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45 ACP vs. 9mm: Charles Schwartz Brings Science to the Debate

.45ACP vs. 9mm: Part I
by Charles Schwartz

One of the perpetual debates regarding caliber selection and superiority is “.45ACP vs. the 9mm: Which one is best?”

Enough paper to consume our planet’s remaining forests has likely been expended on the topic and it is probable that there will never be a consensus on the topic. Much of the debate is driven by emotion. Even clearly factual material is hotly debated. Internet forums see the debate of these calibers—among others—as “caliber wars” where the merits of these cartridges, both ‘real’ and ‘imagined’, is debated often until the point of discussions being shut down by forum moderators. Such debate also occurs in local gun shops across the nation, albeit within much more civil environs.

An “apples-to-apples” comparison can be made however, and that is the point of this article and a later, follow-up article to this: to compare the 9mm and the .45ACP on a level playing field. That is to say, this article will provide a comparison of the 9mm and the .45ACP in terms of similar projectile design (both in their full metal jacket round nose configuration) and utility.

A second article will address the comparison of the 9mm and the .45ACP using JHPs, again eliminating as many variables as possible to level the comparison of the two. What better choice than to compare those designs that have been used by our military and through their respective histories gained their respective reputations?

The two cartridges being evaluated in this first article are 1.) the .45ACP 230-grain FMJRN @ 885 ± 25 fps and 2.) the 9mm NATO 124-grain FMJRN @ 1,251 ± 25 fps both of which satisfy Declaration III of the Hague Convention of 1899 which restricts service ammunition to non-expanding designs (that is, full metal jacket) for lawful use by its signatories in military theatres of operation. Both the 9mm and the .45ACP have been around for well over a century now; the 9mm Parabellum (NATO) coming into existence in 1902 and, shortly thereafter, the .45ACP making its debut in 1911. Currently, under STANAG 4090, the 9mm Parabellum is a standard cartridge for NATO forces as well as many non-NATO countries with acceptable projectile weights ranging from 108 to 128 grains, inclusive. STANAG 4090 also specifies acceptable limits of muzzle energy for the 9mm NATO cartridge with a minimum of 400 foot-pounds (542 joules) and a maximum 600 foot-pounds (814 joules) of kinetic energy with cartridges required to have an average operating chamber pressure of 37,000 psi never to exceed 42,700 psi.

The Colt M1911 service pistol in .45ACP

The US military relied upon the Colt M1911 pistol from its adoption in 1911 until it was replaced in 1985 by the Beretta M9 in 9mm Parabellum. The Beretta M9 in 9mm Parabellum was just recently supplanted by the Sig Sauer P320 as the military’s newest service pistol, the M17, also chambered in 9mm Parabellum.

The Sig Sauer M17 service pistol in 9mm Parabellum

Both the Q-model and the mTHOR model, found in Quantitative Ammunition Selection, will be used for this evaluation.

Since non-expanding ammunition configurations such as full metal jacket round nose (FMJRN), semi-wadcutter (SWC), wadcutter (WC) and hard-cast flat nose (HCFN) bullets rarely deform or expand in soft tissue, calibrated ordnance gelatin or in water tests, it is unnecessary to actually fire these projectiles into water for testing since their recovered diameter and recovered weight are usually the same as before being fired. This means that in order to evaluate these projectiles, it is only necessary to apply their initial values (diameter, weight, impact velocity) to the bullet penetration equations found in Quantitative Ammunition Selection to predict their respective terminal performance.

 

.45 ACP (M1911)

Input data for the .45ACP 230-grain FMJRN (M1911):
Diameter: 0.4515 inch
Weight: 230 gr.
Impact Velocity: 885 fps

Predictive Terminal Performance Analysis:
Q-model
DoP: 26.332 inches
Wound Mass: 1.744 ounces
Wound Volume: 2.902 cubic inches

mTHOR
DoP: 27.166 inches
Wound Mass: 1.799 ounces
Wound Volume: 2.994 cubic inches

Cumulative Probability of Incapacitation, P[I/H], for consecutive strikes to a combatant’s torso/abdomen within a 30-second time frame:
1st shot P[I/H]: 66.83 %
2nd shot P[I/H]: 88.99 %
3rd shot P[I/H]: 96.35 %
ΔE15 : -179.954 fpe

9mm NATO (M882)

Input data for the 9mm NATO 124-grain FMJRN (M882):
Diameter: 0.355 inch
Weight: 124 gr.
Impact Velocity: 1,251 fps

Predictive Terminal Performance Analysis:
Q-model
DoP: 29.737 inches
Wound Mass: 1.218 ounces
Wound Volume: 2.026 cubic inches

mTHOR
DoP: 30.395 inches
Wound Mass: 1.245 ounces
Wound Volume: 2.071 cubic inches

Cumulative Probability of Incapacitation, P[I/H], for consecutive strikes to a combatant’s torso/abdomen within a 30-second time frame:
1st shot P[I/H]: 68.86 %
2nd shot P[I/H]: 90.31 %
3rd shot P[I/H]: 96.98 %
ΔE15 : -205.012 fpe

DoP = maximum equivalent depth of penetration in calibrated ordnance gelatin (or soft tissue)
Wound Mass = total weight of tissue damaged/destroyed within the entire wound channel
P[I/H] = probability of incapacitation per hit: Assault, within 30-seconds (US Army BRL P[I/H] model)
ΔE15 = Amount of kinetic energy, in fpe, expended by the bullet from a penetration depth of 1 – 15 centimeters

So, what does all this mean?

It means that we must look to the US Army BRL P[I/H] model for perspective. In 1961, the US Army Ballistic Research Laboratory at Aberdeen Proving Grounds (BRL) produced a mathematically predictive personnel incapacitation model, correlated against Wound Data Munitions Effectiveness Team (WDMET) wound data collected during the Vietnam War, which relies upon the incremental kinetic energy expenditure of a projectile over a penetration depth of 1 to 15 centimeters, or ΔE15, to predict the probability of incapacitation for a random munition strike to the COM (center of mass) of a combatant or an assailant. The US Army BRL P[I/H] model takes the form of,

P[I/H] = [1 + e -(-a + b(logΔE15))]-1,

with the US Army’s BRL P[I/H] model’s coefficients, ‘a’ and ‘b’ being dependent upon the tactical situation with respect to an “assault” of “defense” combatant response mode being modeled. These coefficients can be found in Chapter 10 of Quantitative Ammunition Selection.

Greater values of ΔE15 equate to greater strain energy storage within the surrounding tissues produced by the bullet’s passage through those tissues thereby increasing the likelihood of tissue damage and the probability of incapacitation. Of course, what our bullets hit is also quite important. A ‘hit’ with a .45ACP is always more desirable than a ‘miss’ with a 9mm. Conversely, a ‘hit’ with a 9mm is always more desirable than a ‘miss’ with a .45ACP. That the 9mm is more easily controlled (with its somewhat meager recoil) than the .45ACP only adds to its attractiveness; required second and third (or more!) follow-up shots are always a distinct possibility especially where homicidal aggression is encountered.

From the perspective of lethality, the conclusion that may be drawn from this analysis is that the 9mm NATO 124-grain FMJRN (M882) is the superior choice between the two calibers with a first-round P[I/H] of 68.86%. The .45ACP 230-grain FMJRN (M1911), with a first-round P[I/H] of 66.83%, comes in at a very close second place. For the purpose of this article, the 9mm NATO M882 is the ‘winner’ by a 2.03% margin. In the next article, .45ACP vs. 9mm: Part II, the .45ACP and 9mm cartridges will be examined from the standpoint of how the use of expanding designs effects their respective lethality ratings.

Quantitative Ammunition Selection is available domestically and internationally in hardco  ver, paperback, and eBook formats and may be purchased at www.quantitativeammunitionselection.com