Which Ammo Is Better – 9mm vs 45 ACP? We Compare To Two Sluggers

Which ammo is better – 9mm or 45 ACP?

Unless you are entirely new to the world of handguns, this is an argument that you have heard played out ad nauseam more times than you would care to remember. I’m going to start by laying it out plainly right from the beginning.

With regard to modern handgun ammunition, these are both reliable calibers for stopping a threat. Frankly, these are the two premier calibers for self defense and home defense in my opinion. That doesn’t mean that they are without pros and cons, nor does it mean that either is appropriate for every circumstance without exception.

The Elephant in the Room – Stopping Power

This is the point of contention that this debate most frequently hinges upon, and it is a valid concern. Modern ballistic testing has shown that quality ammunition in the most common loads of both 9mm and 45 ACP has a statistical difference in the ability to stop a threat. Your average 45 ACP round is estimated to take between 1-1.2 rounds while 9mm averages 1.8-2. Naturally, this varies as you move up and down the scale of load weight and even into the +P or +P+ arena. 45 ACP purists will say that the debate ends right there, but it doesn’t.

A statistical difference is just math. Broken down to basics, those numbers mean that 45 ACP generally “stops” a threat in one hit but occasionally takes two or more while 9mm “stops” a threat in two or more but sometimes takes one. You can’t throw 0.2 of a bullet down range, so these numbers are an aggregation of the frequency of one or multiple hit encounters. If you’re carrying a 7+1 capacity 1911, one round is 12.5% of your carrying capacity. Now if you have a 17+1 capacity 9mm pistol, one round is 5.6%, and even two rounds would be only 11.1% of your ammunition. Add additional magazines and those numbers only swing further in the 9mm’s favor.

Math alone shouldn’t be the sole reason for you to select one caliber over another because shooting encounters don’t happen in a vacuum. There are numerous other considerations that affect so called “stopping power” which bring us to our next point.

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When It Matters – Accuracy and Reliability

I’ll dispense with the reliability portion in one simple phrase – garbage in, garbage out. If you plan on placing your life in the hands of a cheap, bargain basement firearm or ammunition, then the responsibility for its eventual failure lies squarely at your own feet. We’ll get into specific cost differences later, but this is the part when I climb on my soapbox and berate you about maintaining your firearm and buying good quality ammunition and guns. There is no justifiable reason to settle for questionable products when it comes to something as critical as guns and ammo. In the same vein, regularly shoot, clean, and function test your weapons. The only ones who will end up regretting you skipping that step will be you and those you care about.

With accuracy, I won’t break out specific statistics again as they are easily located with a quick internet search, but the concept in general is very simple. The exit velocity and subsequent speed of a bullet is a factor of the weight of the round and the quantity of the propellant in the load. As speed decreases over distance and gravity acts upon the round, bullet drop increases the further that you get from the muzzle of the weapon. With equal grain loads, a heavier round will produce a lower exit velocity, and the rate of drop will be exponentially faster as well. Due to the higher speeds and lower projectile weight, this means that the 9mm is inherently more accurate from a purely scientific standpoint.

All this is without accounting for barrel twist. A projectile with a higher rotational velocity will stay on target longer. 9mm pistols can produce rotational speeds that are as high as double that of your average 45 ACP. As we discussed, shootings don’t happen in a lab. The primary factor that affects accuracy overall is your level of training and consistent practice. In addition, I don’t generally recommend getting into a gunfight at a significant distance with a pistol if you can at all avoid it.

A second consideration is accuracy in follow up shots as anything worth shooting is probably worth shooting twice. Felt recoil and muzzle lift are both functions of load weight, projectile weight, and slide weight when speaking about modern semiautomatic pistols. Heavier projectiles cause less muzzle lift and felt recoil, and heavier slides produce the same results. This is something to keep in mind when selecting your pistol as compact and subcompact pistols are inherently going to have more felt recoil. Again, the major factor in follow-up shot accuracy is going to be the shooter’s proficiency or lack thereof. Neither of these calibers is a pig to shoot in a subcompact or micro compact weapon, but you should try before you buy as I always suggest.

Penetration – Which Caliber Gets Through The Target

Penetration concerns are twofold. First, you want to make sure that your bullet of choice penetrates your target deeply enough to hit the important bits. According to the FBI, that ideal depth is 12-18 inches. The good news is that both calibers come in loads from reliable manufacturers that consistently produce penetration depths of that distance in ballistic gel. The edge here actually goes to 45 ACP as higher grain weight +P and +P+ 9mm rounds have a tendency to over penetrate even with jacketed hollow points.

The second area of penetration that is important is environmental penetration. Sometimes you want to shoot through things and sometimes you really don’t. Think of law enforcement or anyone who needs to put rounds through a car door or another surface. Logically, you might think that the larger round would perform better, but it’s actually the higher internal pressure and greater speeds of the 9mm because of its lighter weight that allows it to punch through things more efficiently. The larger round slows down faster.

This is a plus in home defense scenarios for the 45 ACP. If you miss the bad guy, the 45 caliber round is much less likely to barrel through room after room of drywall and endanger unsuspecting family members. Some could argue that hollow point ammunition solves this problem, but there have been documented incidents where sheetrock actually plugged the nose of a JHP round effectively turning it into ball ammo.

Getting Practical – Cost and Availability

This is where things can get really ugly. The 9mm round is preferred by many militaries and law enforcement agencies around the world, and because of that, production is at such a high rate that this caliber is generally more readily available than most other pistol calibers. A review of popular ammunition wholesaler websites showed that of the over 300 possible variations of 9mm ammo available only 50 were currently in stock with prices ranging between $1 to $1.50 per round based on bulk ordering and specifics.

When it comes to 45 ACP, there are not as many options to choose from, and of the 230 products commonly available, only seven were actually in stock. Prices for decent ammo started at $1.50 per round and went up to over $2 rather quickly. In general, 45 ACP is much more prone to manufacturing shortages, and this can significantly drive up retail prices if you can even find the products that you’re looking for.

Best Uses – Which Caliber to Use When

I could spend an entire article waxing poetic about which caliber is the premier handgun caliber, but at the end of the day, the reality is that there is no magic ammunition. Personal preference is just that, and the most important thing is to select a weapon that is comfortable for you to shoot and that you perform well with. Whatever it is that you choose, be sure to get enough range time to achieve and maintain proficiency.

With regard to my own personal choices, I would select the following:

45 ACP
Concealed Carry
Target or Range Shooting
Home Defense
Duty or Open Carry

Concealed Carry

The 9mm takes the cake here with one notable exception. Superior capacity in a smaller package wins the day almost every time. If you live in a jurisdiction with a magazine capacity restriction, then I think a fair argument exists to upgrade to 45 ACP. Being limited to 10 or fewer rounds removes the single biggest negative to the 45 ACP in a concealed carry environment. Now, that doesn’t mean that the 9mm is a bad choice with those specific circumstances just that the playing field is much more level.

Target or Range Shooting

Both of these calibers are fun to shoot, and they both perform equally well on the range. The single biggest limitation here will be your wallet size and the ability to find the ammunition of your choice. I have to score this category a tie.

Home Defense

In a semiautomatic pistol platform for home defense, I’m choosing 45 ACP every time. The slower, heavier rounds significantly lessen the risk of target or environmental over penetration, and that risk cannot be overstated in a residential environment whether you live in a single family home or an apartment style setting.

Duty or Open Carry

When it comes to duty carry, my answer is always the 9mm. With freedom from capacity restrictions, the additional ammunition becomes exponential when you factor in 2-3 additional magazines. In duty-type situations, the range of engagement tends to extend significantly at times when compared to a CCW shooting.

For openly carrying citizens not working in a uniformed law enforcement or security role, I would say the preference is yours. Full-frame pistols chambered in 45 ACP are available with 15+1 capacity in flush mount magazines, and when factoring in extended mags, greater numbers are even possible. Without the added burden of a concealable platform, the playing field again becomes much more level between the calibers.


There isn’t much to debate in the realm of competition shooting. Most of your major players are shooting 9mm, and there is a reason for that. It’s not to say that you can’t compete in 45 ACP, but 9mm may provide that slight edge to beat your competition out.

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