The .357 SIG was designed to duplicate the ballistics of the 125 grain loading in a .357 Magnum, the round generally credited with the highest percentage of one-shot-stops. Being a bottlenecked round, it is also less likely to have feeding/chambering issues. It's a great round for which I do not own any guns in that caliber.
SIG also makes a great handgun.
LEO cartridges underwent a tumultuous period following the infamous FBI Miami Shootout, of which, cartridge failure (9mm) was a major factor eventually prompting the FBI to go to the 10mm short-stack for a period while the .40 S&W was secretly on the drawing boards. The .40 got there first and ran away with the show. Nevertheless, you don't want to find yourself at the wrong end of a .357 SIG.
I agree the FBI adopted the 10mm due to concerns about 9mm performance, but the .40 S&W wasn't secretly in development -0 it was just a natural evolution to allow the same performance in a smaller pistol.
The FBI held a seminar on wound ballistics at Quantico in September 1987 with the primary purpose of identifying the performance criteria needed to inflict an incapacitating wound on a human target with a handgun bullet.
A second purpose of the seminar was to determine, whether the 9mm or the .45, was most effective in achieving rapid incapacitation. The seminar failed to resolve the caliber dispute but it did outline the performance criteria of an effective bullet. The key finding in incapacitation was that whether by means of a CNS hit or by means of rapid loos of blood pressure, the bullet needed to have adequate penetration to achieve either method.
That led to ballistic testing with bare gelatin, light clothing, heavy clothing (not the much simplified 4 layer denim test), and barrier penetration with 20 ga steel wall board, windshield glass, and plywood. The loads used were a 9mm 147 gr sub sonic load from Winchester and a .45 ACP 185 gr load from Remington, both selected based on the results of the wound ballistics seminar.
However, the then new 10mm was evaluated in preliminary tests for possible inclusion in the final testing given that it fell in between the 9mm and .45 calibers. The FBI found that performance of the full power commercial rounds was excellent - but the recoil and muzzle blast was excessive and offset much of the performance advantage. The end result was the FBI loaded down the round with a 180 gr bullet at 950 fps - essentially what became the "FBI Lite" or "FBI Medium" load with velocity between 950 and 980 fps with a 180 gr bullet. .
That round performed well with both penetration and wound volume with the 18" limit equal to the .45 ACP and significantly superior to the 9mm as well as the .38 + control round. The 10mm was also much more accurate than any of the other rounds. It also achieved penetration at or in excess of 12" 97% of the time, compared to 92% for the .45 and 67% for the 9mm and .38 +P loads. (40 shot samples were used in testing).
The 10mm "Lite" or "Medium" load was thus adopted. However it didn't take long for all involved to recognize the reduced powder charge could be accommodated in a shorter case that would fit existing 9mm sized pistols. Thus the .40 S&W was born - designed specifically to launch a 10mm 180 gr bullet at 950-980 fps in a 9mm frame sized handgun.
The .40 S&W wasn't developed in secrecy, and it's sales superiority compared to the 10mm using medium loads lies in it's ability to be used in a smaller 9mm sized handgun.
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It's not all good however.
The .40 S&W costs magazine capacity and the recoil is heavier, which results in slower doubles and controlled pairs. It also is much more prone than the average handgun caliber to pressure spikes caused by set back, particularly in the 180 gr loading.
It's also worth noting that the 10mm FBI and .40 S&W loads' 180 gr bullet at 950-980 fps is virtually identical to the black powder .38-40 load when fired in a pistol. In other words, if you put a modern .40 hollow point in the old black powder loaded .38-40 from the 1870's you'd get the same performance.
The point here being that more velocity isn't always better and after 120 years of handgun cartridge evolution, the only thing that really changes was the design of the bullet - the velocity and weight were pretty much the same.
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The .357 Sig uses the 10mm as it's parent case and is about .009" longer than the .40 S&W case. most self defense loads will launch a 125 gr bullet at between 1,350 and 1,450 fps.
That compares to the 10mm's velocity of around 1,600 fps with a 135 gr bullet and 1,300 fps and 1400 fps respectively for 180 gr and 165 gr bullets.
The .40 S&W clocks 980 fps with a 180 gr bullet and turn in around 1400 fps with a 115 gr bullet.
The above numbers compare to around 1,225 fps for a 125 gr 9mm +P and 1,150 fps for a standard pressure 125 gr 9mm.
So...the .357 Sig is a lot less than a 10mm in both bullet diameter and bullet weight when velocities are comparable. It's about equal to the .40 S&W in velocity when bullet weights are similar, but still has less bullet diameter while hindered by the same case diameter giving it identical magazine capacity. Finally, the .357 Sig offers 200-300 fps more velocity than a 125 gr 9mm round.
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The biggest question is whether a 200-300 fps velocity advantage over a 9mm Luger makes a difference. I'll argue it does not.
There are a couple major problems with using the FBI's late 1980s and early 1990s conclusions on 9mm Luger effectiveness.
First, the FBI was heavily biased toward the heavy but slow 147 gr round in the 9mm, and the 147 gr hollow points of the day performed very poorly. More often than not they didn;t expand and just penetrated like an FMJ. The FBI's obsession with penetration meant they didn't see the problem with that. However lighter, faster, 124-125 gr hollow points that were more likely to expand and still meet the 12" minimum made more sense even then.
Second, 9mm hollow point design and performance has improved dramatically in the 30 years since the Miami shootout.
As noted above, more velocity isn't always better. In fact, in testing the original 10mm, .45 ACP and 9mm loads the FBI used standard SAAMI test barrels. However the standard test barrel length for 9mm is 4" while it is 6" for the 10mm and the .45 ACP. The FBI debated this but stayed with the longer lengths in the 10mm and .45 ACP as it found that penetration was actual reduced with the longer barrel due to the more rapid expansion that occurs with the higher velocity. As such they felt the longer barrels were a disadvantage for the 10mm and .45 ACP in the penetration tests and thus retained them in testing. (They probably boosted the wound volume results a bit, but it didn't matter as the FBI's primary focus was on penetration).
That, along with loading down the 10mm in the first place, is the long way of saying more velocity isn't always better.
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Not surprisingly the FBI is moving back to the 9mm, and if you read the executive summary of their decision paper you'll see this:
- Caliber debates have existed in law enforcement for decades
Most of what is "common knowledge" with ammunition and its effects on the human target are rooted in myth and folklore
- Projectiles are what ultimately wound our adversaries and the projectile needs to be the basis for the discussion on what "caliber" is best
- In all the major law enforcement calibers there exist projectiles which have a high likelihood of failing LEO's in a shooting incident and there are projectiles which have a high likelihood of succeeding for LEO's in a shooting incident
- Handgun stopping power is simply a myth
- The single most important factor in effectively wounding a human target is to have penetration to a scientifically valid depth (FBI uses 12" – 18")
- LEO's miss between 70 – 80 percent of the shots fired during a shooting incident
- Contemporary projectiles (since 2007) have dramatically increased the terminal effectiveness of many premium line law enforcement projectiles (emphasis on the 9mm Luger offerings)
- 9mm Luger now offers select projectiles which are, under identical testing conditions, are outperforming most of the premium line .40 S&W and .45 Auto projectiles tested by the FBI
- 9mm Luger offers higher magazine capacities, less recoil, lower cost (both in ammunition and wear on the weapons) and higher functional reliability rates (in FBI weapons)
- The majority of FBI shooters are both FASTER in shot strings fired and more ACCURATE with shooting a 9mm Luger vs shooting a .40 S&W (similar sized weapons)
- There is little to no noticeable difference in the wound tracks between premium line law Auto enforcement projectiles from 9mm Luger through the .45 Auto
- Given contemporary bullet construction, LEO's can field (with proper bullet selection) 9mm Lugers with all of the terminal performance potential of any other law enforcement pistol caliber with none of the disadvantages present with the "larger" calibers
Many of those comments are relevant to the .40 S&W and the .357 Sig - namely that they are not any more effective in meeting the FBI's criteria, and have downsides in terms of reduced magazine capacity, higher recoil and slower shot string times.
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I do agree that in most local law enforcement agencies the selection of caliber and pistol often comes down to the preferences and influences of a couple key people in the agency.
For example, I was shooting with a newly hired officer from the Kinston NC police dept, a couple months ago and that officer was shooting a .357 Sig that didn't fit the officers hands very well and over all hindered the officer's effectiveness in shooting it. After some discussion it became obvious that the caliber and pistol selection came down to the preference of a single influential officer a few year prior who happened to like both the .357 Sig and the Sig P226.
Is it a good choice for general issue? Probably not, particularly for officers with smaller hands, but that wasn't a factor in the selection "process".
