Since its inception, the 10mm round has struggled compared to other rounds on the market like the 9mm and .45 ACP. Originally conceived as a magnum semi-automatic round in 1983, it was quickly drawn into consideration as a replacement for the 9mm. Due to multiple events in the 1980s, there was a perceived need for a more powerful round for policing. The 10mm, along with the .40 S&W (coming out in 1990), were both seen as potential solutions.
Though the 10mm was briefly considered for this role, the .40 S&W became the new round of choice for the FBI and many police departments throughout the United States. The 10mm weathered this storm and, due to exposure on shows like Miami Vice and availability of the Colt Delta Elite in 10mm, it remained a viable round for those looking for something with a higher power factor in a semi-automatic round.
The 10mm has remained a mainstay in smaller releases. Colt and Kimber often chamber 1911’s in the round while Glock released a line of firearms specifically chambered in 10mm including the Glock 29 (subcompact), Glock 20 (full frame), and Glock 40 (long slide). Though the 10mm never enjoyed the success of the .40 S&W, it saw multiple releases as a hunting or civilian-defense round. A common chambering in pistol caliber carbines (PCCs), the 10mm’s ballistics are well-suited to a longer-barreled gun. Today, with companies offering a wider array of civilian handguns to meet the growing markets, it seems like 10mm is well-placed to see another resurgence.
Civilian Use: How to Evaluate Your Carry
For about five years, I carried a 10mm as my primary civilian carry. Prior to this change, I carried .45 ACP as I have a hard-wired bias favoring larger rounds. When I shifted from .45 ACP (IWI Jericho and Colt 1911) to the 10mm, I also transitioned from metal-framed external hammer guns to polymer striker-fired guns. This change, driven mainly by my sports medicine doctor, was to improve my back pain through carrying a lighter gun. Though I considered staying with .45 ACP, I decided to go all in on the recommended change.
This change wasn’t just a gut feeling or solely based off medical advice; I also based it on research and practical experience tests. I researched the capacity and ballistics of each round and found the 10mm offered more capacity (15 rounds of 10mm instead of 13 rounds of .45 ACP in the Glock full frame) and better ballistics. Next, I compared my personal draw time and ability to place three rounds within a 4” circle at 21 feet. At the time, I had no meaningful difference in speed and accuracy comparing the 10mm Glock 20 to the .45 ACP Glock 21. Thus, the Glock 20 in 10mm became my primary carry and the subcompact Glock 29 (also in 10mm) my deeper concealment gun.
Increase in Practice Shooting and a Re-Evaluation of the 10mm
Multiple factors conspired to move me away from 10mm as my primary carry round. The strongest influence was purely monetary. As I started to shoot and train more, the cost of 10mm over 9mm became a strain. The first time I considered changing, I ran a series of timed tests as I did before. This time, I compared three rounds of 10mm at 21 feet to three rounds of 9mm. While I was slightly faster with the 9mm, I remained with my 10mm for the moment.
As the differences in price continued to expand, I started competing more with 9mm. At the start of 2020, the severe lack of available rounds resulted in my training with 9mm since it’s what I had stockpiled. The final decision occurred in early 2021. As my timed test showed, I didn’t slow down shooting three rounds of 10mm but was significantly faster with 9mm, likely due to competition and training. I changed from 10mm to 9mm and continue carrying 9mm to this day. This was the right choice for me, but what about for others?
Putting the 10mm to the Test
I believe to this day that:
1) Any gun is better than no gun,
2) Bigger, faster bullets are better in a one-on-one comparison, but
3) You also need to manage multiple shots effectively (speed and accuracy), and
4) More capacity is better than less capacity.
Balancing these thoughts with concerns for reasonable concealment results in a very personal choice. Experiences and data-driven ballistic comparisons should help mold that choice. As such, I compared three full frame semi-automatic handguns: the Glock 17 (9mm), 21 (.45 ACP) and 20 (10mm). I also examined the same three rounds in the Glock subcompacts (Glock 26, 30, and 29).
Table 1 is a comparison of these guns’ dimensions, weight, and standard capacity. I then looked at ballistic data from all six guns examining bullet weight (all Federal Premium HST), feet per second at muzzle (FPS), power factor (Grain weight multiplied by velocity2 divided by 450,437), and finally total power (power factor X capacity).
The G17 is slightly smaller than either the G20 or G21 versions. However, there is almost no difference between the .45 ACP and 10mm. From my own experiences, the size and weight differences between all three are very minor (amounting to less than a tenth of an inch and 6-8 ounces). When looking at each cartridge’s power factor, there’s an approximate 20% gain from 9mm to .45 ACP and 36% gain to 10mm. For total power, there isn’t much difference comparing the 9mm G17 to the .45 ACP G21. Though each .45 round has more power, the G17 actually has a slightly higher total power with its larger capacity. However, the Glock 20 is the clear winner with an approximate 28% increase over either the Glock 17 or 21.
Conclusions
The 10mm still provides a reliable high-power handgun round in a semi-automatic platform with near 9mm capacities in similar guns. The question is: how quickly and accurately can you fire a 10mm compared to a 9mm version? If I can choose between faster and heavier rounds placed just as accurately in a similar span of time, then the question becomes one of concealment and capacity (and perhaps worries of over-penetration). Make sure you carry the gun that works for you and, if possible, put that to the test to make the decision that is right for you.
