This is the first of a three part series on caliber selection. The
primary focus in the series will be handgun cartridges for self-defense;
however, the math and science discussed here also applies to target shooting
and hunting as well as rifle cartridges.
Warning, I will attempt to get technical with data in this series posts.
I will also attempt to make that less painful than it sounds. No guarantees.
Disclaimer: I am an unabashed fan of the .45ACP cartridge and the guns
that shoot them especially the 1911. I also own or have owned and loved guns
chambered in .22LR, 9mm, .40 S&W, .357 Magnum and .44 Magnum. It is not the
intent of this article to advocate for any particular cartridge as the “best
cartridge” for everyone and every situation. The intent is to provide
information to help you decide what’s best for you and your situation. I will
offer up a personal opinion at the end for what that’s worth.
For those who are not interested in reading to the end, please allow me
to sum things up for you right here. All calibers (rifle, shotgun or handgun)
are a set of compromises, and different calibers do some things better than
others. One size does not fit all. I don’t want to get shot with any of them.
No one caliber can do it all (though some get closer than others). Only hits on
target count, you can’t miss fast enough to win, and a slow hit beats a fast
miss. If you can’t get hits with a particular gun/caliber, it is useless to
you. You have to decide what works best for you not what works best for some
data crunching gun nerd on the internet. Go to the gun range, beg, borrow or
rent one of each caliber/gun combination you are considering (to the extent
possible) and try before you buy. You’re welcome.
Now that the disclaimers, caveats, summaries and provisos are out of
the way, let’s get busy.
If I had it my way, I’d have a huge collection of guns in every caliber
possible with enough ammo to shoot them whenever I wanted. But, since I don’t
live in the alternate reality where I won the lottery, I must make “wise”
choices about what I do choose to buy. Statistically speaking, they're more
people out there in the same boat as me than not. So, chances are good you need
just as much help as I do making the best choice of caliber for your own
individual circumstances (hint: it’s not the same for everyone).
To that end, the table below has some data points I will be referring
to in the rest of the article for three common semi-automatic pistol calibers
in use today. If you are interested in crunching your own numbers on different
loads or calibers, part three in the series will jump into the deeper waters
with the science and equations so you can go math yourself silly. However, some
information, like SAAMI Max Pressure and charge weights, must be looked up or
measured as opposed to calculated.
Caliber
|
9x19 mm
|
.40 S&W
|
.45 ACP
|
Bullet Diameter
|
9mm / .355 in.
|
10mm / .40 in.
|
11.5mm / .451 in.
|
Overall Cartridge Length
|
1.168 in.
|
1.135 in.
|
1.275 in.
|
Load
|
124 gr. @ 1115 fps
|
165 gr. @ 1130 fps
|
230 gr. @ 900 fps
|
Muzzle Energy
|
342 ft. lbs.
|
468 ft. lbs.
|
413 ft. lbs.
|
Bullet Area
|
0.10 sq. in.
|
0.126 sq. in.
|
.16 sq. in.
|
Bullet Momentum
|
19.75 ft.lbs/sec
|
26.64 ft.lbs/sec
|
29.57 ft.lbs/sec
|
Sectional Density
|
.140
|
.147
|
.161
|
Recoil Energy/Velocity
|
6.0 ft.lbs./16.0 fps
|
9.3 ft.lbs./19.9 fps
|
7.5 ft.lbs./13.9 fps
|
SAAMI Max Pressure
|
35,000 psi
|
35,000 psi
|
21,000 psi
|
So, let’s get the obvious out of the way. Larger caliber bullets are
bigger and heavier than smaller caliber bullets. There’s a shocker for you.
Thank you, Captain Obvious.
Yes, but, look at the other dimensions for a moment. There is only a
2.5mm / 0.096 in. difference in diameter between the 9mm and the .45 ACP, and there
is only a 0.107 in. difference in the overall cartridge lengths between the two.
However, those little fractions of an inch make huge differences in the design
of the guns that fire these cartridges. From little things like the size of the
bolt face to the size and position of the extractors and ejectors, to feed ramp
angles, to bigger things like frame size, grips and magazines. Those fractions
of an inch add up. For instance, most polymer .40 S&W guns can easily
convert to shoot 9mm with a simple barrel swap. You cannot do the opposite
conversion because the breech face on 9mm guns is not large enough to
accommodate the case rim of the .40 S&W even though they are only 1mm
different in size.
So, if versatility and modularity are important to you, a gun chambered
in .357Sig (which is essentially a necked down .40S&W case) or .40S&W
may be a better choice than a gun chambered 9mm or .45ACP.
Another size related consideration is frame/grip size. Due to the
longer overall case length of the .45ACP, guns chambered in .45 generally have
a larger frame/grip than 9mm/.40S&W chambered guns. Technology advances in
polymer handgun design has mitigated this problem somewhat, but those little
0.096 inch / 0.107 inch dimensional differences require bigger magazines which
require bigger magazine wells which adds up to bigger frames and longer trigger
reach. Those shooters with small hands/short fingers may find it difficult to
hold and control the larger framed guns. It’s one of the reasons the FBI went
from the 10mm to the .40 S&W and now back to the 9mm. I have pretty good
sized hands with longish fingers, and even I have trouble with some designs
(the Sig P220/P227 in has a fat grip/long trigger reach combination that
doesn’t work well for me). Bottom line, more people will have an easier time
finding a comfortable fit with a 9mm than a larger caliber such as a .45ACP or
10mm.
Moving on, let’s compare the size of the bullets themselves because
size matters or so I’ve been told. If you hang around the gun community long
enough, you’ll hear somebody say things like “carry something beginning with a
4”, “a 9mm may expand to a .45, but a .45 will never shrink to a 9mm”, or “I
carry a .45 because they don’t make a .46”. My best friend gave me a t-shirt
that says “.45 because shooting twice is silly”. While most of these sayings
are just hyperbole and ignorant macho nonsense, differences in bullet size may
be important to some especially those living in restrictive states or cities
that have limits on magazine capacity.
The diameter of a .45 is only about 27% larger than the 9mm, the cross-sectional
surface area (think of the flat top of a wad cutter) is 60% larger. In other
words, it takes 3 9mm bullets to make entry holes covering roughly the same number
of square inches as 2 .45s. Bullets do weird things once they go through things
like car doors, clothing, skin, bone, etc. So, there is no precise way to
compare wound channels or hollow point expansion except in general terms.
Generally speaking, a larger bullet will make a larger wound channel and expand
to a larger diameter than a smaller bullet. So, bigger hole is better. Right?
Maybe. It depends on your intended usage and circumstances. There are
situations where quantity can be a quality all its own.
So, let’s take a few moments to discuss size versus quantity in the
self defense context. Size and capacity really don’t matter in target shooting
unless you are involved in organized shooting sports with rules specifying
calibers and capacities. For hunting, size and capacity may have a minimum
requirement or be limited by law.
The object of any self-defense weapon is to stop a threat (whether the
threat is human, animal, vegetable, vehicular or killer robot). A bullet can do
this in one of three ways: 1) turning the lights out by hitting the threat’s
central nervous system, or 2) poking holes in the body allowing air to get in
and blood or other vital fluids to get out, or 3) wrecking the skeletal
structure to the point that further movement is limited or impossible.
A shot to the CNS is the best way to stop a threat. Unfortunately, it’s
also one of the hardest shots to make under stressful conditions…like a home
invasion, assault or other social unpleasantness. The spinal cord is between ¼
and a ½ inch thick depending on where in the spine you poke it. The medulla
oblongata is a little over an inch long, and the other critical areas of the
brain are not much bigger than that. If you think you can hit those targets on
command when your heart rate is through the roof due to an adrenaline dump, mad
respect to you and buy me a lottery ticket while you’re at it. This is the
reason people are trained to shoot center of mass because hitting a moving
target barely bigger than your bullet borders on the impossible.
For the sake of argument, let’s say you’re a good shot, calm under
stress and you want the best chance of hitting the CNS. A .45 with 10 rounds
(like, say, a Glock 30s), you have 11 chances (10 rounds in the magazine plus
one in the chamber) to turn the lights out. Those 11 chances are slightly more
forgiving of less than perfect aim than the smaller 9mm, but not by much. If we
change the gun to a similarly sized 9mm (like, say, a Glock 19), you have 16
chances (15 rounds in the magazine plus one in the chamber). 16 chances are
more than 11 chances pretty much everyday of the week. However, if you live in
a restrictive state that limits magazine capacity to 10 rounds, maybe the
bigger bullet makes more sense for you.
Now, let’s move on to bloodletting. It’s pretty much a no brainer that
bigger holes let more blood out faster and more force breaks bones easier. Again,
if you are in a restrictive state, bigger bullets may make more sense for you
than smaller bullets. Outside of restrictive states, some people like to tout
the capacity advantage of the 9mm over the .45ACP. As discussed above, it takes
3 9mms to open roughly the same surface area as 2 .45s. So, unless you are
successful in a 1 shot stop, the capacity “advantage” of the 9mm is pretty well
washed away when you consider the fact that it takes 15 rounds of 9mm to create
the same area of holes as 10 rounds of .45.
Bone breaking is hard work. A quick check with Google says it takes
almost 900 ft.lbs. of energy to make a clean break a femur which is one of the
hardest bones in the body. However, we don’t need to cleanly break the bone;
and, besides, that’s not how bullets work. Bullets crush and shatter outward
from the point of impact. All handgun cartridges above 9mm are capable of
breaking bones. Even the lowly .22LR can poke through some of the thinner
bones.
The femur itself is not
very wide (roughly an inch or so…wider at the ends) which will be a tough shot
on a moving target at up to 7 yards while amped up on adrenaline. But, the
femur and pelvic girdle are also home to the femoral artery and a lot of other
necessary circulatory stuff. So, back to our discussion a moment ago about the
CNS, do you want a bigger round slightly more forgiving of less than perfect
aim, or do you want more chances to hit the target?
Another consideration is the weight of the ammunition because ounces
equals pounds and pounds equals pain. If you are going to carry a gun for self
defense, you have to schlep whatever you choose. A 124 grain 9mm bullet is 0.283
ounces, and a 230 grain .45 ACP bullet is almost double the weight at 0.525 ounces.
And that’s before you even factor in the weight of the cartridge case and
powder. A little more Google Fu says a 124 grain 9mm case, powder and
projectile run about 0.444 of an ounce vs. the .45 at 0.737 ounces.
What does that mean for a typical concealed carry load out of one
magazine in the gun and one reload? A 9mm Glock 19 carries 15+1 rounds in the
gun. So, gun + reload comes to a total weight of 36.97 ounces. For a polymer to
polymer comparison, a Glock 30s (which has 10 round magazines and is close in
dimensions to the G19) with an extra reload tips the scales at 37.77 ounces.
Less than an ounce difference.
For another interesting apples to apples comparison, let’s compare the
Smith & Wesson M&P Shield9 vs. the M&P Shield45. The Shield9 holds 7+1 or 8+1
depending on the magazine, and Smith & Wesson lists the weight as 18.1
ounces (they do not however say whether that is a laden or unladen swallow).
The Shield45 claims a 6+1 or 7+1 capacity and a weight of 20.5 ounces. For the
sake of argument, we will assume S&W is reporting unloaded weights which
makes a full gun and reload 25.65 and 31.56 ounces for the Shield9 and Shield45
respectively. That’s just shy of 6 ounces.
Muzzle energy is pretty much a wash between the 9mm, .40S&W and the
.45ACP when you get right down to it. The .40S&W has a slight edge over the
9mm and .45ACP in the energy category and is also available in a wider range of
bullet weights; however, it comes at the cost of increased felt recoil. More
energy is generally preferable to less energy in any given situation; however,
too much energy can be a bad thing too. No one I know seriously recommends a .500
S&W magnum for home defense because of the possibility of over penetration.
Since muzzle energy is a function of bullet weight and velocity, we get back to
trade offs again. Lighter bullets typically move faster than bigger bullets,
but shorter barrels allow for less time for powder expansion resulting in lower
velocities. So, a bullet fired from a 3 inch barreled gun is going to have less
velocity and correspondingly less energy than the same bullet fired from a 4
inch gun. Go look at the charts on Ballistics by the Inch if you are really interested in digging into this in detail.
That leads us to momentum. Back to physics class. Isaac Newton was a
smart cookie. The Laws of Motion state that objects in motion tend to stay in
motion unless acted upon by an outside force and objects at rest tend to stay
at rest unless acted upon by an outside force. Momentum coupled with sectional
density is a pretty good indicator of how well a particular bullet will
penetrate. Having said that, most modern self defense ammunition regardless of
caliber is designed to meet the FBI recommendations for ballistic gelatin
penetration of 12 to 18 inches. There’s some really good information on this
done by others out there. Lucky Gunner’s test is pretty thorough and worth a
look.
Back to Newtonian physics, the “at rest” part of the laws of motion is
your recoil. That big, fat, happy .45ACP needs a little heftier shove to get
going in the morning than the smaller, lighter, zippy 9mm. We also have to pay
the piper for one of Newton’s other notions: for every action there is an equal
and opposite reaction. If you have 342 ft.lbs. of energy exiting the barrel
stage right, you also have to deal with 342 ft. lbs. of energy pushing the gun,
your hand and everything else stage left. This is where the weight of the gun,
the stiffness of the recoil spring, etc. come into play to mitigate recoil, and
it’s why no one enjoys shooting scandium or polymer framed, snub nosed .357
magnums. In part three, I’ll give you a link to a recoil calculator you can
play with. I think it’s neat, but I’m an admitted data nerd.
Looking back at the chart, .45ACP has the best momentum number, and its
recoil numbers are actually better than the .40S&W. If you are recoil
sensitive, 9mm is a good choice for you.
Handguns exist as light weight, concealable, personal defense weapons
(at least in comparison to rifles and shotguns) to get you out situations you’d
rather not be in. I said at the beginning that it was not my intent to advocate
for one caliber over another as the best for everyone and every situation. I
will, however, offer up the following as my personal opinion:
For the majority of shooters including those new to the sport as well
as those people who rarely, if ever, shoot and have a gun “just in case”, the
9mm offers the best compromise of capacity, size, shootability, economy, etc.
and is more than adequate for most situations. Bigger, more powerful calibers
are more appropriate to “expert” shooters and those knowingly making a
trade-off for a specific reason (e.g. living in a restrictive state or in bear
country, those that want to shoot major power factor in competition, etc.). Pick
the one you shoot the best. Practice as much as you can afford (we’ll talk
about the economics in part two), and quit worrying about