.32 ACP History
The massive rise in semi-auto pistols during the 20th century owes much to the work of one man, John Moses Browning. Browning’s genius for firearms designs is well known, but his contributions to the world of semi-auto ammunition is far less talked about. His first pistol cartridge, .32 ACP (Automatic Colt Pistol), set the stage for many to follow.
In the late 19th century, Browning had two particular problems that helped lead to the creation of the .32 ACP. First, he was constantly under the thumb of the major American firearms manufacturers Colt and Winchester, which both worked in unison to buy up as many of Browning’s patents as possible to curb competition. Second, traditional rimmed handgun cartridges were ill-suited for semi-auto handguns using box magazines.
In 1897, Browning shared his work on a new semi-auto pistol with a representative of Fabrique Nationale Herstal (FN) out of Belgium. Known more for its bicycles than firearms, FN’s partnership with Browning would prove beyond fruitful. A few years later, FN released the Browning-designed blowback M1899 chambered for the new 7.65x17mmSR Browning, also known as 7.65mm Browning Short or .32 ACP.
The improved M1900 that followed saw a total production of somewhere around 700,000 pistols over 11 years. However, the real success was the .32 ACP cartridge.
The .32 ACP had a straight-wall design with a semi-rimmed case. The straight wall made it suitable for reliable operation inside a semi-auto blowback pistol. The semi-rimmed case made feeding the round from a box magazine more reliable than fully rimmed cases. It also allowed each round to be headspaced off the small rim. More on that later.
It's hard to overstate just how rapidly .32 ACP took off as a favorite semi-auto cartridge. You could almost think of it as the 9mm of its age, and it sparked an arms race among gun designers. Other firearms designed around the tiny round sprang up in droves over the first half of the 20th century, including the famed Walther PP (1929), Colt 1903 Pocket Hammerless, Mauser HSc (1940), and the Savage 1907/1917.
Related: German Mauser HSc Pistol Review – Captured German History
Related: Savage Model 1907 & 1917 – The 1911’s Forgotten Nemesis?
The round found favor with many nations’ militaries, and it served extensively through both World Wars. But the small size and low recoil of the little .32 ACP also made it a favorite on the consumer market.
Drawing on his work when developing the .32 ACP, Browning went on to design a host of other pistol cartridges that ranged from the even smaller semi-rimmed .25 ACP to the larger .380 ACP and .45 ACP. The latter two did away with the semi-rimmed design.
Even with the rise of the newer 9mm Luger, which also shares many of the same basic design features, the miniscule .32 ACP continued to serve as a popular option for European militaries and police well into the second half of the 20th century.
Ballistics & Specs
I won’t sugar coat it. The .32 ACP is a small round with limited power that matches its diminutive stature. It’s not a tiny magic bullet. That’s especially true when compared to the far harder hitting 9mm, .40 S&W, .45 ACP, and 10mm rounds that dominate much of today’s preferred self-defense chamberings. But don’t dismiss it as unworthy just yet.
A key feature of Browning’s .32 ACP design was the use of the semi-rimmed case. This served a specific purpose for headspacing and feeding. Headspace is the distance measured between the breach face relative to the internal chamber of a firearm that limits how far a cartridge goes into the chamber.
Most handguns of the time used some form of rimmed cartridge, which is great for a revolver-type design but creates feeding issues when the rimmed rounds are stacked on top of each other inside a box magazine. The semi-rim design improved feeding for the .32 ACP, but the small rim did still leave the possibility of a “rim lock” malfunction. That’s when the rim of one case inside the magazine locks with the rim of another case and causes a malfunction.
Since a straight-walled cartridge doesn’t have any shoulders – the angle created when a bottlenecked cartridge narrows near the front of the case – the semi-rimmed case on the little .32 ACP still allowed it to headspace off the narrow rim. Browning’s later .380 ACP and .45 ACP casings did away with the rim entirely and headspaced off the forward lip of the larger cases instead.
Browning designed the .32 ACP as a centerfire cartridge, which improved reliability over small rimfire rounds like your common .22 LR plinking ammo. The straight wall of the case is .337 inches in diameter, leaving just enough room for the .3125-diameter bullet. Cartridge lengths will very slightly depending on the type of bullet used, but generally fall just under an inch.
The semi-rim measures slightly wider than the rest of the case at .358 inches in diameter with a thickness of just 0.045 inches. As small as that is, Browning went even smaller with his later .25 ACP semi-rimmed cartridge. Here’s a quick look at the .32 ACP's smaller and larger peers, .25 ACP and .380 ACP:
Bullet weights normally fall between 60 and 73 grains. You can compare that to the common 50-grain .25 ACP and 95-grain .380. Here is some ballistics data comparing .25 ACP, .32 ACP, and .380 ACP with similar bullet types within a reasonable 25-yard distance.
None of these rounds were meant for long-range shooting or to provide impressive terminal performance at long ranges. So, I’m not terribly interested in things like bullet drop or energy beyond realistic self-defense distances within 25 yards.
Obviously, the .380 ACP dominates both the smaller cartridges in energy and velocity. It also drops impressively little at 25 yards, just around 1 inch compared to the .32 ACP’s nearly 2 inches of drop. But from the perspective of self-defense shooting within that range, it’s a fairly minimal difference.
The .32 ACP basically doubles the performance of the smaller .25 ACP at every distance between 0 and 25 yards for foot-pounds of energy. The same is note quite true for the .380, which has right around 45 percent more energy at the muzzle and 43 percent more at 25 yards.
Related: .380 ACP vs 9mm for Self-Defense – What’s the Real Difference?
Tools&Targets has a nice breakdown of the performance differences between .32 ACP and .380 ACP when tested in ballistic gel. Suffice it to say that the .380 offers a lot more in terminal performance with larger wound channels and slightly deeper penetration. But the .32 ACP isn’t a slouch for such a small caliber.
The smaller size also makes the round incredibly light recoiling, and you can squeeze a few more rounds of .32 ACP than .380 ACP into a similar-sized magazine. What you get with .32 ACP is more or less what you would guess. It has less power but also very low recoil. Yet, it still had enough stopping potential to earn it a place in many military holsters and consumers’ pockets for much of the 20th century.
Modern .32 ACP Firearms
It’s not a common chambering these days, but there are plenty of current-production firearms that still run the pipsqueak .32-caliber pills. We recently reviewed a Beretta 3032 Tomcat, which also features a tip-up barrel so you never have to rack the slide to load or unload the very small gun.
Related: Beretta 3032 Tomcat Purrs With a Suppressor
The .32 ACP seems to have found a nice niche of its own in modern mouse guns. There’s the incredibly light and small KelTec P32 that has been in production since 1999, and the Seecamp LWS 32 (1985) and NAA Guardian (1997) are still rolling out to this day. All are popular options as backup guns and pocket pistols.
During the Cold War, the size and low recoil of the .32 ACP even helped it find a place in submachine gun history with the zippy Czech vz. 61 Skorpion (1959). A lot of other Cold War-era .32 ACP pistols from the other side of the Iron Curtain found their way into the U.S. commercial market over the last several decades as well and can still be found on the surplus market.
Pros & Cons
Here’s my short list of the pros and cons for the .32 ACP cartridge:
Pros:
- Very low recoil
- Higher capacities due to small size
- Very concealable firearm options
- Enjoyable to shoot
- Lots of cool history
- More reliable than rimfire cartridges
- Still decent ammo availability
- Nice backup gun options
Cons:
- Ammo is pricier these days
- Lower power
-
Possibility of rim lock
Final Thoughts
I wouldn’t say .32 ACP is a preferred round for self-defense. It’s small, and that’s reflected in its theoretical “stopping power” – shot placement always counts folks. But I would certainly prefer having a handgun chambered in .32 ACP over a lot of other options.
I’ve also found that guns chambered for the low-recoiling cartridge are easy to shoot and often offer improvements in accuracy for follow-up shots over larger calibers. Best of all, they are usually very, very small. That makes them easy to conceal and surprisingly fun to shoot.
Regardless, there’s no denying the .32 ACP has a well-earned place as one of the most influential rounds from the last century. It had a huge impact, even if it is under an inch tall.
