The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

.40 S&W / 10x22mm S&W

.40 Flat-nose FMJ

The .40S&W was invented after the 9mm bullets that were the standard issue for FBI agents failed to perform as desired during the infamous 1986 Miami shootout. The detals of that are interesting but not pertinent, other than it led to the trial and search for a replacement.

Initially, a 10mm Auto was selected, butt that made for a large-frame pistol and packed a pretty significant whollop. Having personally shot a 10mm, I can attest to this – it’s a handful.

During ballistic tests, it was found that a 10mm 180gr projectile loaded to about 950fps met the criteria for wound channel and penetration depth. That left a lot of air in the 10x25mm (10mmAuto) case, so downsizing it to 10x22mm let the package fit into a 9mm pistol frame. The cartridge debuted in January 1990.

The basic inputs will be driven from a 180gr JHP bullet that matches the standard projectile initially developed for the FBI, selected as a higher energy load that expands well. This provides a healthy energy load . . . but not the most energetic available (which GURPS favors due to conversion factors).

Precis – The Reloading Press weekly feature writes up the .40S&W pistol cartridge.

Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 100mm for the (test) barrel length.

Chamber Pressure 34000
Barrel bore 10
Case Length 21
Chamber Bore 10
Barrel length 100
Bullet Mass 180
Aspect Ratio 1.8
Burn length 3.81
Projectile Caliber 10
Total Accelerated Mass 180
Expansion Ratio 1.78
Projectile Load 1

Output Stats

Selected Gel Impact Tracks

This cartridge is designed to be an intermediate in many ways. Intermediate in caliber between 9mm and .45ACP, intermediate in velocity between the 1250fps of the 9mm and the 800fps of the standard .45 ACP.

This one is a 180gr projetile at 995 fps out of a 100mm barrel, which will do even better out of the 5″ full-sized pistol. More on that later, but here’s the chart showing how damage changes with barrel length.

  • The velocity is at the muzzle. The velocity with a 4″ (100mm) test barrel is tuned to match real-world data at 995 fps with a 180gr JHP bullet. This is not the highest energy .40 available, but it’s pretty good, and within the original FBI specs, so it’s what I chose.
  • Out of a full-sized, 5″ barrel such as the M9 pistol (Beretta M92, or M96 when it’s in .40) there’s no real reason to use a 9mm in GURPS. More on that later.
  • The breakpoint for pi+ in GURPS is currently at 10mm/.40″. You can see that’s a bit generous, as the bullet modeled would be better at closer to +1 per die.
Some more notes on barrel length. There are really two practical lengths for pistols here. The 3-4″ set will deliver 2d+1 damage. The full-sized pistol with a 5″/127mm barrel hits 2d+2. SMG barrels between 6.5 and 11″ long will get 3d-1. After that, carbine-length barrels will eke out 3d.

The JHP with modern design is quite impressive, expanding in this case to 1.77x its starting diameter – and there are commercially-available loads that will expand to a full 2x the starting diameter, though they’re slightly slower. With the model the less-expanding and faster one is better, though. That will do 2d with  calculated 2.4 wound channel modifier. That won’t translate into usable criteria in 4e, as damage tops out at pi++. Still, most .40 weapons will hold 10-13 rounds in a concealable, accurate package that will do 2d pi++, getting the penetration of a 9mm JHP (2d) but the wounding of a .45 ACP JHP (pi++).

Alternate Loads

As noted earlier, the load chosen isn’t the only load, nor is it the “best” from a GURPS conversion standpoint. There are some very impressive loads in JHP (typical self-defense loads, but not military style stuff) in the table below.

The hottest load will do 2d+2 even out of a 4″ barrel, expands to 1.65x (0.66″), and hits the right breakpoints to get 2d+1 pi++ out of a JHP. That’s about as good as you can eke out of a hollow-point round.

Penetration in gelatin of various commercial JHP rounds

In the FMJ category, there are some hot, hot loads out there that require  fully-supported chamber to fire properly. The Glock 22 and 23, for example, were partially supported, and could do nasty things with this ammo.

But if you have the right platform, there are 155gr bullets that zip along at 1300fps (3d), and a very fast 135gr bullet at 1500fps that also does 3d, but is light-weight enough to drop from 1.2 to 1.1, which drops it out of any contention for pi+.


Springfield XD(M) with extended mag

There are a huge number of handguns chambered for the .40S&W – it rapidly became one of the most, if not the most, popular chambering for self-defense and law-enforcement weapons – at least recently and in the USA.

Pocket pistols with a 3″ barrel such as the S&W M&P Shield, a few different Kahr pistols, and the 3″ or 3.3″ barrel Springfield XDs will hold 6-7 rounds in single-stack versions, and the XD double-stack holds 9.

The more common 3.8-4″ service pistols blend concealability with 11 rounds in a flush-fit mag, and 15 or 16 in an extended configuration, which is easy on the grip but much less concealable. Glock 22s hold 15 rounds, while Glock 23s are 13.

Springfield XD and Kahr (bottom) 3″ barrels

Full-sized service pistols with 4-5″ barrels still only eke out 2d+1 until you hit the full 5″ barrel, such as in the Beretta M96.

For SMGs, there are of course the usual offerings from Heckler and Koch – the MP5 and UMP. Sig Sauer makes a cool-looking one with an 8″ barrel, which is pretty common for SMG-length weapons.

Finally, carbine-length weapons do exist, with barrel lengths that will tend to be in the 16″ range, but nearly anything in that regime will be identical for stats until one hits too-long barrels in which the bullet will have long-since past the point where the bullet is more slowed by friction than it is accelerated by expanding powder gas.

Sig Sauer SMG

Ultimately, the .40S&W is a nearly magical cartridge for pistols in GURPS. It hits all the breakpoints that GURPS has, allowing for good capacity, good damage, and excellent wounding.

The (0.5) armor divisor that standard rules gives really tamps this down from a “wears any armor and you’re very well proteeted” perspective. If you use the decimal multipliers, though, it occupies a nice space. 20% more injury, about equal penetration, but modern JHP ammunition expands to feasome diameters, easily meriting the pi++ designation given by my system.

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