As a shooting instructor and long-time shooter, I have been able to try out many different guns, different calibers and even unusual systems in my life. However, I have to admit that it often doesn't go beyond the famous first impression. Usually someone comes to the seminar with an interesting caliber or a special gun or you meet them by chance during training. After a little chat about the gun, the famous question often comes up: "Can I shoot a magazine?". Once the magazine is empty, the "test" ends with an approving nod or a somewhat dismayed shake of the head. However, valid statements about advantages and disadvantages, reliable figures or impressions that may lead to concrete comparisons can hardly be derived from such occasional insights.
A closer look: 9mm Luger, 10mm Auto and .45 ACP from the SIG Sauer P320 in comparison

This should change with this article with regard to the caliber issue. The calibers available for this article – 9mm Luger, 10 mm Auto and .45 ACP – have been shot from similar guns of the same series and described in direct comparison based on my impressions of them. The focus here is on the practical and dynamic environment, i.e. rapid shot string sequences and the necessary recoil control. The test guns are from the P320 SIG Sauer model series. Although there are differences such as barrel length and trigger, the pistols are so similar that it is possible to compare the shooting performance with the different loads. In order to better understand the differences in caliber, a little prior knowledge of their history and some facts are required. The 9mm Luger was developed by Georg Luger in the early 20th century and is probably the most widely used pistol cartridge for almost all handguns in common use today. With weights of around 115 to 147 grains, the bullets achieve muzzle velocities of around 300 to 450 meters per second, with an energy of around 400 to 600 joules. The bullet types offer a comprehensive range, from copper-plated lead or full metal jacket bullets for sporting purposes to special hollow-point bullets for defence. The worldwide success of the 9mm Luger is based on the excellent combination of controllability, accuracy and energy yield, as well as its relatively low cost.

The .45 ACP was developed at the Frankford Arsenal and Colt around 1904. The development was based on the very negative experiences in the Philippine-American War. When Filipinos attacked US troops with machetes and sticks, the poor immediate stopping effect of the .38 bullets used at the time was criticised. This led to the development of a cartridge with a larger bullet cross-section. The .45 ACP has a bullet diameter of around 11.5 mm and weighs between 165 and 230 grains. The muzzle velocities are between 250 and 400 metres per second, the energy values range from around 450 to 650 joules, as always depending on the barrel length.
The 10mm Auto was developed in 1983 by handgun expert Colonel Jeff Cooper. After a highly publicised, disastrous shootout between several FBI agents equipped with 9mm Luger pistols and heavily armed criminals in 1986, the FBI introduced the 10mm Auto the following year, in 1987. However, after difficulties with strong recoil and grips that were too large for some, the cartridge was soon changed again. The bullet weights range from around 155 to 220 grains and the bullets reach muzzle velocities of between 320 and 450 metres per second. The energy yield ranges from 550 to 1,000 joules. The 10mm Auto is the most powerful test cartridge.
SIG Sauer USA P320 Compact technical specifications
Model: | SIG Sauer USA P320 Compact |
Calibre: | 9mm Luger, .45 ACP |
Magazine Capacity: | 15 rounds in 9 mm Luger, 9 rounds in .45 ACP (each + 1 cartridge) |
Dimensons (LxWxH): | 183x33x135* mm |
Barrel Length: | 3.9"/99 mm |
Twist Rate (9mm / .45): | 1:250 mm / 1:400 mm |
Trigger Pull Weight: | 3,400 g approx. |
Weight: | 740 g |
Controls: | Suitable for right/left-hand use (after repositioning the magazine release.) |
Equipment: * = Without red dot sight, optic ready, dovetailed rear sight + front sight, with white dots. M1913 Picatinny rail, spare magazine, hard case |
Test ammo from Hornady
In our test, we only used Hornady loads that are manufactured forself-defence or law enforcement use. The 9mm Luger is fitted with the 124-grain Hornady XTP bullet. The.45 ACP comes from the Critical Duty line and uses a 220-grain FlexLock bullet. The 10mm Auto has a 155-grain XTP bullet. According to the factory specifications, the 9mm Luger delivers around 460 joules. The .45 ACP would deliver around 630 joules as a +P load. The 10mm Auto, the flagship, is claimed to release an energy of almost 930 joules at 430 metres per second – that's magnum level!
Then and now: Colt Gold Cup for the SIG P320

The first centerfire pistol we owned was a Colt Gold Cup Series 70 in .45 ACP, purchased in 1999 and used for classic target shooting at 25 metres. At that time, an extremely weak reloaded target load was used. After a short time, however, I sold the gun again because the ammunition became too expensive for me. I have never owned a 10mm Auto calibre pistol myself. My entire experience was actually based on "test magazines" from fellow shooters, and the impression that can be summarised in three words: "Awesome, but expensive". The 9mm Luger, on the other hand, has become the "house and home" cartridge over the years for sport shooting, hunting, practical dynamic shooting and my shooting seminars. The excellent control over the gun when firing, the wide choice of loads, the adequate performance level and the relatively favourable price were the deciding factors. Since then, I have fired tens of thousands of rounds and have never regretted my decision to use this cartridge. In this respect, I was very excited to see how the test shooting would re-sort my personal experience and choice. I started with the 9mm Luger. And I was able to familiarise myself with the new gun. After the first box of ammunition, I had a good feel for the trigger, the grip and the recoil behaviour. Curious about the other two cartridges, I wanted to find out right away and picked up the 10mm Auto. Already thinking about the stronger recoil, I realised exactly what I so often improve with participants in our courses: the anticipation of recoil paired with bad timing! The first shot was already a little too low. As I didn't know the trigger of the SIG pistols that well yet and also had some respect for the 10mm Auto, I had pushed the first shot down when pulling the trigger in anticipation of the recoil. Shaking my head briefly at myself and returning to the basics of good shooting, the next shots were all on target. The recoil and behaviour of the gun were a bigger challenge. The performance of the 10mm Auto takes its toll here, as the gun "jumps" considerably more than with the 9mm Luger. The shooter has to show maximum concentration if he/she wants to get the gun back on target quickly after firing. After our first experience with the 10mm Auto, we moved on to the .45 ACP. The thick cartridges quickly filled the single-stack magazine. I felt quite comfortable with the first shots after my experience with the 10mm Auto. In terms of recoil, you can feel the mass in combination with slower velocity. The gun pushed a little more in recoil than the rather poisonous 10mm Auto. Compared to the 9mm Luger, recoil was noticeably stronger. For the actual comparison test, I worked through three special drills:
- Five shots at an A4-sized target from seven meters fired as quick as possible.
- Five shots fired at a target about the size of a postcard from seven meters, as fast as the sight picture and recoil control allow.
- Five pure accuracy shots at different distances.
For me, the drills represent practical and dynamic pistol shooting because they represent the field of tension of this discipline. They also test the skills required to solve the associated problems. In short, the tension between time and accuracy! If I shoot extremely fast but don't hit anything, this is worth just as little as very accurate shots that exceed the time available to me. The first drill shows how high the loss of accuracy is at maximum speed. The second drill shows the time loss between the test cartridges with the same accuracy. The third drill shows the time-independent accuracy of all cartridges.
The first exercise with the SIG Sauer P320: 7 meters, on DIN A4 target

This is where the 9mm Luger really came into its own. The pleasant recoil behaviour, the predictable movements of the gun and the confidence that the gun would return to the target almost automatically allowed for fast shot strings paired with relatively good accuracy. No hit left the intended target area during any round, and the groups were regularly much smaller. Times also levelled off between 1.00 and 1.07 seconds for the five shots. Groupings were very consistent. It was clear that the cartridge makes it easy for the shooter. The change to the more powerful cartridges brought some disillusionment. The first rounds often showed flyers outside the target. You had to concentrate one hundred per cent and any weakness in your grip, any anticipation or reaching with the shooting hand was consistently punished by poor hits. The hit pattern was a good indication of how I tried to push the gun back into the target area. The low hits are a good indication that the gun was not behaving predictably. In terms of times, it was noticeable that the rounds were slightly slower than with the 9mm Luger. Despite trying to shoot as fast as possible, the memory of the strong recoil and lack of control lingered in the back of my mind. And the average times of between 1.05 and 1.13 seconds were slightly higher than with the 9mm Luger. The difference between the 10mm Auto and the P 320 in .45 ACP, on the other hand, was hardly noticeable. This may also be due to the slightly longer barrel of the 10mm pistol in comparison.
SIG Sauer P320 in 9mm, .45 and 10 mm: second and third drills


This shows the loss of time with consistent accuracy, i.e. how long the stronger recoil and the reduced control over the gun prolongs the time for a consistent hit pattern. A postcard-sized target was selected for this purpose, which requires the shooter to have a reasonably clean rear-sight-to-front-sight ratio when building up an acceptable sight picture. In contrast to the first test, the next shot could only be fired after the sight picture had been confirmed. The 9mm Luger also showed its strengths here. Thanks to the good control and above all the predictability of the pistol movements during the shot, the sight picture could be confirmed almost in advance. The times for five shots levelled off at just under 1.20 seconds. With the 10mm Auto and the .45 ACP, I needed significantly more time to confirm the sight picture. The anticipatory confirmation of the sight picture was not always reliable, as the gun did not always behave the same in terms of recoil. The difference between the 10mm Auto and the .45 ACP was again small. The times levelled off at around 1.60 seconds. In the final accuracy test without time constraints, there were no differences between the cartridges. Once again, five-shot groups were shot at 10 and 15 meters freehand and at 20 meters supported. All cartridges showed sufficient and good accuracy for practical dynamic shooting. Only the mental aspect of somewhat greater concentration was again noticeable with the two larger calibers.
Conclusion on the comparison of the 9mm, 10 mm and .45 ACP cartridges
My fascination with large calibers waned considerably after the test. The reason: strong recoil and muzzle bouncing! It's fun to feel this energy. But the price of ammunition for 10mm Auto and .45 ACP makes effective training difficult. And apart from the financial price, the immaterial price is also not worth it for me, because the loss of time and accuracy is considerable. Especially in practical dynamic shooting, firing several shots in quick succession is a core skill. Slowing yourself down in a threat situation, slowing yourself down and shooting "a little more unhurried" in order to hit again is almost impossible to achieve. This is where the 10mm Auto and the .45 ACP make life difficult. The old adage "the best caliber is the one that gets the job done" is justified. It is not for nothing that the 9mm Luger has become so extremely popular, especially in the LE/military sector. The other two cartridges are useful where single shots or slow firing strings with very high power are required. However, this should rarely be the case in defence situations.