Let us first start off by saying that we know that this article will kick up it’s fair share of controversy. With that being said, we’ve made our choice and it’s up to you to make your choice on which side of the fence you will fall. Both calibers have their advantages in certain situations, and both have their drawbacks. Let’s go ahead and jump in head first. If you’re looking for a handgun to keep you alive in a survival situation you want it to be one that’s utterly dependable. It needs to be easy to use, reliable and it needs to be chambered for an effective round. Smaller calibers like the .380 or the .22 may hold some merit, but for our money, we are sticking to the top two choices in the United States. It’s that last point that makes all the difference but it’s also the most controversial. There’s a big range of handgun calibers out there, but about a dozen of them account for most pistols in use. Each of these rounds has its good and bad points, and a lot of the time it’s just a matter of personal preference, but some are more effective than others and making the right choice can increase your chances of survival. Worldwide, the primary caliber that stands head and shoulders above all others is the 9mm Parabellum. It’s the NATO standard, the choice of most police departments across the globe and since the fall of the Iron Curtain is even taking over the market in the former communist nations. In most countries, if you want an effective and powerful handgun a modern 9mm is the obvious choice. The big exception is the USA; among American shooters there are several popular rivals to the ubiquitous nine and, again, one stands out from the crowd. That’s the iconic 20th century American pistol round, the .45 Automatic Colt Pistol. History of the Rounds: The .45 ACP and 9mm rounds both date from the same period – the first decade of the 20th century – when many nations were looking at replacing revolvers with semiautomatics. The 9mm was eventually adopted in the P08 “Luger” while John Browning developed a series of .45 autos that ended with the legendary M1911. Since then the calibers have been engaged in a struggle that almost rivals the wars they’ve been used in. Globally the 9mm has been a clear winner, with few countries now using the .45 as a military cartridge, and even in the USA it’s made major inroads; it’s been the US military’s standard pistol cartridge for 30 years. Many American shooters have resisted the change though, so any discussion of which is the survival round is inevitably going to be controversial. Anyway, let’s compare the facts. Round Comparisons: Look at the two rounds side by side and it’s obvious the .45 ACP is physically much larger. The case is longer, at 22.8mm compared to the 9mm’s 19mm. Bullet diameter is also greater at 11.43mm; it’s a much bigger step up than going from a nine to a .40 S&W, for example. Overall length for the .45 is 32.4mm compared to 29.69mm for the German round. Round Velocities Compared & Explained: Don’t jump to conclusions based on size, though. What decides the effectiveness of any bullet is how much energy it dumps into the target, and how quickly it does it. The energy the bullet carries is a product of its weight and velocity, with velocity having a lot more of an effect; how rapidly it transfers that energy into the target comes down almost entirely to the way it’s designed. The .45 starts out with an obvious advantage here; the bullet it launches is bigger and heavier. The standard US military load carried a 230 grain full metal jacket round; most military 9mm bullets are half that weight, 115 grain. Commercial 9mm is usually close to that figure as well although some heavier ones are available, up to around 147 grain. Commercial .45 ACP bullets are usually in the 185 grain range but military weights are popular too. Clearly, everything else being equal, a .45 bullet is going to have more of an effect on your target than a 9mm. It’s not that clear-cut though. The problem is that everything else isn’t equal. The equation for kinetic energy – the amount of energy your bullet hits the target with – is 0.5 x Mass x Velocity2. Energy increases linearly with mass, but exponentially with velocity. To double the energy you need to increase bullet weight by 100%, but you get the same effect by increasing its velocity just over 41%. The way to get higher velocity is by increasing the pressure of the burning propellant and the .45 is a low pressure round; maximum case pressure is rated at 21,000 psi for standard loads and 23,000 psi for +P. The 9mm is a high-pressure round; it can handle up to 35,000 psi, or 38,500 psi in +P. That difference has a major impact on bullet velocity. GI ball ammunition, with the 230 grain bullet, leaves the barrel at 830fps for a muzzle energy of 352 ft lbs. Compare that with a typical 9mm 115 grain FMJ; its velocity is 1,300 fps, 56% higher than the .45, and the muzzle energy is 420 ft lb. So, despite firing a smaller, lighter bullet, 9mm Parabellum is a significantly powerful round. Loading the .45 with a lighter (and faster) bullet can do a lot to increase the power, and it’s not hard to achieve over 450 ft lb, but there are hotter 9mm loads too. In practice the most powerful .45 +P+ deliver about 616 ft lb, but some 9mm loadings reach 680 ft lb. Simple physics gives the 9mm a clear power advantage over the heavier but slower .45. A lot of .45 fans are going to disagree with this being that one of the keystones of firearms folklore is that the big Colt bullet has enormous knockdown power compared to smaller cartridges. They’re not exactly wrong, either. The 9mm carries a lot more energy but it also has to dump it when it gets to where it’s going; if your bullet passes right through the target it’s taking wasted energy with it. Where the bullet stops in the target, one that penetrates deeply and dumps energy slowly won’t be as effective as one that delivers it all more or less instantly, and often this factor gives the .45 a real advantage. A lot of the combat experience that started the legend of .45’ superior stopping power came from the World Wars, when both sides were using standard FMJ ammo. Military FMJ rounds have high penetration and both calibers stood a good change of blowing through the target, but 9mm was much more likely to. Even if it did pass right through the bigger .45 bullet created a larger wound channel, more damage and more bleeding; that was almost certainly going to stop the target quicker. Using FMJ ammo there’s no way to prevent the 9mm from overpenetrating; more energy behind a smaller diameter bullet means it’s going to penetrate more. If your only option is military ball ammo the .45 closes the effectiveness gap and probably takes the lead. On the other hand, in a survival situation you’re not limited to military ball, and you’re free to load expanding ammunition in either caliber. That resolves the penetration issue and gives the advantage back to 9mm. So ballistically the 9mm is the superior cartridge, but that’s not the only factor we need to look at. One that’s often overlooked is ammunition availability; in a long-term survival situation that can become important, because without a steady supply of ammo your trusty pistol becomes a badly balanced hammer. In most cases 9mm has a clear edge here because it’s so used; any police department, US military unit or ammo dealer will have a large supply. Compared to .45 in the USA, however, this isn’t such a big deal; you’re not going to have any trouble finding either of them. Common Capacity Comparisons: Moving on to ammunition capacity there’s no contest – 9mm wins. The most popular .45 design by a long way is still the classic 1911, which takes a seven-round magazine as standard. The 9mm weapons the Germans used in both wars held eight rounds, so there wasn’t much of a difference, but things were already changing; the Browning Hi-Power, with its 13-round capacity, went into production in 1935 and was used by the British and Canadians (and the Germans, who’d captured the original factory) during the war. Most modern full-size 9mm handguns hold 15 rounds or upwards and a standard .45 can’t match that. There are .45s that use large-capacity double stack magazines – the Glock 21 holds 13 rounds, compared to 17 in the 9mm version – but doubling up on the long, fat cartridges makes for a bulky grip that isn’t comfortable for small, or even average, hands. It also has a real penalty for concealment, although a single-column .45 will often be flatter and easier to hide than a high-capacity 9mm – the 1911 is a big gun, but it’s a third of an inch slimmer than a SIG P226. Lastly there’s ease of use. Although the round is less powerful, the heavy bullet and generally heavier weapons mean the .45 has considerably more recoil than an equivalent 9mm. This can slow down a follow-up shot; with a nine it’s easy to rapidly double-tap and also easier to learn with if you are a beginner. There are advantages both ways though. The recoil of a .45 is heavy, but it isn’t as sharp. If you have a light build you’re probably going to get on better with a 9mm, but for older or disabled shooters who don’t have a lot of wrist strength it can pay to opt for a .45. Wrap Up & What We’d Choose: So overall – and this is going to upset a lot of people – 9mm Parabellum beats .45 ACP in our opinion as a survival caliber. It’s more powerful, hits harder with decent modern bullets, it’s generally more controllable and you can pack more rounds into a magazine. It’s easy to find ammo and there’s a wider choice of weapons available. The .45 ACP is also effective, though, and depending on what you’re looking for it could suit you. Either one of these old rounds will serve you well, which is why they’re still the top two choices after more than a century.