very CLOSE range, due to rapid expansion…this same load will penetrates MORE at a slightly longer distance due to drops in impact-velocity. This increased penetration should satisfy the FBI requirements at the reduced velocity/increased distance. My feeling is that at close range the rapid expansion won’t be a major problem because rounds could more-reliably be directed towards head/neck/upper torso shots. This same rationale should apply also to .357magnum/sig rounds as well as 10mm and other high-speed rapid-expanding rounds. John Lloyd Scharf himself has pointed out using the .22LR example that the Penetration increased when velocity decreased!

  5. John Lloyd Scharf

    I never said, “John Lloyd Scharf himself has pointed out using the .22LR example that the Penetration increased when velocity decreased!”

  6. Detroit Citizen

    To John Lloyd Scharf: Yes sir Indeed you did! I quote below:

    John Lloyd Scharf
    June 13, 2013 at 2:16 am

    In all those ballistic gel pictures, the fact is they can fail to expand. This is particularly so in the case of short barrel revolvers were . In fact, a pistol shot of a .22 Stinger penetrates over 18 inches because it fails to expand, yet is less than 12 inches when forced to expand by hypersonic velocities.

    In this quote you clearly indicate that, in this case regarding the .22 Stinger ammo, the increased “hypersonic” velocities Decreased penetration to 12 inches…as opposed to the Increased penetration of 18 inches exhibited at the decreased velocities attained when the same round was fired from a revolver with a short barrel.

  7. John Lloyd Scharf

    The expansion causes the decreased penetration; NOT the increased velocity. I did not say it was the velocity, which logic and common sense would tell you. I was referring to a HOLLOWPOINT .22LR, NOT ALL .22LR.
    Do not blame me for your improper inference.

  8. Detroit Citizen

    I don’t believe I made an improper inference at all! Immediately above you say/claim, and I QUOTE:

    John Lloyd Scharf
    April 2, 2016 at 12:14 am

    The expansion causes the decreased penetration; NOT the increased velocity.

    You sir even emphasized and Capitalized the “NOT”!

    I will now simply re-refer to what I QUOTED previously above:
    John Lloyd Scharf
    June 13, 2013 at 2:16 am

    … when forced to expand by hypersonic velocities.

    To recap: You first said that the “hypersonic velocities” forced the projectile to expand. And now you say that the increased expansion caused the decreased penetration. Both of these statements are true by-the-way!! BUT then you added that part about “NOT the increased velocity.” Which completely contradicts the truth, and also contradicts what you said previously. And in your conclusion you claimed that I made an “improper inference”, which also is not supported by the facts.

    Thank you.

  9. John Lloyd Scharf

    Increased velocity does not cause decreased penetration, IF the bullet is not a hollow point, AGAIN. Therefore, increased velocity does not decreased penetration. Your logic is flawed.

  10. Detroit Citizen

    Ok let’s stop with the insults such as “your logic is flawed” and “don’t blame me for your improper inference”. These are understandable from a human-nature point of view but they add nothing to the discussion.

    Something I left out from my previous post, for the sake of readability and staying on topic, actually is HIGHLY APPLICABLE now thanks to your statement above.
    Above you claim that, and I QUOTE:
    Increased velocity does not cause decreased penetration, IF the bullet is not a hollow point, 
    However studies have been done regarding SOLID, FMJ, Hague-compliant rounds…again NON-HOLLOWPOINT! It has been shown conclusively in tests of 5.56mm FMJ rounds that penetration at Close-range velocity is LESS than penetration at 300meters, due to the decreased velocity at longer distances causing less deformation and yawing of even the Solid, Non-hollowpoint round.

    That is simply a FACT sir, regardless of whether I have “flawed logic” or not!

Leave a Reply

Your email address will not be published. Required fields are marked *